From 633f5364041cd4aec7fe486dc3524c0f96006ef6 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Fri, 17 Jan 2025 17:08:49 +1000
Subject: [PATCH 01/22] Implement usermode (WIP)

---
 kernel/CMakeLists.txt                      |   1 +
 kernel/src/arch/x86_64/usermode/usermode.c |  86 +++++++++++++++++
 kernel/src/arch/x86_64/usermode/usermode.h | 103 +++++++++++++++++++++
 kernel/src/kernel_main.c                   |  15 ++-
 4 files changed, 200 insertions(+), 5 deletions(-)
 create mode 100644 kernel/src/arch/x86_64/usermode/usermode.c
 create mode 100644 kernel/src/arch/x86_64/usermode/usermode.h

diff --git a/kernel/CMakeLists.txt b/kernel/CMakeLists.txt
index d3f2c0e..4b03a54 100644
--- a/kernel/CMakeLists.txt
+++ b/kernel/CMakeLists.txt
@@ -31,6 +31,7 @@ add_executable(kernel
         src/arch/x86_64/klib/klib.c
         src/arch/x86_64/klib/malloc.c
         src/arch/x86_64/serial/serial.c
+        src/arch/x86_64/usermode/usermode.c
         src/arch/x86_64/vga/vga.c
         src/kernel_main.c
         src/io.c
diff --git a/kernel/src/arch/x86_64/usermode/usermode.c b/kernel/src/arch/x86_64/usermode/usermode.c
new file mode 100644
index 0000000..947207f
--- /dev/null
+++ b/kernel/src/arch/x86_64/usermode/usermode.c
@@ -0,0 +1,86 @@
+#include "usermode.h"
+
+static struct gdt gdt = {0};
+static struct tss_entry tss = {0};
+
+static uint8_t ist1_stack[4096];
+static uint8_t ist2_stack[4096];
+static uint8_t rsp0_stack[4096];
+
+void enter_usermode(void *function_address) {
+    struct gdt_entry *ring3_code = &gdt.code;
+    struct gdt_entry *ring3_data = &gdt.data;
+
+    // ! EVERYTHING NOT SET IS ZERO !
+    ring3_code->limit_low = 0xFFFF;
+
+    ring3_code->read_write = 1;
+    ring3_code->code = 1;
+    ring3_code->code_data_segment = 1;
+    // ring 3
+    ring3_code->DPL = 3;
+    ring3_code->present = 1;
+    ring3_code->limit_high = 0xF;
+    ring3_code->available = 1;
+    ring3_code->long_mode = 1;
+    ring3_code->big = 1;
+    ring3_code->gran = 1;
+
+    // data is basically the same besides the code bit
+    *ring3_data = *ring3_code;
+    ring3_data->code = 0;
+
+    uint64_t base = (uint64_t) &tss;
+    uint32_t limit = sizeof tss;
+
+    // tss descriptor
+    struct gdt_system_entry *ring3_tss = &gdt.tss;
+    ring3_tss->limit_low = limit;
+    ring3_tss->base_low = base & 0xFFFFFF;
+    ring3_tss->accessed = 1;
+
+    // code bit indicates whether its 32 bit or 16 bit
+    ring3_tss->code = 1;
+    // tss descriptor is ring 0
+    // tss available flag = 0
+    ring3_tss->base_high = (base >> 27) & 0xFF;
+    ring3_tss->limit_low = limit & 0xFFFFFFF;
+    ring3_tss->limit_high = (limit >> 27) & 0xf;
+
+    tss.ist1 = (uint64_t) &ist1_stack[4095];// this one is for traps
+    tss.ist2 = (uint64_t) &ist2_stack[4095];// for double faults
+    tss.rsp0 = (uint64_t) &rsp0_stack[4095];// for kernel stack
+
+    struct {
+        uint16_t limit;
+        uint64_t base;
+    } __attribute__((packed)) gdt_descriptor = { 0 };
+
+    gdt_descriptor.limit = sizeof(gdt) - 1;
+    gdt_descriptor.base = (uint64_t)&gdt;
+
+    // ring 3 time
+    asm volatile(
+            "lgdt %0\n"
+
+            // not too sure if this is allowed for x86_64
+           // "mov ax, $0x23\n"
+           // "mov ds, ax\n"
+           // "mov es, ax\n"
+           // "mov fs, ax\n"
+           // "mov gs, ax\n"
+
+            "mov %%rax, %%rsp\n"// get the stack
+            "push $0x23\n"      // 0x23 | 3 (data selector)
+            "push %%rax\n"      // stack address
+            // pushf is sufficient but just in case
+            "push $0x202\n" // rflag (interrupt enable flag on)
+            "push $0x1B\n"// 0x18 | 3 (code selector)
+            "push %1\n"   // function
+            "iretq\n" ::"m"(gdt), "m"(function_address) );
+}
+
+// osdev said I needed this
+void tss_set_kernel_stack(uint64_t stack) {
+    tss.rsp0 = stack;
+}
\ No newline at end of file
diff --git a/kernel/src/arch/x86_64/usermode/usermode.h b/kernel/src/arch/x86_64/usermode/usermode.h
new file mode 100644
index 0000000..3382bb5
--- /dev/null
+++ b/kernel/src/arch/x86_64/usermode/usermode.h
@@ -0,0 +1,103 @@
+#pragma once
+
+#include <stdint.h>
+
+// Shamelessly stolen from: https://wiki.osdev.org/Getting_to_Ring_3
+struct gdt_entry {
+    // segment limit (limit of the segments size)
+    uint64_t limit_low : 16;
+
+    // base address = virtual address to start of segment
+    uint64_t base_low  : 24;
+
+    uint64_t accessed  : 1;
+    // code is readable
+    // data is writable
+    uint64_t read_write : 1;
+
+    // conforming for code, expand down for data
+	uint64_t conforming_expand_down :  1; 
+    // 1 for code, 0 for data
+	uint64_t code                   :  1; 
+
+    // should be 1 for everything but TSS and LDT
+	uint64_t code_data_segment      :  1;
+
+    // privilege level
+	uint64_t DPL                    :  2; 
+	// indicates that segment referenced by the descriptor is loaded in memory
+    uint64_t present                :  1;
+
+	uint64_t limit_high             :  4;
+
+    // only used in software; has no effect on hardware
+	uint64_t available              :  1;
+    // self explaintory (it enables long mode!!!)
+	uint64_t long_mode              :  1;
+    // 32-bit opcodes for code, uint32_t stack for data
+	uint64_t big                    :  1;
+    // 1 to use 4k page addressing, 0 for byte addressing
+	uint64_t gran                   :  1;
+   
+	uint64_t base_high              :  8;
+
+} __attribute__((packed));
+
+struct gdt_system_entry {
+    uint64_t limit_low : 16;
+    uint64_t base_low : 24;
+    
+    // types
+    uint64_t accessed  : 1;
+    uint64_t read_write : 1;
+	uint64_t conforming_expand_down :  1; 
+    uint64_t code                   :  1; 
+
+    // always 0
+    uint64_t code_data_segment      :  1;
+    
+    uint64_t DPL : 2;
+    uint64_t present : 1;
+    uint64_t limit_high : 4;
+    uint64_t available : 1;
+    uint64_t unused : 2;
+    uint64_t gran : 1;
+
+    uint64_t base_mid : 8;
+    
+    // * end of first 64 bits
+
+    uint64_t base_high : 32;
+    uint64_t reserved_low : 8;
+    uint64_t must_be_zero : 5;
+    uint64_t reerved_high : 19;
+} __attribute__((packed));
+
+// Refer to page 377 (Figure 12-8) in AMD manual
+struct tss_entry {
+    uint32_t reserved_low;
+    uint64_t rsp0;
+    uint64_t rsp1;
+    uint64_t rsp2;
+    uint64_t reserved_mid;
+    uint64_t ist1;
+    uint64_t ist2;
+    uint64_t ist3;
+    uint64_t ist4;
+    uint64_t ist5;
+    uint64_t ist6;
+    uint64_t ist7;
+    uint64_t reserved_high;
+    uint16_t reserved_higher;
+    uint16_t io_base_address;
+} __attribute__((packed));
+
+struct gdt {
+    struct gdt_entry null;
+    struct gdt_entry code;
+    struct gdt_entry data;
+    struct gdt_system_entry tss;
+} __attribute__((packed));
+
+void enter_usermode(void *function_address);
+void tss_set_kernel_stack(uint64_t stack);
\ No newline at end of file
diff --git a/kernel/src/kernel_main.c b/kernel/src/kernel_main.c
index 852db97..defd0df 100644
--- a/kernel/src/kernel_main.c
+++ b/kernel/src/kernel_main.c
@@ -13,6 +13,7 @@
 #include "arch/x86_64/klib/klib.h"
 #include "arch/x86_64/memory/paging.h"
 #include "arch/x86_64/serial/serial.h"
+#include "arch/x86_64/usermode/usermode.h"
 #include "arch/x86_64/vga/vga.h"
 #include "io.h"
 
@@ -29,6 +30,10 @@ void exception_handler(void) {
     _die();
 }
 
+void _Noreturn user_main(void) {
+    while (1) puts("Hello, world!\n");
+}
+
 /*
  * The entry point after the bootloader finishes setting up x86 32-bit protected
  * mode.
@@ -86,7 +91,6 @@ void _Noreturn kernel_main(struct boot_parameters parameters) {
     puts("Successfully loaded idt\n");
 
     char message[] = "X Hello world!\n";
-    unsigned int i = 0;
 
     uint64_t test_virtual_address = (KERNEL_MAPPING_ADDRESS | 0xFFFFFFF);
     map_page(test_virtual_address, 0xFFFFFFF, PAGE_PRESENT);
@@ -102,7 +106,7 @@ void _Noreturn kernel_main(struct boot_parameters parameters) {
 
     puts("Successfully freed virtual address!\n");
 
-    while (1) {
+    for (size_t i = 0; i < 2; i++) {
         message[0] = '0' + i;
         i = (i + 1) % 10;
 
@@ -112,13 +116,14 @@ void _Noreturn kernel_main(struct boot_parameters parameters) {
                get_timer_ticks(), parameters.address_range_count);
 
         vga_set_color(1 + (i % 6), VGA_COLOR_BLACK);
-        memmap_print_entries(parameters.address_range_count,
-                             parameters.address_ranges);
-
+        //memmap_print_entries(parameters.address_range_count,
+        //                     parameters.address_ranges);
+//
         asm volatile("int %0" : : "i"(0x80) : "memory");
 
         ksleep(276447232);
     }
+    enter_usermode((void *) user_main);
 }
 
 static void read_acpi(void) {

From c0720f1c34ff3a1a5a263a5a415d0877988ba53f Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Fri, 17 Jan 2025 18:01:23 +1000
Subject: [PATCH 02/22] Fix gdt (WIP)

---
 CMakeLists.txt                             |  2 +-
 kernel/src/arch/x86_64/usermode/usermode.c | 80 +++++++++++++---------
 kernel/src/arch/x86_64/usermode/usermode.h | 50 +++++++-------
 kernel/src/kernel_main.c                   |  4 +-
 4 files changed, 77 insertions(+), 59 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1487383..42a0756 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -21,4 +21,4 @@ add_custom_command(
 add_custom_target(os ALL DEPENDS "os.img")
 add_dependencies(os bootloader kernel)
 
-add_custom_target(run COMMAND qemu-system-x86_64 -cpu qemu64 -drive file=os.img,format=raw -serial stdio DEPENDS os)
+add_custom_target(run COMMAND qemu-system-x86_64 -cpu qemu64 -drive file=os.img,format=raw -serial stdio -no-reboot -d int -D qemu.log DEPENDS os)
diff --git a/kernel/src/arch/x86_64/usermode/usermode.c b/kernel/src/arch/x86_64/usermode/usermode.c
index 947207f..b6d141f 100644
--- a/kernel/src/arch/x86_64/usermode/usermode.c
+++ b/kernel/src/arch/x86_64/usermode/usermode.c
@@ -1,15 +1,25 @@
 #include "usermode.h"
 
+#include "../../../io.h"
+
 static struct gdt gdt = {0};
+
+struct {
+    uint16_t limit;
+    uint64_t base;
+} __attribute__((packed)) gdt_descriptor = {
+        .limit = sizeof(gdt) - 1,
+        .base = (uint64_t) &gdt};
+
 static struct tss_entry tss = {0};
 
-static uint8_t ist1_stack[4096];
-static uint8_t ist2_stack[4096];
-static uint8_t rsp0_stack[4096];
+static uint8_t ist1_stack[4096] __attribute__((aligned(16)));
+static uint8_t ist2_stack[4096] __attribute__((aligned(16)));
+static uint8_t rsp0_stack[4096] __attribute__((aligned(16)));
 
 void enter_usermode(void *function_address) {
-    struct gdt_entry *ring3_code = &gdt.code;
-    struct gdt_entry *ring3_data = &gdt.data;
+    struct gdt_entry *ring3_code = &gdt.user_code;
+    struct gdt_entry *ring3_data = &gdt.user_data;
 
     // ! EVERYTHING NOT SET IS ZERO !
     ring3_code->limit_low = 0xFFFF;
@@ -29,55 +39,61 @@ void enter_usermode(void *function_address) {
     // data is basically the same besides the code bit
     *ring3_data = *ring3_code;
     ring3_data->code = 0;
+    ring3_data->long_mode = 0;
 
     uint64_t base = (uint64_t) &tss;
-    uint32_t limit = sizeof tss;
+    uint32_t limit = sizeof(tss) - 1;
 
     // tss descriptor
     struct gdt_system_entry *ring3_tss = &gdt.tss;
-    ring3_tss->limit_low = limit;
     ring3_tss->base_low = base & 0xFFFFFF;
+    ring3_tss->limit_low = limit & 0xFFFFFF;
+
     ring3_tss->accessed = 1;
+    ring3_tss->present = 1;
 
     // code bit indicates whether its 32 bit or 16 bit
     ring3_tss->code = 1;
+    
     // tss descriptor is ring 0
     // tss available flag = 0
+    
     ring3_tss->base_high = (base >> 27) & 0xFF;
-    ring3_tss->limit_low = limit & 0xFFFFFFF;
-    ring3_tss->limit_high = (limit >> 27) & 0xf;
+    ring3_tss->limit_high = (limit >> 27) & 0xF;
 
     tss.ist1 = (uint64_t) &ist1_stack[4095];// this one is for traps
     tss.ist2 = (uint64_t) &ist2_stack[4095];// for double faults
     tss.rsp0 = (uint64_t) &rsp0_stack[4095];// for kernel stack
 
-    struct {
-        uint16_t limit;
-        uint64_t base;
-    } __attribute__((packed)) gdt_descriptor = { 0 };
+    // ring 3 time
+    // triple faults here sometimes?
+    asm volatile("lgdt %0\n" ::"m"(gdt_descriptor));
 
-    gdt_descriptor.limit = sizeof(gdt) - 1;
-    gdt_descriptor.base = (uint64_t)&gdt;
+    krintf("GDT LOADED\n");
 
-    // ring 3 time
+    // triple faults here sometimes too?
     asm volatile(
-            "lgdt %0\n"
-
             // not too sure if this is allowed for x86_64
-           // "mov ax, $0x23\n"
-           // "mov ds, ax\n"
-           // "mov es, ax\n"
-           // "mov fs, ax\n"
-           // "mov gs, ax\n"
-
-            "mov %%rax, %%rsp\n"// get the stack
-            "push $0x23\n"      // 0x23 | 3 (data selector)
-            "push %%rax\n"      // stack address
-            // pushf is sufficient but just in case
-            "push $0x202\n" // rflag (interrupt enable flag on)
-            "push $0x1B\n"// 0x18 | 3 (code selector)
-            "push %1\n"   // function
-            "iretq\n" ::"m"(gdt), "m"(function_address) );
+            "mov $0x23, %%ax\n"
+            "mov %%ax, %%ds\n"
+            "mov %%ax, %%es\n"
+            "mov %%ax, %%fs\n"
+            "mov %%ax, %%gs\n" ::);
+
+    krintf("SETUP SEGMENTS %x\n", (uint64_t) function_address);
+
+    // ! triple faults here (General protection fault)
+    asm volatile(
+            "mov %0, %%rax\n"// get the stack
+            "push $0x23\n"   // 0x23 | 3 (user data selector)
+            "push %%rax\n"   // stack address
+            // pushfq is sufficient but just in case
+            "push $0x202\n"// rflag (interrupt enable flag on)
+            "push $0x1B\n" // 0x18 | 3 (user code selector)
+            "push %1\n"    // function
+            "iretq\n" ::
+                    "r"((uint64_t) &rsp0_stack[4095]),
+            "m"(function_address) : "rax");
 }
 
 // osdev said I needed this
diff --git a/kernel/src/arch/x86_64/usermode/usermode.h b/kernel/src/arch/x86_64/usermode/usermode.h
index 3382bb5..2e7954b 100644
--- a/kernel/src/arch/x86_64/usermode/usermode.h
+++ b/kernel/src/arch/x86_64/usermode/usermode.h
@@ -8,54 +8,54 @@ struct gdt_entry {
     uint64_t limit_low : 16;
 
     // base address = virtual address to start of segment
-    uint64_t base_low  : 24;
+    uint64_t base_low : 24;
 
-    uint64_t accessed  : 1;
+    uint64_t accessed : 1;
     // code is readable
     // data is writable
     uint64_t read_write : 1;
 
     // conforming for code, expand down for data
-	uint64_t conforming_expand_down :  1; 
+    uint64_t conforming_expand_down : 1;
     // 1 for code, 0 for data
-	uint64_t code                   :  1; 
+    uint64_t code : 1;
 
     // should be 1 for everything but TSS and LDT
-	uint64_t code_data_segment      :  1;
+    uint64_t code_data_segment : 1;
 
     // privilege level
-	uint64_t DPL                    :  2; 
-	// indicates that segment referenced by the descriptor is loaded in memory
-    uint64_t present                :  1;
+    uint64_t DPL : 2;
+    // indicates that segment referenced by the descriptor is loaded in memory
+    uint64_t present : 1;
 
-	uint64_t limit_high             :  4;
+    uint64_t limit_high : 4;
 
     // only used in software; has no effect on hardware
-	uint64_t available              :  1;
+    uint64_t available : 1;
     // self explaintory (it enables long mode!!!)
-	uint64_t long_mode              :  1;
+    uint64_t long_mode : 1;
     // 32-bit opcodes for code, uint32_t stack for data
-	uint64_t big                    :  1;
+    uint64_t big : 1;
     // 1 to use 4k page addressing, 0 for byte addressing
-	uint64_t gran                   :  1;
-   
-	uint64_t base_high              :  8;
+    uint64_t gran : 1;
+
+    uint64_t base_high : 8;
 
 } __attribute__((packed));
 
 struct gdt_system_entry {
     uint64_t limit_low : 16;
     uint64_t base_low : 24;
-    
+
     // types
-    uint64_t accessed  : 1;
+    uint64_t accessed : 1;
     uint64_t read_write : 1;
-	uint64_t conforming_expand_down :  1; 
-    uint64_t code                   :  1; 
+    uint64_t conforming_expand_down : 1;
+    uint64_t code : 1;
 
     // always 0
-    uint64_t code_data_segment      :  1;
-    
+    uint64_t code_data_segment : 1;
+
     uint64_t DPL : 2;
     uint64_t present : 1;
     uint64_t limit_high : 4;
@@ -64,7 +64,7 @@ struct gdt_system_entry {
     uint64_t gran : 1;
 
     uint64_t base_mid : 8;
-    
+
     // * end of first 64 bits
 
     uint64_t base_high : 32;
@@ -94,8 +94,10 @@ struct tss_entry {
 
 struct gdt {
     struct gdt_entry null;
-    struct gdt_entry code;
-    struct gdt_entry data;
+    struct gdt_entry kernel_code;
+    struct gdt_entry kernel_data;
+    struct gdt_entry user_code;
+    struct gdt_entry user_data;
     struct gdt_system_entry tss;
 } __attribute__((packed));
 
diff --git a/kernel/src/kernel_main.c b/kernel/src/kernel_main.c
index 95bded2..91e521c 100644
--- a/kernel/src/kernel_main.c
+++ b/kernel/src/kernel_main.c
@@ -31,7 +31,7 @@ void exception_handler(void) {
 }
 
 void _Noreturn user_main(void) {
-    while (1) puts("Hello, world!\n");
+    while(1) krintf("sigma balls!\n");
 }
 
 /*
@@ -107,7 +107,7 @@ void _Noreturn kernel_main(struct boot_parameters parameters) {
 
     puts("Successfully freed virtual address!\n");
 
-    for (size_t i = 0; i < 2; i++) {
+    for (size_t i = 0; i < 1; i++) {
         message[0] = '0' + i;
         i = (i + 1) % 10;
 

From 7c3aada3c92b2dfbd67cc1d6ab229ba9cdf66270 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Sat, 18 Jan 2025 13:03:18 +1000
Subject: [PATCH 03/22] Make interrupts executable in gdt (wip)

---
 kernel/src/arch/x86_64/cpu/idt.h           |  8 ---
 kernel/src/arch/x86_64/klib/klib.h         | 42 +++++++++++++++-
 kernel/src/arch/x86_64/klib/trap.c         |  6 +++
 kernel/src/arch/x86_64/usermode/usermode.c | 57 +++++++++++++++++-----
 kernel/src/arch/x86_64/usermode/usermode.h |  4 +-
 kernel/src/kernel_main.c                   | 12 ++---
 6 files changed, 98 insertions(+), 31 deletions(-)

diff --git a/kernel/src/arch/x86_64/cpu/idt.h b/kernel/src/arch/x86_64/cpu/idt.h
index 74db166..bed760e 100644
--- a/kernel/src/arch/x86_64/cpu/idt.h
+++ b/kernel/src/arch/x86_64/cpu/idt.h
@@ -24,14 +24,6 @@ enum gate_type {
     TRAP_64_GATE = 0xF
 };
 
-struct interrupt_frame {
-    uint32_t ip;
-    uint32_t cs;
-    uint32_t flags;
-    uint32_t sp;
-    uint32_t ss;
-};
-
 void setup_interrupt_gate(uint32_t irq, void *base, enum gate_type type, uint8_t privilege_level, uint8_t ist);
 
 void load_idt(void);
diff --git a/kernel/src/arch/x86_64/klib/klib.h b/kernel/src/arch/x86_64/klib/klib.h
index f026923..38a652f 100644
--- a/kernel/src/arch/x86_64/klib/klib.h
+++ b/kernel/src/arch/x86_64/klib/klib.h
@@ -6,7 +6,45 @@
 // Sleep for given ticks
 void ksleep(int ticks);
 
-struct interrupt_frame;
+struct interrupt_frame {
+    // --- 1) General-purpose registers pushed by our assembly stub ---
+    uint64_t r15;
+    uint64_t r14;
+    uint64_t r13;
+    uint64_t r12;
+    uint64_t r11;
+    uint64_t r10;
+    uint64_t r9;
+    uint64_t r8;
+    uint64_t rsi;
+    uint64_t rdi;
+    uint64_t rbp;
+    uint64_t rdx;
+    uint64_t rcx;
+    uint64_t rbx;
+    uint64_t rax;
+
+    // Interrupt/exception number (pushed by the stub)
+    uint64_t int_no;
+
+    // Error code:
+    //  - Automatically pushed by CPU for some exceptions (e.g., page fault),
+    //    or
+    //  - Pushed as 0 by our assembly stub for exceptions that do not push an error code
+    uint64_t err_code;
+
+    // --- 2) IRET frame (pushed automatically by CPU) ---
+    // RIP (instruction pointer) at time of interrupt/exception
+    uint64_t rip;
+    // Code segment selector at time of interrupt/exception
+    uint64_t cs;
+    // Saved RFLAGS
+    uint64_t rflags;
+    // Only pushed by CPU if privilege-level change (e.g., user->kernel)
+    uint64_t rsp;
+    // Only pushed by CPU if privilege-level change
+    uint64_t ss;
+} __attribute__((packed));
 
 // Trap gate
 void trap(struct interrupt_frame *frame);
@@ -17,3 +55,5 @@ void heap_init(void);
 void *kmalloc(size_t size);
 // Frees the memory allocated from heap.
 void free(void *address);
+
+void exception_handler(struct interrupt_frame *frame);
\ No newline at end of file
diff --git a/kernel/src/arch/x86_64/klib/trap.c b/kernel/src/arch/x86_64/klib/trap.c
index fda1d73..4b92f9f 100644
--- a/kernel/src/arch/x86_64/klib/trap.c
+++ b/kernel/src/arch/x86_64/klib/trap.c
@@ -5,3 +5,9 @@
 __attribute__((interrupt)) void trap(struct interrupt_frame *frame) {
     puts("Trap\n");
 }
+
+__attribute__((interrupt)) void exception_handler(struct interrupt_frame *frame) {
+    krintf("Fatal Error Occurred! Error Code: %x\n", frame->err_code);
+    while (1) asm volatile("cli\nhlt" ::);
+}
+
diff --git a/kernel/src/arch/x86_64/usermode/usermode.c b/kernel/src/arch/x86_64/usermode/usermode.c
index b6d141f..5f5d4ae 100644
--- a/kernel/src/arch/x86_64/usermode/usermode.c
+++ b/kernel/src/arch/x86_64/usermode/usermode.c
@@ -2,6 +2,8 @@
 
 #include "../../../io.h"
 
+#include "../memory/paging.h"
+
 static struct gdt gdt = {0};
 
 struct {
@@ -9,7 +11,8 @@ struct {
     uint64_t base;
 } __attribute__((packed)) gdt_descriptor = {
         .limit = sizeof(gdt) - 1,
-        .base = (uint64_t) &gdt};
+        .base = (uint64_t) &gdt
+};
 
 static struct tss_entry tss = {0};
 
@@ -18,7 +21,21 @@ static uint8_t ist2_stack[4096] __attribute__((aligned(16)));
 static uint8_t rsp0_stack[4096] __attribute__((aligned(16)));
 
 void enter_usermode(void *function_address) {
+
+    struct gdt_entry *ring3_kcode = &gdt.kernel_code;
+    struct gdt_entry *ring3_kdata = &gdt.kernel_data;
+    ring3_kcode->read_write = 1;
+    ring3_kcode->code_data_segment = 1;
+    ring3_kcode->present = 1;
+    ring3_kcode->long_mode = 1;
+    ring3_kcode->code = 1;
+
+    *ring3_kdata = *ring3_kcode;
+    ring3_kdata->code = 0;
+    ring3_kdata->long_mode = 0;
+    
     struct gdt_entry *ring3_code = &gdt.user_code;
+    
     struct gdt_entry *ring3_data = &gdt.user_data;
 
     // ! EVERYTHING NOT SET IS ZERO !
@@ -39,10 +56,11 @@ void enter_usermode(void *function_address) {
     // data is basically the same besides the code bit
     *ring3_data = *ring3_code;
     ring3_data->code = 0;
+    // long mode not used as attribute
     ring3_data->long_mode = 0;
 
     uint64_t base = (uint64_t) &tss;
-    uint32_t limit = sizeof(tss) - 1;
+    uint32_t limit = sizeof(tss);
 
     // tss descriptor
     struct gdt_system_entry *ring3_tss = &gdt.tss;
@@ -54,10 +72,10 @@ void enter_usermode(void *function_address) {
 
     // code bit indicates whether its 32 bit or 16 bit
     ring3_tss->code = 1;
-    
+
     // tss descriptor is ring 0
     // tss available flag = 0
-    
+
     ring3_tss->base_high = (base >> 27) & 0xFF;
     ring3_tss->limit_high = (limit >> 27) & 0xF;
 
@@ -65,38 +83,53 @@ void enter_usermode(void *function_address) {
     tss.ist2 = (uint64_t) &ist2_stack[4095];// for double faults
     tss.rsp0 = (uint64_t) &rsp0_stack[4095];// for kernel stack
 
+
     // ring 3 time
     // triple faults here sometimes?
     asm volatile("lgdt %0\n" ::"m"(gdt_descriptor));
 
     krintf("GDT LOADED\n");
 
-    // triple faults here sometimes too?
+    // flush tss
+    asm volatile(
+            "mov $40, %%ax\n"
+            "ltr %%ax" ::: "ax");
+
+    // triple faults here sometimes too? A
     asm volatile(
             // not too sure if this is allowed for x86_64
             "mov $0x23, %%ax\n"
             "mov %%ax, %%ds\n"
             "mov %%ax, %%es\n"
-            "mov %%ax, %%fs\n"
-            "mov %%ax, %%gs\n" ::);
+     //       "mov %%ax, %%fs\n"
+      //      "mov %%ax, %%gs\n" ::);
+      ::);
 
     krintf("SETUP SEGMENTS %x\n", (uint64_t) function_address);
 
     // ! triple faults here (General protection fault)
+    // ! not paged ?
+    uint64_t new = (KERNEL_MAPPING_ADDRESS | (uint64_t)&rsp0_stack[4095]);
+    map_page(new, (uint64_t)&rsp0_stack[4095], PAGE_PRESENT | PAGE_WRITE | PAGE_USER);
+    
+
     asm volatile(
             "mov %0, %%rax\n"// get the stack
-            "push $0x23\n"   // 0x23 | 3 (user data selector)
+            
+            "push $0x23\n"   // 0x20 | 3 (user data selector)
             "push %%rax\n"   // stack address
+            
             // pushfq is sufficient but just in case
             "push $0x202\n"// rflag (interrupt enable flag on)
-            "push $0x1B\n" // 0x18 | 3 (user code selector)
+            
+            "push $0x1b\n" // 0x18 | 3 (user code selector)
             "push %1\n"    // function
             "iretq\n" ::
-                    "r"((uint64_t) &rsp0_stack[4095]),
-            "m"(function_address) : "rax");
+                    "r"((uint64_t) new),
+            "r"((uint64_t)function_address) : "rax");
 }
 
 // osdev said I needed this
 void tss_set_kernel_stack(uint64_t stack) {
     tss.rsp0 = stack;
-}
\ No newline at end of file
+}
diff --git a/kernel/src/arch/x86_64/usermode/usermode.h b/kernel/src/arch/x86_64/usermode/usermode.h
index 2e7954b..cdfe405 100644
--- a/kernel/src/arch/x86_64/usermode/usermode.h
+++ b/kernel/src/arch/x86_64/usermode/usermode.h
@@ -71,7 +71,7 @@ struct gdt_system_entry {
     uint64_t reserved_low : 8;
     uint64_t must_be_zero : 5;
     uint64_t reerved_high : 19;
-} __attribute__((packed));
+} __attribute__((packed)); 
 
 // Refer to page 377 (Figure 12-8) in AMD manual
 struct tss_entry {
@@ -102,4 +102,4 @@ struct gdt {
 } __attribute__((packed));
 
 void enter_usermode(void *function_address);
-void tss_set_kernel_stack(uint64_t stack);
\ No newline at end of file
+void tss_set_kernel_stack(uint64_t stack);
diff --git a/kernel/src/kernel_main.c b/kernel/src/kernel_main.c
index 91e521c..a3c184a 100644
--- a/kernel/src/kernel_main.c
+++ b/kernel/src/kernel_main.c
@@ -24,14 +24,10 @@ void _Noreturn _die(void) {
     while (1) asm volatile("cli\nhlt" ::);
 }
 
-// todo: move this to its own file later
-void exception_handler(void) {
-    puts("Fatal Error Occurred!");
-    _die();
-}
-
 void _Noreturn user_main(void) {
-    while(1) krintf("sigma balls!\n");
+    _die();
+    puts("test\n");
+    while(1);
 }
 
 /*
@@ -124,7 +120,7 @@ void _Noreturn kernel_main(struct boot_parameters parameters) {
 
         ksleep(276447232);
     }
-    enter_usermode((void *) user_main);
+    enter_usermode((void *)user_main);
 }
 
 static void read_acpi(void) {

From c7e88102c55ff8d63c63a2d27f047fc6a63b61e2 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Sat, 18 Jan 2025 21:08:45 +1000
Subject: [PATCH 04/22] Implement user mode (working)

---
 bootloader/src/lm.asm              |  9 ++++---
 kernel/src/arch/x86_64/klib/klib.h | 43 +++++-------------------------
 kernel/src/arch/x86_64/klib/trap.c |  2 +-
 kernel/src/kernel_main.c           |  3 +--
 4 files changed, 13 insertions(+), 44 deletions(-)

diff --git a/bootloader/src/lm.asm b/bootloader/src/lm.asm
index 06dff81..fd6f0a9 100644
--- a/bootloader/src/lm.asm
+++ b/bootloader/src/lm.asm
@@ -2,6 +2,7 @@
 
 PAGE_PRESENT    equ (1 << 0)
 PAGE_WRITE      equ (1 << 1)
+PAGE_USER       equ (1 << 2)
 
 ; check if it collides with anything later on
 paging_table_buffer equ 0x9000
@@ -79,7 +80,7 @@ switch_to_lm:
 
 	; address of page directory pointer table
 	lea	eax, 	[di + 0x1000]
-	or	eax, 	PAGE_PRESENT | PAGE_WRITE
+	or	eax, 	PAGE_PRESENT | PAGE_WRITE | PAGE_USER
 	mov	[di], eax
 
 	; point the page directory pointer table [0]
@@ -87,7 +88,7 @@ switch_to_lm:
 
 	; address of page directory
 	lea	eax, 	[di + 0x2000]
-	or	eax, 	PAGE_PRESENT | PAGE_WRITE
+	or	eax, 	PAGE_PRESENT | PAGE_WRITE | PAGE_USER
 	mov	[di + 0x1000], eax
 
 	; point the page directory [0]
@@ -95,13 +96,13 @@ switch_to_lm:
 
 	; address of page table
 	lea	eax, 	[di + 0x3000]
-	or	eax, 	PAGE_PRESENT | PAGE_WRITE
+	or	eax, 	PAGE_PRESENT | PAGE_WRITE | PAGE_USER
 	mov	[di + 0x2000], eax
 
 	; initialise variables before build
 	push	di
 	lea	di, 	[di + 0x3000]
-	mov	eax, 	PAGE_PRESENT | PAGE_WRITE
+	mov	eax, 	PAGE_PRESENT | PAGE_WRITE | PAGE_USER
 
 	; builds page table
 	; it points each entry to a address
diff --git a/kernel/src/arch/x86_64/klib/klib.h b/kernel/src/arch/x86_64/klib/klib.h
index 38a652f..be4b496 100644
--- a/kernel/src/arch/x86_64/klib/klib.h
+++ b/kernel/src/arch/x86_64/klib/klib.h
@@ -7,43 +7,12 @@
 void ksleep(int ticks);
 
 struct interrupt_frame {
-    // --- 1) General-purpose registers pushed by our assembly stub ---
-    uint64_t r15;
-    uint64_t r14;
-    uint64_t r13;
-    uint64_t r12;
-    uint64_t r11;
-    uint64_t r10;
-    uint64_t r9;
-    uint64_t r8;
-    uint64_t rsi;
-    uint64_t rdi;
-    uint64_t rbp;
-    uint64_t rdx;
-    uint64_t rcx;
-    uint64_t rbx;
-    uint64_t rax;
-
-    // Interrupt/exception number (pushed by the stub)
-    uint64_t int_no;
-
-    // Error code:
-    //  - Automatically pushed by CPU for some exceptions (e.g., page fault),
-    //    or
-    //  - Pushed as 0 by our assembly stub for exceptions that do not push an error code
-    uint64_t err_code;
-
-    // --- 2) IRET frame (pushed automatically by CPU) ---
-    // RIP (instruction pointer) at time of interrupt/exception
-    uint64_t rip;
-    // Code segment selector at time of interrupt/exception
-    uint64_t cs;
-    // Saved RFLAGS
-    uint64_t rflags;
-    // Only pushed by CPU if privilege-level change (e.g., user->kernel)
-    uint64_t rsp;
-    // Only pushed by CPU if privilege-level change
-    uint64_t ss;
+    uint64_t one;
+    uint64_t two;
+    uint64_t three;
+    uint64_t four;
+    uint64_t five;
+    uint64_t six;
 } __attribute__((packed));
 
 // Trap gate
diff --git a/kernel/src/arch/x86_64/klib/trap.c b/kernel/src/arch/x86_64/klib/trap.c
index 4b92f9f..28a4236 100644
--- a/kernel/src/arch/x86_64/klib/trap.c
+++ b/kernel/src/arch/x86_64/klib/trap.c
@@ -7,7 +7,7 @@ __attribute__((interrupt)) void trap(struct interrupt_frame *frame) {
 }
 
 __attribute__((interrupt)) void exception_handler(struct interrupt_frame *frame) {
-    krintf("Fatal Error Occurred! Error Code: %x\n", frame->err_code);
+    krintf("Fatal Error Occurred! Error Code: %x\n", frame->one);
     while (1) asm volatile("cli\nhlt" ::);
 }
 
diff --git a/kernel/src/kernel_main.c b/kernel/src/kernel_main.c
index a3c184a..9cd3494 100644
--- a/kernel/src/kernel_main.c
+++ b/kernel/src/kernel_main.c
@@ -25,8 +25,7 @@ void _Noreturn _die(void) {
 }
 
 void _Noreturn user_main(void) {
-    _die();
-    puts("test\n");
+    //puts("test\n");
     while(1);
 }
 

From c33c2c491215d64a3456da4b188ff8647b394517 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Sat, 18 Jan 2025 21:10:34 +1000
Subject: [PATCH 05/22] Fix style

---
 kernel/src/arch/x86_64/klib/klib.h         |  2 +-
 kernel/src/arch/x86_64/usermode/usermode.c | 12 ++++++------
 kernel/src/arch/x86_64/usermode/usermode.h |  2 +-
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/kernel/src/arch/x86_64/klib/klib.h b/kernel/src/arch/x86_64/klib/klib.h
index be4b496..d9d73a5 100644
--- a/kernel/src/arch/x86_64/klib/klib.h
+++ b/kernel/src/arch/x86_64/klib/klib.h
@@ -25,4 +25,4 @@ void *kmalloc(size_t size);
 // Frees the memory allocated from heap.
 void free(void *address);
 
-void exception_handler(struct interrupt_frame *frame);
\ No newline at end of file
+void exception_handler(struct interrupt_frame *frame);
diff --git a/kernel/src/arch/x86_64/usermode/usermode.c b/kernel/src/arch/x86_64/usermode/usermode.c
index 5f5d4ae..6c7ffdc 100644
--- a/kernel/src/arch/x86_64/usermode/usermode.c
+++ b/kernel/src/arch/x86_64/usermode/usermode.c
@@ -33,9 +33,9 @@ void enter_usermode(void *function_address) {
     *ring3_kdata = *ring3_kcode;
     ring3_kdata->code = 0;
     ring3_kdata->long_mode = 0;
-    
+
     struct gdt_entry *ring3_code = &gdt.user_code;
-    
+
     struct gdt_entry *ring3_data = &gdt.user_data;
 
     // ! EVERYTHING NOT SET IS ZERO !
@@ -111,17 +111,17 @@ void enter_usermode(void *function_address) {
     // ! not paged ?
     uint64_t new = (KERNEL_MAPPING_ADDRESS | (uint64_t)&rsp0_stack[4095]);
     map_page(new, (uint64_t)&rsp0_stack[4095], PAGE_PRESENT | PAGE_WRITE | PAGE_USER);
-    
+
 
     asm volatile(
             "mov %0, %%rax\n"// get the stack
-            
+
             "push $0x23\n"   // 0x20 | 3 (user data selector)
             "push %%rax\n"   // stack address
-            
+
             // pushfq is sufficient but just in case
             "push $0x202\n"// rflag (interrupt enable flag on)
-            
+
             "push $0x1b\n" // 0x18 | 3 (user code selector)
             "push %1\n"    // function
             "iretq\n" ::
diff --git a/kernel/src/arch/x86_64/usermode/usermode.h b/kernel/src/arch/x86_64/usermode/usermode.h
index cdfe405..d9be0d0 100644
--- a/kernel/src/arch/x86_64/usermode/usermode.h
+++ b/kernel/src/arch/x86_64/usermode/usermode.h
@@ -71,7 +71,7 @@ struct gdt_system_entry {
     uint64_t reserved_low : 8;
     uint64_t must_be_zero : 5;
     uint64_t reerved_high : 19;
-} __attribute__((packed)); 
+} __attribute__((packed));
 
 // Refer to page 377 (Figure 12-8) in AMD manual
 struct tss_entry {

From a937819e9c78f5570b0e3b8b9c3b102ec7a4efb6 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Wed, 22 Jan 2025 20:36:14 +1100
Subject: [PATCH 06/22] Fix clang style

---
 kernel/src/arch/x86_64/klib/trap.c         |   1 -
 kernel/src/arch/x86_64/usermode/usermode.c |  27 ++-
 kernel/src/kernel_main.c                   |   6 +-
 llvm.sh                                    | 184 +++++++++++++++++++++
 4 files changed, 197 insertions(+), 21 deletions(-)
 create mode 100644 llvm.sh

diff --git a/kernel/src/arch/x86_64/klib/trap.c b/kernel/src/arch/x86_64/klib/trap.c
index 28a4236..f7fbf1f 100644
--- a/kernel/src/arch/x86_64/klib/trap.c
+++ b/kernel/src/arch/x86_64/klib/trap.c
@@ -10,4 +10,3 @@ __attribute__((interrupt)) void exception_handler(struct interrupt_frame *frame)
     krintf("Fatal Error Occurred! Error Code: %x\n", frame->one);
     while (1) asm volatile("cli\nhlt" ::);
 }
-
diff --git a/kernel/src/arch/x86_64/usermode/usermode.c b/kernel/src/arch/x86_64/usermode/usermode.c
index 6c7ffdc..f28952b 100644
--- a/kernel/src/arch/x86_64/usermode/usermode.c
+++ b/kernel/src/arch/x86_64/usermode/usermode.c
@@ -11,8 +11,7 @@ struct {
     uint64_t base;
 } __attribute__((packed)) gdt_descriptor = {
         .limit = sizeof(gdt) - 1,
-        .base = (uint64_t) &gdt
-};
+        .base = (uint64_t) &gdt};
 
 static struct tss_entry tss = {0};
 
@@ -101,32 +100,26 @@ void enter_usermode(void *function_address) {
             "mov $0x23, %%ax\n"
             "mov %%ax, %%ds\n"
             "mov %%ax, %%es\n"
-     //       "mov %%ax, %%fs\n"
-      //      "mov %%ax, %%gs\n" ::);
-      ::);
+            //       "mov %%ax, %%fs\n"
+            //      "mov %%ax, %%gs\n" ::);
+            ::);
 
     krintf("SETUP SEGMENTS %x\n", (uint64_t) function_address);
 
-    // ! triple faults here (General protection fault)
-    // ! not paged ?
-    uint64_t new = (KERNEL_MAPPING_ADDRESS | (uint64_t)&rsp0_stack[4095]);
-    map_page(new, (uint64_t)&rsp0_stack[4095], PAGE_PRESENT | PAGE_WRITE | PAGE_USER);
-
-
     asm volatile(
             "mov %0, %%rax\n"// get the stack
 
-            "push $0x23\n"   // 0x20 | 3 (user data selector)
-            "push %%rax\n"   // stack address
+            "push $0x23\n"// 0x20 | 3 (user data selector)
+            "push %%rax\n"// stack address
 
             // pushfq is sufficient but just in case
             "push $0x202\n"// rflag (interrupt enable flag on)
 
-            "push $0x1b\n" // 0x18 | 3 (user code selector)
-            "push %1\n"    // function
+            "push $0x1b\n"// 0x18 | 3 (user code selector)
+            "push %1\n"   // function
             "iretq\n" ::
-                    "r"((uint64_t) new),
-            "r"((uint64_t)function_address) : "rax");
+                    "r"((uint64_t) &rsp0_stack[4095]),
+            "r"((uint64_t) function_address) : "rax");
 }
 
 // osdev said I needed this
diff --git a/kernel/src/kernel_main.c b/kernel/src/kernel_main.c
index 9cd3494..9dde68f 100644
--- a/kernel/src/kernel_main.c
+++ b/kernel/src/kernel_main.c
@@ -26,7 +26,7 @@ void _Noreturn _die(void) {
 
 void _Noreturn user_main(void) {
     //puts("test\n");
-    while(1);
+    while (1);
 }
 
 /*
@@ -114,12 +114,12 @@ void _Noreturn kernel_main(struct boot_parameters parameters) {
         vga_set_color(1 + (i % 6), VGA_COLOR_BLACK);
         //memmap_print_entries(parameters.address_range_count,
         //                     parameters.address_ranges);
-//
+        //
         asm volatile("int %0" : : "i"(0x80) : "memory");
 
         ksleep(276447232);
     }
-    enter_usermode((void *)user_main);
+    enter_usermode((void *) user_main);
 }
 
 static void read_acpi(void) {
diff --git a/llvm.sh b/llvm.sh
new file mode 100644
index 0000000..b27ffd5
--- /dev/null
+++ b/llvm.sh
@@ -0,0 +1,184 @@
+#!/bin/bash
+################################################################################
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+################################################################################
+#
+# This script will install the llvm toolchain on the different
+# Debian and Ubuntu versions
+
+set -eux
+
+usage() {
+    set +x
+    echo "Usage: $0 [llvm_major_version] [all] [OPTIONS]" 1>&2
+    echo -e "all\t\t\tInstall all packages." 1>&2
+    echo -e "-n=code_name\t\tSpecifies the distro codename, for example bionic" 1>&2
+    echo -e "-h\t\t\tPrints this help." 1>&2
+    echo -e "-m=repo_base_url\tSpecifies the base URL from which to download." 1>&2
+    exit 1;
+}
+
+CURRENT_LLVM_STABLE=18
+BASE_URL="http://apt.llvm.org"
+
+# Check for required tools
+needed_binaries=(lsb_release wget add-apt-repository gpg)
+missing_binaries=()
+for binary in "${needed_binaries[@]}"; do
+    if ! which $binary &>/dev/null ; then
+        missing_binaries+=($binary)
+    fi
+done
+if [[ ${#missing_binaries[@]} -gt 0 ]] ; then
+    echo "You are missing some tools this script requires: ${missing_binaries[@]}"
+    echo "(hint: apt install lsb-release wget software-properties-common gnupg)"
+    exit 4
+fi
+
+# Set default values for commandline arguments
+# We default to the current stable branch of LLVM
+LLVM_VERSION=$CURRENT_LLVM_STABLE
+ALL=0
+DISTRO=$(lsb_release -is)
+VERSION=$(lsb_release -sr)
+UBUNTU_CODENAME=""
+CODENAME_FROM_ARGUMENTS=""
+# Obtain VERSION_CODENAME and UBUNTU_CODENAME (for Ubuntu and its derivatives)
+source /etc/os-release
+DISTRO=${DISTRO,,}
+case ${DISTRO} in
+    debian)
+        # Debian Trixie has a workaround because of
+        # https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1038383
+        if [[ "${VERSION}" == "unstable" ]] || [[ "${VERSION}" == "testing" ]] || [[ "${VERSION_CODENAME}" == "trixie" ]]; then
+            CODENAME=unstable
+            LINKNAME=
+        else
+            # "stable" Debian release
+            CODENAME=${VERSION_CODENAME}
+            LINKNAME=-${CODENAME}
+        fi
+        ;;
+    *)
+        # ubuntu and its derivatives
+        if [[ -n "${UBUNTU_CODENAME}" ]]; then
+            CODENAME=${UBUNTU_CODENAME}
+            if [[ -n "${CODENAME}" ]]; then
+                LINKNAME=-${CODENAME}
+            fi
+        fi
+        ;;
+esac
+
+# read optional command line arguments
+if [ "$#" -ge 1 ] && [ "${1::1}" != "-" ]; then
+    if [ "$1" != "all" ]; then
+        LLVM_VERSION=$1
+    else
+        # special case for ./llvm.sh all
+        ALL=1
+    fi
+    OPTIND=2
+    if [ "$#" -ge 2 ]; then
+      if [ "$2" == "all" ]; then
+          # Install all packages
+          ALL=1
+          OPTIND=3
+      fi
+    fi
+fi
+
+while getopts ":hm:n:" arg; do
+    case $arg in
+    h)
+        usage
+        ;;
+    m)
+        BASE_URL=${OPTARG}
+        ;;
+    n)
+        CODENAME=${OPTARG}
+        if [[ "${CODENAME}" == "unstable" ]]; then
+            # link name does not apply to unstable repository
+            LINKNAME=
+        else
+            LINKNAME=-${CODENAME}
+        fi
+        CODENAME_FROM_ARGUMENTS="true"
+        ;;
+    esac
+done
+
+if [[ $EUID -ne 0 ]]; then
+   echo "This script must be run as root!"
+   exit 1
+fi
+
+declare -A LLVM_VERSION_PATTERNS
+LLVM_VERSION_PATTERNS[9]="-9"
+LLVM_VERSION_PATTERNS[10]="-10"
+LLVM_VERSION_PATTERNS[11]="-11"
+LLVM_VERSION_PATTERNS[12]="-12"
+LLVM_VERSION_PATTERNS[13]="-13"
+LLVM_VERSION_PATTERNS[14]="-14"
+LLVM_VERSION_PATTERNS[15]="-15"
+LLVM_VERSION_PATTERNS[16]="-16"
+LLVM_VERSION_PATTERNS[17]="-17"
+LLVM_VERSION_PATTERNS[18]="-18"
+LLVM_VERSION_PATTERNS[19]="-19"
+LLVM_VERSION_PATTERNS[20]=""
+
+if [ ! ${LLVM_VERSION_PATTERNS[$LLVM_VERSION]+_} ]; then
+    echo "This script does not support LLVM version $LLVM_VERSION"
+    exit 3
+fi
+
+LLVM_VERSION_STRING=${LLVM_VERSION_PATTERNS[$LLVM_VERSION]}
+
+# join the repository name
+if [[ -n "${CODENAME}" ]]; then
+    REPO_NAME="deb ${BASE_URL}/${CODENAME}/  llvm-toolchain${LINKNAME}${LLVM_VERSION_STRING} main"
+
+    # check if the repository exists for the distro and version
+    if ! wget -q --method=HEAD ${BASE_URL}/${CODENAME} &> /dev/null; then
+        if [[ -n "${CODENAME_FROM_ARGUMENTS}" ]]; then
+            echo "Specified codename '${CODENAME}' is not supported by this script."
+        else
+            echo "Distribution '${DISTRO}' in version '${VERSION}' is not supported by this script."
+        fi
+        exit 2
+    fi
+fi
+
+
+# install everything
+
+if [[ ! -f /etc/apt/trusted.gpg.d/apt.llvm.org.asc ]]; then
+    # download GPG key once
+    wget -qO- https://apt.llvm.org/llvm-snapshot.gpg.key | tee /etc/apt/trusted.gpg.d/apt.llvm.org.asc
+fi
+
+if [[ -z "`apt-key list 2> /dev/null | grep -i llvm`" ]]; then
+    # Delete the key in the old format
+    apt-key del AF4F7421 || true
+fi
+if [[ "${VERSION_CODENAME}" == "bookworm" ]]; then
+    # add it twice to workaround:
+    # https://github.com/llvm/llvm-project/issues/62475
+    add-apt-repository -y "${REPO_NAME}"
+fi
+
+add-apt-repository -y "${REPO_NAME}"
+apt-get update
+PKG="clang-$LLVM_VERSION lldb-$LLVM_VERSION lld-$LLVM_VERSION clangd-$LLVM_VERSION"
+if [[ $ALL -eq 1 ]]; then
+    # same as in test-install.sh
+    # No worries if we have dups
+    PKG="$PKG clang-tidy-$LLVM_VERSION clang-format-$LLVM_VERSION clang-tools-$LLVM_VERSION llvm-$LLVM_VERSION-dev lld-$LLVM_VERSION lldb-$LLVM_VERSION llvm-$LLVM_VERSION-tools libomp-$LLVM_VERSION-dev libc++-$LLVM_VERSION-dev libc++abi-$LLVM_VERSION-dev libclang-common-$LLVM_VERSION-dev libclang-$LLVM_VERSION-dev libclang-cpp$LLVM_VERSION-dev libunwind-$LLVM_VERSION-dev"
+    if test $LLVM_VERSION -gt 14; then
+        PKG="$PKG libclang-rt-$LLVM_VERSION-dev libpolly-$LLVM_VERSION-dev"
+    fi
+fi
+apt-get install -y $PKG

From ac37c2b5c1b26c6071030541279c5489c190bcc5 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Wed, 22 Jan 2025 20:53:50 +1100
Subject: [PATCH 07/22] Remove llvm.sh

---
 llvm.sh | 184 --------------------------------------------------------
 1 file changed, 184 deletions(-)
 delete mode 100644 llvm.sh

diff --git a/llvm.sh b/llvm.sh
deleted file mode 100644
index b27ffd5..0000000
--- a/llvm.sh
+++ /dev/null
@@ -1,184 +0,0 @@
-#!/bin/bash
-################################################################################
-# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-# See https://llvm.org/LICENSE.txt for license information.
-# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-################################################################################
-#
-# This script will install the llvm toolchain on the different
-# Debian and Ubuntu versions
-
-set -eux
-
-usage() {
-    set +x
-    echo "Usage: $0 [llvm_major_version] [all] [OPTIONS]" 1>&2
-    echo -e "all\t\t\tInstall all packages." 1>&2
-    echo -e "-n=code_name\t\tSpecifies the distro codename, for example bionic" 1>&2
-    echo -e "-h\t\t\tPrints this help." 1>&2
-    echo -e "-m=repo_base_url\tSpecifies the base URL from which to download." 1>&2
-    exit 1;
-}
-
-CURRENT_LLVM_STABLE=18
-BASE_URL="http://apt.llvm.org"
-
-# Check for required tools
-needed_binaries=(lsb_release wget add-apt-repository gpg)
-missing_binaries=()
-for binary in "${needed_binaries[@]}"; do
-    if ! which $binary &>/dev/null ; then
-        missing_binaries+=($binary)
-    fi
-done
-if [[ ${#missing_binaries[@]} -gt 0 ]] ; then
-    echo "You are missing some tools this script requires: ${missing_binaries[@]}"
-    echo "(hint: apt install lsb-release wget software-properties-common gnupg)"
-    exit 4
-fi
-
-# Set default values for commandline arguments
-# We default to the current stable branch of LLVM
-LLVM_VERSION=$CURRENT_LLVM_STABLE
-ALL=0
-DISTRO=$(lsb_release -is)
-VERSION=$(lsb_release -sr)
-UBUNTU_CODENAME=""
-CODENAME_FROM_ARGUMENTS=""
-# Obtain VERSION_CODENAME and UBUNTU_CODENAME (for Ubuntu and its derivatives)
-source /etc/os-release
-DISTRO=${DISTRO,,}
-case ${DISTRO} in
-    debian)
-        # Debian Trixie has a workaround because of
-        # https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1038383
-        if [[ "${VERSION}" == "unstable" ]] || [[ "${VERSION}" == "testing" ]] || [[ "${VERSION_CODENAME}" == "trixie" ]]; then
-            CODENAME=unstable
-            LINKNAME=
-        else
-            # "stable" Debian release
-            CODENAME=${VERSION_CODENAME}
-            LINKNAME=-${CODENAME}
-        fi
-        ;;
-    *)
-        # ubuntu and its derivatives
-        if [[ -n "${UBUNTU_CODENAME}" ]]; then
-            CODENAME=${UBUNTU_CODENAME}
-            if [[ -n "${CODENAME}" ]]; then
-                LINKNAME=-${CODENAME}
-            fi
-        fi
-        ;;
-esac
-
-# read optional command line arguments
-if [ "$#" -ge 1 ] && [ "${1::1}" != "-" ]; then
-    if [ "$1" != "all" ]; then
-        LLVM_VERSION=$1
-    else
-        # special case for ./llvm.sh all
-        ALL=1
-    fi
-    OPTIND=2
-    if [ "$#" -ge 2 ]; then
-      if [ "$2" == "all" ]; then
-          # Install all packages
-          ALL=1
-          OPTIND=3
-      fi
-    fi
-fi
-
-while getopts ":hm:n:" arg; do
-    case $arg in
-    h)
-        usage
-        ;;
-    m)
-        BASE_URL=${OPTARG}
-        ;;
-    n)
-        CODENAME=${OPTARG}
-        if [[ "${CODENAME}" == "unstable" ]]; then
-            # link name does not apply to unstable repository
-            LINKNAME=
-        else
-            LINKNAME=-${CODENAME}
-        fi
-        CODENAME_FROM_ARGUMENTS="true"
-        ;;
-    esac
-done
-
-if [[ $EUID -ne 0 ]]; then
-   echo "This script must be run as root!"
-   exit 1
-fi
-
-declare -A LLVM_VERSION_PATTERNS
-LLVM_VERSION_PATTERNS[9]="-9"
-LLVM_VERSION_PATTERNS[10]="-10"
-LLVM_VERSION_PATTERNS[11]="-11"
-LLVM_VERSION_PATTERNS[12]="-12"
-LLVM_VERSION_PATTERNS[13]="-13"
-LLVM_VERSION_PATTERNS[14]="-14"
-LLVM_VERSION_PATTERNS[15]="-15"
-LLVM_VERSION_PATTERNS[16]="-16"
-LLVM_VERSION_PATTERNS[17]="-17"
-LLVM_VERSION_PATTERNS[18]="-18"
-LLVM_VERSION_PATTERNS[19]="-19"
-LLVM_VERSION_PATTERNS[20]=""
-
-if [ ! ${LLVM_VERSION_PATTERNS[$LLVM_VERSION]+_} ]; then
-    echo "This script does not support LLVM version $LLVM_VERSION"
-    exit 3
-fi
-
-LLVM_VERSION_STRING=${LLVM_VERSION_PATTERNS[$LLVM_VERSION]}
-
-# join the repository name
-if [[ -n "${CODENAME}" ]]; then
-    REPO_NAME="deb ${BASE_URL}/${CODENAME}/  llvm-toolchain${LINKNAME}${LLVM_VERSION_STRING} main"
-
-    # check if the repository exists for the distro and version
-    if ! wget -q --method=HEAD ${BASE_URL}/${CODENAME} &> /dev/null; then
-        if [[ -n "${CODENAME_FROM_ARGUMENTS}" ]]; then
-            echo "Specified codename '${CODENAME}' is not supported by this script."
-        else
-            echo "Distribution '${DISTRO}' in version '${VERSION}' is not supported by this script."
-        fi
-        exit 2
-    fi
-fi
-
-
-# install everything
-
-if [[ ! -f /etc/apt/trusted.gpg.d/apt.llvm.org.asc ]]; then
-    # download GPG key once
-    wget -qO- https://apt.llvm.org/llvm-snapshot.gpg.key | tee /etc/apt/trusted.gpg.d/apt.llvm.org.asc
-fi
-
-if [[ -z "`apt-key list 2> /dev/null | grep -i llvm`" ]]; then
-    # Delete the key in the old format
-    apt-key del AF4F7421 || true
-fi
-if [[ "${VERSION_CODENAME}" == "bookworm" ]]; then
-    # add it twice to workaround:
-    # https://github.com/llvm/llvm-project/issues/62475
-    add-apt-repository -y "${REPO_NAME}"
-fi
-
-add-apt-repository -y "${REPO_NAME}"
-apt-get update
-PKG="clang-$LLVM_VERSION lldb-$LLVM_VERSION lld-$LLVM_VERSION clangd-$LLVM_VERSION"
-if [[ $ALL -eq 1 ]]; then
-    # same as in test-install.sh
-    # No worries if we have dups
-    PKG="$PKG clang-tidy-$LLVM_VERSION clang-format-$LLVM_VERSION clang-tools-$LLVM_VERSION llvm-$LLVM_VERSION-dev lld-$LLVM_VERSION lldb-$LLVM_VERSION llvm-$LLVM_VERSION-tools libomp-$LLVM_VERSION-dev libc++-$LLVM_VERSION-dev libc++abi-$LLVM_VERSION-dev libclang-common-$LLVM_VERSION-dev libclang-$LLVM_VERSION-dev libclang-cpp$LLVM_VERSION-dev libunwind-$LLVM_VERSION-dev"
-    if test $LLVM_VERSION -gt 14; then
-        PKG="$PKG libclang-rt-$LLVM_VERSION-dev libpolly-$LLVM_VERSION-dev"
-    fi
-fi
-apt-get install -y $PKG

From c5d8f74ef56727e3332fbd568b4eca6efa813dc6 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Sun, 26 Jan 2025 11:28:26 +1100
Subject: [PATCH 08/22] Use higher free memory region

---
 CMakeLists.txt       | 2 +-
 kernel/src/kernel.ld | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3633fb5..60277c1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -10,7 +10,7 @@ add_custom_command(
         COMMAND ${CMAKE_CURRENT_SOURCE_DIR}/tools/bind_kernel.py
                 --bootloader "bootloader/boot.bin"
                 --kernel $<TARGET_FILE:kernel>
-                --entry 0x2000
+                --entry 0xD000
                 --output "os.img"
         DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/tools/bind_kernel.py
                 "bootloader/boot.bin"
diff --git a/kernel/src/kernel.ld b/kernel/src/kernel.ld
index c7a41c6..268f119 100644
--- a/kernel/src/kernel.ld
+++ b/kernel/src/kernel.ld
@@ -7,7 +7,7 @@ SECTIONS {
     /* Define the memory layout and where sections are placed */
 
     /* Place the code starting at 0x2000 */
-    . = 0x2000; /* Set the starting address for code */
+    . = 0xD000; /* Set the starting address for code */
 
     /* kmain must be absolutely first */
     .text.kernel_main : {

From aeaa7848a3a8e7fcf5208c34259d20e90c5b1823 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Sun, 26 Jan 2025 20:47:20 +1100
Subject: [PATCH 09/22] Add documentation and usermode test

---
 kernel/CMakeLists.txt                         |  1 +
 kernel/src/arch/x86_64/tests/usermode_tests.c | 16 ++++++++++++++++
 kernel/src/arch/x86_64/usermode/usermode.c    |  6 +-----
 kernel/src/arch/x86_64/usermode/usermode.h    |  2 +-
 4 files changed, 19 insertions(+), 6 deletions(-)
 create mode 100644 kernel/src/arch/x86_64/tests/usermode_tests.c

diff --git a/kernel/CMakeLists.txt b/kernel/CMakeLists.txt
index 8915fd6..f6f9246 100644
--- a/kernel/CMakeLists.txt
+++ b/kernel/CMakeLists.txt
@@ -27,6 +27,7 @@ if(KAOLIN_ENABLE_TESTS)
             src/arch/x86_64/tests/test.c
             src/arch/x86_64/tests/memory_tests.c
             src/tests/heap_tests.c
+            src/arch/x86_64/tests/usermode_tests.c
     )
 endif()
 
diff --git a/kernel/src/arch/x86_64/tests/usermode_tests.c b/kernel/src/arch/x86_64/tests/usermode_tests.c
new file mode 100644
index 0000000..afe18c6
--- /dev/null
+++ b/kernel/src/arch/x86_64/tests/usermode_tests.c
@@ -0,0 +1,16 @@
+#include "../../../io.h"
+#include "../../../test.h"
+#include "../usermode/usermode.h"
+#include "../serial/serial.h"
+
+// ! THIS NEEDS TO BE THE LAST TEST !
+static void usermode_function(void) {
+    outw(0xf4, 0x10);
+    while(1);
+}
+
+static void usermode_test(void) {
+    enter_usermode(usermode_function);
+}
+
+TEST("Enter usermode", usermode_test)
diff --git a/kernel/src/arch/x86_64/usermode/usermode.c b/kernel/src/arch/x86_64/usermode/usermode.c
index f28952b..2186499 100644
--- a/kernel/src/arch/x86_64/usermode/usermode.c
+++ b/kernel/src/arch/x86_64/usermode/usermode.c
@@ -120,9 +120,5 @@ void enter_usermode(void *function_address) {
             "iretq\n" ::
                     "r"((uint64_t) &rsp0_stack[4095]),
             "r"((uint64_t) function_address) : "rax");
-}
-
-// osdev said I needed this
-void tss_set_kernel_stack(uint64_t stack) {
-    tss.rsp0 = stack;
+    puts("foo\n");
 }
diff --git a/kernel/src/arch/x86_64/usermode/usermode.h b/kernel/src/arch/x86_64/usermode/usermode.h
index d9be0d0..6124024 100644
--- a/kernel/src/arch/x86_64/usermode/usermode.h
+++ b/kernel/src/arch/x86_64/usermode/usermode.h
@@ -101,5 +101,5 @@ struct gdt {
     struct gdt_system_entry tss;
 } __attribute__((packed));
 
+// Enters usermode
 void enter_usermode(void *function_address);
-void tss_set_kernel_stack(uint64_t stack);

From e33d366f6098dc4c4366467e8c5d0e82a9e98f79 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Mon, 27 Jan 2025 14:16:40 +1100
Subject: [PATCH 10/22] Implement print for software interrupt

---
 kernel/CMakeLists.txt                         |  3 +-
 kernel/src/arch/x86_64/klib/klib.c            |  6 ++++
 kernel/src/arch/x86_64/klib/klib.h            |  3 ++
 kernel/src/arch/x86_64/klib/trap.c            | 33 ++++++++++++++++++-
 kernel/src/arch/x86_64/tests/usermode_tests.c |  9 ++++-
 kernel/src/arch/x86_64/usermode/usermode.c    | 11 +------
 kernel/src/kernel_main.c                      | 22 +------------
 7 files changed, 53 insertions(+), 34 deletions(-)

diff --git a/kernel/CMakeLists.txt b/kernel/CMakeLists.txt
index f6f9246..1dbdd2d 100644
--- a/kernel/CMakeLists.txt
+++ b/kernel/CMakeLists.txt
@@ -1,4 +1,5 @@
-option(KAOLIN_ENABLE_TESTS "Enable tests" OFF)
+unset(KAOLIN_ENABLE_TESTS CACHE)
+option(KAOLIN_ENABLE_TESTS "Enable tests" ON)
 
 set(LINKER_SCRIPT "${CMAKE_CURRENT_SOURCE_DIR}/src/kernel.ld")
 
diff --git a/kernel/src/arch/x86_64/klib/klib.c b/kernel/src/arch/x86_64/klib/klib.c
index 47c184b..d144e9a 100644
--- a/kernel/src/arch/x86_64/klib/klib.c
+++ b/kernel/src/arch/x86_64/klib/klib.c
@@ -6,3 +6,9 @@ void ksleep(int ticks) {
     init_apic_timer(ticks, 0x20);
     while (get_apic_timer_current());
 }
+
+_Noreturn void _die(void) {
+    while (1) {
+        asm volatile("cli\nhlt" ::);
+    }
+}
diff --git a/kernel/src/arch/x86_64/klib/klib.h b/kernel/src/arch/x86_64/klib/klib.h
index d9d73a5..ac0a27d 100644
--- a/kernel/src/arch/x86_64/klib/klib.h
+++ b/kernel/src/arch/x86_64/klib/klib.h
@@ -26,3 +26,6 @@ void *kmalloc(size_t size);
 void free(void *address);
 
 void exception_handler(struct interrupt_frame *frame);
+
+// Stops the kernel
+void _die(void);
diff --git a/kernel/src/arch/x86_64/klib/trap.c b/kernel/src/arch/x86_64/klib/trap.c
index f7fbf1f..9b40d82 100644
--- a/kernel/src/arch/x86_64/klib/trap.c
+++ b/kernel/src/arch/x86_64/klib/trap.c
@@ -3,7 +3,38 @@
 #include "../../../io.h"
 
 __attribute__((interrupt)) void trap(struct interrupt_frame *frame) {
-    puts("Trap\n");
+    // rax is the system call number
+    // args are in rdi, rsi, rdx
+
+    uint64_t system_call;
+    uint64_t arg_1;
+    uint64_t arg_2;
+    uint64_t arg_3;
+
+    asm volatile("mov %%rax, %0\n"
+                 "mov %%rdi, %1\n"
+                 "mov %%rsi, %2\n"
+                 "mov %%rdx, %3\n"
+                 : "=r"(system_call), "=r"(arg_1), "=r"(arg_2), "=r"(arg_3)
+                 :);
+
+    switch (system_call) {
+        case 0:
+            puts((const char *) arg_1);
+            break;
+        case 1:
+            putc((char) (arg_1 & 0xFF));
+            break;
+        case 2:
+            puti((int) (arg_1 & 0xFFFFFFFF));
+            break;
+        default:
+            // todo: return a sentinel value to indicate invalids
+            puts("Invalid system call!\n");
+    }
+
+
+    //puts("Trap\n");
 }
 
 __attribute__((interrupt)) void exception_handler(struct interrupt_frame *frame) {
diff --git a/kernel/src/arch/x86_64/tests/usermode_tests.c b/kernel/src/arch/x86_64/tests/usermode_tests.c
index afe18c6..83d6355 100644
--- a/kernel/src/arch/x86_64/tests/usermode_tests.c
+++ b/kernel/src/arch/x86_64/tests/usermode_tests.c
@@ -1,10 +1,17 @@
 #include "../../../io.h"
 #include "../../../test.h"
-#include "../usermode/usermode.h"
 #include "../serial/serial.h"
+#include "../usermode/usermode.h"
 
 // ! THIS NEEDS TO BE THE LAST TEST !
 static void usermode_function(void) {
+    char *finish = "Usermode test successful\n";
+
+    asm volatile(
+            "mov %0, %%rax\n"
+            "mov %1, %%rdi\n"
+            "int %2"
+            : : "r"((unsigned long) 0), "r"(finish), "i"(0x80) : "memory");
     outw(0xf4, 0x10);
     while(1);
 }
diff --git a/kernel/src/arch/x86_64/usermode/usermode.c b/kernel/src/arch/x86_64/usermode/usermode.c
index 2186499..9a8c9b2 100644
--- a/kernel/src/arch/x86_64/usermode/usermode.c
+++ b/kernel/src/arch/x86_64/usermode/usermode.c
@@ -1,7 +1,5 @@
 #include "usermode.h"
 
-#include "../../../io.h"
-
 #include "../memory/paging.h"
 
 static struct gdt gdt = {0};
@@ -84,17 +82,13 @@ void enter_usermode(void *function_address) {
 
 
     // ring 3 time
-    // triple faults here sometimes?
     asm volatile("lgdt %0\n" ::"m"(gdt_descriptor));
 
-    krintf("GDT LOADED\n");
-
     // flush tss
     asm volatile(
             "mov $40, %%ax\n"
             "ltr %%ax" ::: "ax");
 
-    // triple faults here sometimes too? A
     asm volatile(
             // not too sure if this is allowed for x86_64
             "mov $0x23, %%ax\n"
@@ -103,9 +97,7 @@ void enter_usermode(void *function_address) {
             //       "mov %%ax, %%fs\n"
             //      "mov %%ax, %%gs\n" ::);
             ::);
-
-    krintf("SETUP SEGMENTS %x\n", (uint64_t) function_address);
-
+    
     asm volatile(
             "mov %0, %%rax\n"// get the stack
 
@@ -120,5 +112,4 @@ void enter_usermode(void *function_address) {
             "iretq\n" ::
                     "r"((uint64_t) &rsp0_stack[4095]),
             "r"((uint64_t) function_address) : "rax");
-    puts("foo\n");
 }
diff --git a/kernel/src/kernel_main.c b/kernel/src/kernel_main.c
index 8f69415..b2cc0cd 100644
--- a/kernel/src/kernel_main.c
+++ b/kernel/src/kernel_main.c
@@ -28,12 +28,6 @@ static void read_acpi(void);
 
 static void setup_idt(void);
 
-_Noreturn static void _die(void) {
-    while (1) {
-        asm volatile("cli\nhlt" ::);
-    }
-}
-
 void _Noreturn user_main(void) {
     //puts("test\n");
     while (1);
@@ -99,20 +93,6 @@ void _Noreturn kernel_main(struct boot_parameters parameters) {
 #else
     char message[] = "X Hello world!\n";
 
-    uint64_t test_virtual_address = (KERNEL_MAPPING_ADDRESS | 0xFFFFFFF);
-    map_page(test_virtual_address, 0xFFFFFFF, PAGE_PRESENT);
-    if (!verify_mapping(test_virtual_address)) {
-        puts("Could not page correctly!\n");
-        _die();
-    }
-    free_address(test_virtual_address);
-    if (verify_mapping(test_virtual_address)) {
-        puts("Could not free virtual address correctly!\n");
-        _die();
-    }
-
-    puts("Successfully freed virtual address!\n");
-
     for (size_t i = 0; i < 1; i++) {
         message[0] = '0' + i;
         i = (i + 1) % 10;
@@ -207,7 +187,7 @@ static void setup_idt(void) {
     // we have interrupt after 31 since 0-31 are reserved for errors
     setup_interrupt_gate(0x20, timer_handler, INTERRUPT_64_GATE, 0, 0);
     setup_interrupt_gate(0x21, keyboard_handler, INTERRUPT_64_GATE, 0, 0);
-    setup_interrupt_gate(0x80, trap, TRAP_64_GATE, 0, 0);
+    setup_interrupt_gate(0x80, trap, TRAP_64_GATE, 3, 0);
 
     load_idt();
 }

From 91f04518e431a298ac234b7093980c0ab3addc58 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Mon, 27 Jan 2025 14:40:53 +1100
Subject: [PATCH 11/22] Fix merge conflict from rebase

---
 kernel/CMakeLists.txt | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/CMakeLists.txt b/kernel/CMakeLists.txt
index 1dbdd2d..f6f9246 100644
--- a/kernel/CMakeLists.txt
+++ b/kernel/CMakeLists.txt
@@ -1,5 +1,4 @@
-unset(KAOLIN_ENABLE_TESTS CACHE)
-option(KAOLIN_ENABLE_TESTS "Enable tests" ON)
+option(KAOLIN_ENABLE_TESTS "Enable tests" OFF)
 
 set(LINKER_SCRIPT "${CMAKE_CURRENT_SOURCE_DIR}/src/kernel.ld")
 

From a9634a16320c5116ad1d4d5959a1f2553dcda2c9 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Mon, 27 Jan 2025 14:24:58 +1100
Subject: [PATCH 12/22] Fix style

---
 kernel/src/arch/x86_64/tests/usermode_tests.c | 2 +-
 kernel/src/arch/x86_64/usermode/usermode.c    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/src/arch/x86_64/tests/usermode_tests.c b/kernel/src/arch/x86_64/tests/usermode_tests.c
index 83d6355..7df2ba9 100644
--- a/kernel/src/arch/x86_64/tests/usermode_tests.c
+++ b/kernel/src/arch/x86_64/tests/usermode_tests.c
@@ -13,7 +13,7 @@ static void usermode_function(void) {
             "int %2"
             : : "r"((unsigned long) 0), "r"(finish), "i"(0x80) : "memory");
     outw(0xf4, 0x10);
-    while(1);
+    while (1);
 }
 
 static void usermode_test(void) {
diff --git a/kernel/src/arch/x86_64/usermode/usermode.c b/kernel/src/arch/x86_64/usermode/usermode.c
index 9a8c9b2..1d24b95 100644
--- a/kernel/src/arch/x86_64/usermode/usermode.c
+++ b/kernel/src/arch/x86_64/usermode/usermode.c
@@ -97,7 +97,7 @@ void enter_usermode(void *function_address) {
             //       "mov %%ax, %%fs\n"
             //      "mov %%ax, %%gs\n" ::);
             ::);
-    
+
     asm volatile(
             "mov %0, %%rax\n"// get the stack
 

From ca053f9cef35ef85cf3fb32e6fe85e6a264d1b77 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Mon, 27 Jan 2025 14:35:07 +1100
Subject: [PATCH 13/22] Fix offset and add msg to user_main

---
 bootloader/src/stage0.asm | 10 +++++-----
 kernel/src/kernel_main.c  |  8 ++++++--
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/bootloader/src/stage0.asm b/bootloader/src/stage0.asm
index 8764b49..083c78d 100644
--- a/bootloader/src/stage0.asm
+++ b/bootloader/src/stage0.asm
@@ -19,18 +19,18 @@
 	call	disk_load_lba
 
 	; temporarily load kernel image metadata
-	; 0x2000..0x2004 : uintptr_t entry
-	; 0x2000..0x2006 : uint16_t sectors
-	mov	dword	[dap_dest], 0x2000
+	; 0xD000..0xD004 : uintptr_t entry
+	; 0xD000..0xD006 : uint16_t sectors
+	mov	dword	[dap_dest], 0xD000
 	mov	word	[dap_sectors], 1
 	mov	dword	[dap_lba], 0x2
 	call	disk_load_lba
 
-	mov	eax,	dword [0x2000]
+	mov	eax,	dword [0xD000]
 	mov	dword	[dap_dest], eax
 	mov	dword	[kernel_entry], eax
 
-	mov	ax,	word [0x2004]
+	mov	ax,	word [0xD004]
 	mov	word	[dap_sectors], ax
 
 	; load actual kernel image
diff --git a/kernel/src/kernel_main.c b/kernel/src/kernel_main.c
index b2cc0cd..eb62512 100644
--- a/kernel/src/kernel_main.c
+++ b/kernel/src/kernel_main.c
@@ -29,7 +29,12 @@ static void read_acpi(void);
 static void setup_idt(void);
 
 void _Noreturn user_main(void) {
-    //puts("test\n");
+    const char *msg = "Entered usermode!\n";
+        asm volatile(
+            "mov %0, %%rax\n"
+            "mov %1, %%rdi\n"
+            "int %2"
+            : : "r"((unsigned long) 0), "r"(msg), "i"(0x80) : "memory");
     while (1);
 }
 
@@ -106,7 +111,6 @@ void _Noreturn kernel_main(struct boot_parameters parameters) {
         //memmap_print_entries(parameters.address_range_count,
         //                     parameters.address_ranges);
         //
-        asm volatile("int %0" : : "i"(0x80) : "memory");
 
         ksleep(276447232);
     }

From f6cb35f24f1c703d4aced10193d9d7468bf83629 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Mon, 27 Jan 2025 14:36:29 +1100
Subject: [PATCH 14/22] Fix style

---
 kernel/src/kernel_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/src/kernel_main.c b/kernel/src/kernel_main.c
index eb62512..29b8d54 100644
--- a/kernel/src/kernel_main.c
+++ b/kernel/src/kernel_main.c
@@ -30,7 +30,7 @@ static void setup_idt(void);
 
 void _Noreturn user_main(void) {
     const char *msg = "Entered usermode!\n";
-        asm volatile(
+    asm volatile(
             "mov %0, %%rax\n"
             "mov %1, %%rdi\n"
             "int %2"

From 6d215b10634d00d9e720079a627a7726f761b608 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Wed, 29 Jan 2025 11:15:13 +1100
Subject: [PATCH 15/22] Fix style

---
 kernel/src/arch/x86_64/apic/lapic.c        |  2 +-
 kernel/src/arch/x86_64/klib/klib.h         |  7 +++---
 kernel/src/arch/x86_64/klib/trap.c         | 21 +++++++++--------
 kernel/src/arch/x86_64/usermode/usermode.c | 27 +++++++++++-----------
 4 files changed, 31 insertions(+), 26 deletions(-)

diff --git a/kernel/src/arch/x86_64/apic/lapic.c b/kernel/src/arch/x86_64/apic/lapic.c
index 3e6e66b..0e0f780 100644
--- a/kernel/src/arch/x86_64/apic/lapic.c
+++ b/kernel/src/arch/x86_64/apic/lapic.c
@@ -24,7 +24,7 @@ int apic_get_id(void) {
 static void cpu_set_apic_base(uintptr_t apic) {
     uint32_t edx = 0;
     // osdev says 0xfffff0000 but thats 36 bits - might be a typo?
-    uint32_t eax = (apic & 0xFFFFFF000) | IA32_APIC_BASE_MSR_ENABLE;
+    uint32_t eax = (apic & 0xFFFFF000) | IA32_APIC_BASE_MSR_ENABLE;
 
     cpu_set_msr(IA32_APIC_BASE_MSR, eax, edx);
 }
diff --git a/kernel/src/arch/x86_64/klib/klib.h b/kernel/src/arch/x86_64/klib/klib.h
index ac0a27d..8298fc6 100644
--- a/kernel/src/arch/x86_64/klib/klib.h
+++ b/kernel/src/arch/x86_64/klib/klib.h
@@ -16,7 +16,7 @@ struct interrupt_frame {
 } __attribute__((packed));
 
 // Trap gate
-void trap(struct interrupt_frame *frame);
+__attribute__((interrupt)) void trap(struct interrupt_frame *frame);
 
 // Initialises the heap by mapping it in virtual memory.
 void heap_init(void);
@@ -25,7 +25,8 @@ void *kmalloc(size_t size);
 // Frees the memory allocated from heap.
 void free(void *address);
 
-void exception_handler(struct interrupt_frame *frame);
+// Exception Handler
+__attribute__((interrupt)) void exception_handler(struct interrupt_frame *frame);
 
 // Stops the kernel
-void _die(void);
+_Noreturn void _die(void);
diff --git a/kernel/src/arch/x86_64/klib/trap.c b/kernel/src/arch/x86_64/klib/trap.c
index 9b40d82..6940f2c 100644
--- a/kernel/src/arch/x86_64/klib/trap.c
+++ b/kernel/src/arch/x86_64/klib/trap.c
@@ -2,7 +2,7 @@
 
 #include "../../../io.h"
 
-__attribute__((interrupt)) void trap(struct interrupt_frame *frame) {
+void trap(struct interrupt_frame *frame) {
     // rax is the system call number
     // args are in rdi, rsi, rdx
 
@@ -29,15 +29,18 @@ __attribute__((interrupt)) void trap(struct interrupt_frame *frame) {
             puti((int) (arg_1 & 0xFFFFFFFF));
             break;
         default:
-            // todo: return a sentinel value to indicate invalids
-            puts("Invalid system call!\n");
+            asm volatile("mov $0, %%rax\n" : : "r"((uint64_t) -1));
     }
-
-
-    //puts("Trap\n");
 }
 
-__attribute__((interrupt)) void exception_handler(struct interrupt_frame *frame) {
-    krintf("Fatal Error Occurred! Error Code: %x\n", frame->one);
-    while (1) asm volatile("cli\nhlt" ::);
+void exception_handler(struct interrupt_frame *frame) {
+    puts("Exception Occurred!\n");
+    krintf("Error Code/RIP: %x\n", frame->six);
+    krintf("RIP/CS:         %x\n", frame->five);
+    krintf("CS/RFLAGS:      %x\n", frame->four);
+    krintf("RFLAGS/RSP:     %x\n", frame->three);
+    krintf("RSP/SS:         %x\n", frame->two);
+    krintf("SS:             %x\n", frame->one);
+
+    _die();
 }
diff --git a/kernel/src/arch/x86_64/usermode/usermode.c b/kernel/src/arch/x86_64/usermode/usermode.c
index 1d24b95..97eae7f 100644
--- a/kernel/src/arch/x86_64/usermode/usermode.c
+++ b/kernel/src/arch/x86_64/usermode/usermode.c
@@ -13,9 +13,11 @@ struct {
 
 static struct tss_entry tss = {0};
 
-static uint8_t ist1_stack[4096] __attribute__((aligned(16)));
-static uint8_t ist2_stack[4096] __attribute__((aligned(16)));
-static uint8_t rsp0_stack[4096] __attribute__((aligned(16)));
+#define STACK_SIZE 4096
+
+static uint8_t ist1_stack[STACK_SIZE] __attribute__((aligned(16)));
+static uint8_t ist2_stack[STACK_SIZE] __attribute__((aligned(16)));
+static uint8_t rsp0_stack[STACK_SIZE] __attribute__((aligned(16)));
 
 void enter_usermode(void *function_address) {
 
@@ -76,9 +78,9 @@ void enter_usermode(void *function_address) {
     ring3_tss->base_high = (base >> 27) & 0xFF;
     ring3_tss->limit_high = (limit >> 27) & 0xF;
 
-    tss.ist1 = (uint64_t) &ist1_stack[4095];// this one is for traps
-    tss.ist2 = (uint64_t) &ist2_stack[4095];// for double faults
-    tss.rsp0 = (uint64_t) &rsp0_stack[4095];// for kernel stack
+    tss.ist1 = (uint64_t) &ist1_stack[STACK_SIZE - 1];// this one is for traps
+    tss.ist2 = (uint64_t) &ist2_stack[STACK_SIZE - 1];// for double faults
+    tss.rsp0 = (uint64_t) &rsp0_stack[STACK_SIZE - 1];// for kernel stack
 
 
     // ring 3 time
@@ -93,10 +95,7 @@ void enter_usermode(void *function_address) {
             // not too sure if this is allowed for x86_64
             "mov $0x23, %%ax\n"
             "mov %%ax, %%ds\n"
-            "mov %%ax, %%es\n"
-            //       "mov %%ax, %%fs\n"
-            //      "mov %%ax, %%gs\n" ::);
-            ::);
+            "mov %%ax, %%es\n" ::);
 
     asm volatile(
             "mov %0, %%rax\n"// get the stack
@@ -109,7 +108,9 @@ void enter_usermode(void *function_address) {
 
             "push $0x1b\n"// 0x18 | 3 (user code selector)
             "push %1\n"   // function
-            "iretq\n" ::
-                    "r"((uint64_t) &rsp0_stack[4095]),
-            "r"((uint64_t) function_address) : "rax");
+            "iretq\n" ::"r"((uint64_t) &rsp0_stack[STACK_SIZE - 1]),
+            "r"((uint64_t) function_address)
+            : "rax");
+
+    __builtin_unreachable();
 }

From c3f73cbb6fb0fd8c05daae634b0b405d5caddb96 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Wed, 29 Jan 2025 11:23:22 +1100
Subject: [PATCH 16/22] Small change

---
 kernel/src/arch/x86_64/klib/klib.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/src/arch/x86_64/klib/klib.h b/kernel/src/arch/x86_64/klib/klib.h
index 8298fc6..8948644 100644
--- a/kernel/src/arch/x86_64/klib/klib.h
+++ b/kernel/src/arch/x86_64/klib/klib.h
@@ -29,4 +29,4 @@ void free(void *address);
 __attribute__((interrupt)) void exception_handler(struct interrupt_frame *frame);
 
 // Stops the kernel
-_Noreturn void _die(void);
+void _Noreturn _die(void);

From b4026c40bc73e97a591f815f7374a33a0fbf116d Mon Sep 17 00:00:00 2001
From: Ramid Khan <ramidzkh@gmail.com>
Date: Wed, 29 Jan 2025 12:49:35 +1100
Subject: [PATCH 17/22] Update kernel/src/arch/x86_64/usermode/usermode.c

---
 kernel/src/arch/x86_64/usermode/usermode.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/src/arch/x86_64/usermode/usermode.c b/kernel/src/arch/x86_64/usermode/usermode.c
index 97eae7f..e66633f 100644
--- a/kernel/src/arch/x86_64/usermode/usermode.c
+++ b/kernel/src/arch/x86_64/usermode/usermode.c
@@ -9,7 +9,8 @@ struct {
     uint64_t base;
 } __attribute__((packed)) gdt_descriptor = {
         .limit = sizeof(gdt) - 1,
-        .base = (uint64_t) &gdt};
+        .base = (uint64_t) &gdt,
+};
 
 static struct tss_entry tss = {0};
 

From 0806b5e170ce0749a45b3310be643cd5bfff61ca Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Wed, 29 Jan 2025 18:56:25 +1100
Subject: [PATCH 18/22] Implement keyboard driver

---
 .../arch/x86_64/drivers/keyboard/keyboard.c   | 142 +++++++++++++++++-
 .../arch/x86_64/drivers/keyboard/keyboard.h   |  10 +-
 kernel/src/arch/x86_64/usermode/usermode.h    |   2 +-
 kernel/src/arch/x86_64/vga/vga.c              |  53 +++++++
 kernel/src/arch/x86_64/vga/vga.h              |   9 ++
 kernel/src/kernel_main.c                      |  18 ++-
 6 files changed, 224 insertions(+), 10 deletions(-)

diff --git a/kernel/src/arch/x86_64/drivers/keyboard/keyboard.c b/kernel/src/arch/x86_64/drivers/keyboard/keyboard.c
index abbc827..10e2435 100644
--- a/kernel/src/arch/x86_64/drivers/keyboard/keyboard.c
+++ b/kernel/src/arch/x86_64/drivers/keyboard/keyboard.c
@@ -2,12 +2,148 @@
 
 #include "../../../../io.h"
 #include "../../apic/lapic.h"
+#include "../../apic/ioapic.h"
+#include "../../cpu/idt.h"
 #include "../../serial/serial.h"
 
-__attribute__((interrupt)) void keyboard_handler(struct interrupt_frame *frame) {
+#include <stdbool.h>
+
+// clang-format off
+enum scan_set_one {
+    // todo: abbreviate names
+    S1_ESC = 1, S1_1, S1_2, S1_3, S1_4,
+    S1_5, S1_6, S1_7, S1_8, S1_9,
+    S1_0, S1_MINUS, S1_EQUAL, S1_BACKSPACE, S1_TAB,
+    S1_Q, S1_W, S1_E, S1_R, S1_T,
+    S1_Y, S1_U, S1_I, S1_O, S1_P, S1_LEFT_BRACKET,
+    S1_RIGHT_BRACKET, S1_ENTER, S1_LEFT_CTRL, S1_A, S1_S,
+    S1_D, S1_F, S1_G, S1_H, S1_J,
+    S1_K, S1_L, S1_SEMI, S1_SINGLE_QUOTE, S1_BACK_TICK,
+    S1_LEFT_SHIFT, S1_LEFT_SLASH, S1_Z, S1_X, S1_C,
+    S1_V, S1_B, S1_N, S1_M, S1_COMMA,
+    S1_DOT, S1_RIGHT_SLASH, S1_RIGHT_SHIFT, S1_KEYPAD_STAR,
+    S1_LEFT_ALT, S1_SPACE, S1_CAPSLOCK, S1_F1, S1_F2,
+    S1_F3, S1_F4, S1_F5, S1_F6, S1_F7,
+    S1_F8, S1_F9, S1_F10, S1_NUMLOCK, S1_SCROLLLOCK,
+    S1_KEYPAD_7, S1_KEYPAD_8, S1_KEYPAD_9, S1_KEYPAD_MINUS,
+    S1_KEYPAD_4, S1_KEYPAD_5, S1_KEYPAD_6, S1_KEYPAD_PLUS,
+    S1_KEYPAD_1, S1_KEYPAD_2, S1_KEYPAD_3, S1_KEYPAD_0,
+    S1_KEYPAD_DOT, S1_F11, S1_F12,
+    // RELEASED
+    // todo: make a map for each key held down
+    S1_ESC_RELEASED = 0x81,
+    S1_1_RELEASED, S1_2_RELEASED, S1_3_RELEASED, S1_4_RELEASED,
+    S1_5_RELEASED, S1_6_RELEASED, S1_7_RELEASED, S1_8_RELEASED,
+    S1_9_RELEASED, S1_0_RELEASED, S1_MINUS_RELEASED, S1_EQUALS_RELEASED,
+    S1_BACKSPACE_RELEASED, S1_TAB_RELEASED, S1_Q_RELEASED, S1_W_RELEASED,
+    S1_E_RELEASED, S1_R_RELEASED, S1_T_RELEASED, S1_Y_RELEASED, S1_U_RELEASED,
+    S1_I_RELEASED, S1_O_RELEASED, S1_P_RELEASED, S1_LEFT_BRACKET_RELEASED,
+    S1_RIGHT_BRACKET_RELEASED, S1_ENTER_RELEASED, S1_LEFT_CTRL_RELEASED, S1_A_RELEASED,
+    S1_S_RELEASED, S1_D_RELEASED, S1_F_RELEASED, S1_G_RELEASED, S1_H_RELEASED,
+    S1_J_RELEASED, S1_K_RELEASED, S1_L_RELEASED, S1_SEMI_RELEASED, S1_SINGLE_QUOTE_RELEASED,
+    S1_BACK_TICK_RELEASED, S1_LEFT_SHIFT_RELEASED, S1_LEFT_SLASH_RELEASED, S1_Z_RELEASED,
+    S1_X_RELEASED, S1_C_RELEASED, S1_V_RELEASED, S1_B_RELEASED, S1_N_RELEASED,
+    S1_M_RELEASED, S1_COMMA_RELEASED, S1_DOT_RELEASED, S1_RIGHT_SLASH_RELEASED,
+    S1_RIGHT_SHIFT_RELEASED, S1_KEYPAD_STAR_RELEASED, S1_LEFT_ALT_RELEASED, S1_SPACE_RELEASED,
+    S1_CAPSLOCK_RELEASED, S1_F1_RELEASED, S1_F2_RELEASED, S1_F3_RELEASED, S1_F4_RELEASED,
+    S1_F5_RELEASED, S1_F6_RELEASED, S1_F7_RELEASED, S1_F8_RELEASED, S1_F9_RELEASED,
+    S1_F10_RELEASED, S1_NUMLOCK_RELEASED, S1_SCROLLLOCK_RELEASED, S1_KEYPAD_7_RELEASED,
+    S1_KEYPAD_8_RELEASED, S1_KEYPAD_9_RELEASED, S1_KEYPAD_MINUS_RELEASED,
+    S1_KEYPAD_4_RELEASED, S1_KEYPAD_5_RELEASED, S1_KEYPAD_6_RELEASED, S1_KEYPAD_PLUS_RELEASED,
+    S1_KEYPAD_1_RELEASED, S1_KEYPAD_2_RELEASED, S1_KEYPAD_3_RELEASED, S1_KEYPAD_0_RELEASED,
+    S1_KEYPAD_DOT_RELEASED, S1_F11_RELEASED, S1_F12_RELEASED
+};
+// clang-format on
+
+#define MAX_BUFFER_SIZE 512
+static char buffer[MAX_BUFFER_SIZE];
+static size_t buffer_pos = 0;
+
+static __attribute__((interrupt)) void keyboard_handler(struct interrupt_frame *frame);
+
+static uint8_t keyboard_code_set_1(const uint8_t data);
+
+static bool caps_lock = 0;
+
+// TODO: use acpi to check if 8042 ps/2 controller is supported
+// todo: poll for keyboard status
+// todo: check keyboard type (1, 2, 3)
+// todo: detect if key is capital or nah (need to detect caps lock and shift)
+
+void keyboard_init(void) {
+    // Disable any devices connected to ps/2 ports
+    //outb(0x64, 0xAD);
+    //outb(0x64, 0xA7);
+    // todo: do the steps specified by osdev later
+
+    int apic_id = apic_get_id();
+    ioapic_set_redirect((uintptr_t *) IOAPIC_VIRTUAL_ADDRESS, 1, 0x21, apic_id);
+    setup_interrupt_gate(0x21, keyboard_handler, INTERRUPT_64_GATE, 0, 0);
+}
+
+// Keycodes from: https://wiki.osdev.org/PS/2_Keyboard
+// CODE SET  1
+// ! for some reason 2,3,4 in qemu r different keys
+static uint8_t keyboard_code_set_1(const uint8_t data) {
+    if (data >= S1_1 && data <= S1_EQUAL) {
+        return "1234567890-="[data - S1_1];
+    } else if (data >= S1_Q && data <= S1_ENTER) {
+        return "QWERTYUIOP[]\n"[data - S1_Q];
+    } else if (data >= S1_A && data <= S1_BACK_TICK) {
+        return "ASDFGHJKL;'`"[data - S1_A];
+    } else if (data >= S1_LEFT_SLASH && data <= S1_RIGHT_SLASH) {
+        return "\\ZXCVBNM,./"[data - S1_LEFT_SLASH];
+    } else if (data >= S1_KEYPAD_7 && data <= S1_KEYPAD_DOT) {
+        return "789-456+1230."[data - S1_KEYPAD_7];
+    } else if (data == S1_SPACE) {
+        return ' ';
+    } else if (data == S1_KEYPAD_STAR) {
+        return '*';
+    } else if (data == S1_CAPSLOCK) {
+        caps_lock = !caps_lock;
+        // enable caps lock LED
+        if (caps_lock) {
+            outb(0xED, inb(0xED) | (1 << 2));
+        } else {
+            outb(0xED, inb(0xED) & ~(1 << 2));
+        }
+    }
+
+    return data;
+}
+
+// TODO: have switch for different code sets
+static char keyboard_convert_code(char data) {
+    return keyboard_code_set_1(data);
+}
+
+// ! figure out how to make it pause/wait for getchar();
+
+// todo: WRITE A FRONTEND FUNCTION FOR KLIB
+char getc(void) {
+    while (buffer_pos == 0) {
+        __builtin_ia32_pause();
+    }
+    char data = buffer[--buffer_pos];
+    putc(data);
+    return data;
+}
+
+void getstr(char *str, size_t len) {
+    for (size_t i = 0; i < len; i++) {
+        str[i] = getc();
+    }
+}
+
+static void keyboard_handler(struct interrupt_frame *frame) {
     // Consume a key, not doing this will only let
     // the interrupt trigger once
-    inb(0x60);
-    puts("Keyboard pressed");
+    uint8_t data = keyboard_code_set_1(inb(0x60));
+    if (data >= 'A' && data <= 'Z' && !caps_lock) data += 32;
+    if (data >= ' ' && data <= '~') buffer[buffer_pos++] = data;
+    // ! minor bug: could loop over and getc wont be able to get the prev 512 chars
+    buffer_pos %= MAX_BUFFER_SIZE;
+    //if (data >= ' ' && data <= '~')
+    //    krintf("Keyboard pressed %c\n", data);
     send_apic_eoi();
 }
diff --git a/kernel/src/arch/x86_64/drivers/keyboard/keyboard.h b/kernel/src/arch/x86_64/drivers/keyboard/keyboard.h
index 2f0e0a6..b3e0334 100644
--- a/kernel/src/arch/x86_64/drivers/keyboard/keyboard.h
+++ b/kernel/src/arch/x86_64/drivers/keyboard/keyboard.h
@@ -1,6 +1,12 @@
 #pragma once
 
+#include <stddef.h>
+
 struct interrupt_frame;
 
-// Keyboard Handler
-void keyboard_handler(struct interrupt_frame *frame);
+// Initialise the keyboard driver
+void keyboard_init(void);
+
+char getc(void);
+
+void getstr(char *str, size_t len);
diff --git a/kernel/src/arch/x86_64/usermode/usermode.h b/kernel/src/arch/x86_64/usermode/usermode.h
index 6124024..ee0fc24 100644
--- a/kernel/src/arch/x86_64/usermode/usermode.h
+++ b/kernel/src/arch/x86_64/usermode/usermode.h
@@ -102,4 +102,4 @@ struct gdt {
 } __attribute__((packed));
 
 // Enters usermode
-void enter_usermode(void *function_address);
+void _Noreturn enter_usermode(void *function_address);
diff --git a/kernel/src/arch/x86_64/vga/vga.c b/kernel/src/arch/x86_64/vga/vga.c
index fc15c3a..88da778 100644
--- a/kernel/src/arch/x86_64/vga/vga.c
+++ b/kernel/src/arch/x86_64/vga/vga.c
@@ -1,5 +1,7 @@
 #include "vga.h"
 
+#include "../serial/serial.h"
+
 #include <stddef.h>
 #include <stdint.h>
 
@@ -91,6 +93,7 @@ void vga_putchar(char c) {
             break;
         }
     }
+    vga_cursor_update(terminal_column, terminal_row);
 }
 
 void vga_write_string(const char *data) {
@@ -98,3 +101,53 @@ void vga_write_string(const char *data) {
         vga_putchar(*data++);
     }
 }
+
+// Found names here: http://www.osdever.net/FreeVGA/vga/crtcreg.htm
+#define CURSOR_ADDRESS_REGISTER 0x3D4
+#define CURSOR_INDEX_REGISTER 0x3D5
+
+// Cursor address
+#define CURSOR_START 0x0A
+#define CURSOR_END 0x0B
+
+#define CURSOR_LOCATION_HIGH 0x0E
+#define CURSOR_LOCATION_LOW 0x0F
+
+void vga_cursor_enable(size_t start, size_t end) {
+    // Writes to CURSOR_ADDRESS_REGISTER first
+    // to specify address
+
+    // start determines start of cursor height
+    // end determines end of cursor height
+    
+    outb(CURSOR_ADDRESS_REGISTER, CURSOR_START);
+    // retain bits 6 and 7 because they are reserved.
+    outb(CURSOR_INDEX_REGISTER, inb(CURSOR_INDEX_REGISTER) & 0xC0 | (uint8_t) (start & 0x3F));
+
+    outb(CURSOR_ADDRESS_REGISTER, CURSOR_END);
+    // retain bits 5, 6, 7 because they are reserved.
+    outb(CURSOR_INDEX_REGISTER, inb(CURSOR_INDEX_REGISTER) & 0xE0 | (uint8_t) (end & 0x1f));
+}
+
+void vga_cursor_disable(void) {
+    outb(CURSOR_ADDRESS_REGISTER, CURSOR_START);
+    // set 5th bit to 1 to disable
+    outb(CURSOR_INDEX_REGISTER, inb(CURSOR_INDEX_REGISTER) & 0xC0 | 0x20);
+}
+
+void vga_cursor_update(size_t x, size_t y) {
+    // todo: ensure 8 bits
+    uint16_t pos = y * VGA_WIDTH + x;
+    outb(CURSOR_ADDRESS_REGISTER, CURSOR_LOCATION_LOW);
+    outb(CURSOR_INDEX_REGISTER, (uint8_t) (pos & 0xFF));
+    outb(CURSOR_ADDRESS_REGISTER, CURSOR_LOCATION_HIGH);
+    outb(CURSOR_INDEX_REGISTER, (uint8_t) ((pos >> 8) & 0xFF));
+}
+
+uint16_t vga_cursor_position(void) {
+    uint16_t pos = 0;
+    outb(CURSOR_ADDRESS_REGISTER, CURSOR_LOCATION_LOW);
+    pos |= inb(CURSOR_INDEX_REGISTER);
+    outb(CURSOR_ADDRESS_REGISTER, CURSOR_LOCATION_HIGH);
+    pos |= inb(CURSOR_INDEX_REGISTER);
+}
diff --git a/kernel/src/arch/x86_64/vga/vga.h b/kernel/src/arch/x86_64/vga/vga.h
index ff7a2d0..9d6d231 100644
--- a/kernel/src/arch/x86_64/vga/vga.h
+++ b/kernel/src/arch/x86_64/vga/vga.h
@@ -36,3 +36,12 @@ void vga_putchar(char c);
 
 // Prints a null-terminated string
 void vga_write_string(const char *data);
+
+// Enables text cursor
+void vga_cursor_enable(size_t start, size_t end);
+
+// Disables text cursor
+void vga_cursor_disable(void);
+
+// Updates text cursor
+void vga_cursor_update(size_t x, size_t y);
diff --git a/kernel/src/kernel_main.c b/kernel/src/kernel_main.c
index 29b8d54..c3626e5 100644
--- a/kernel/src/kernel_main.c
+++ b/kernel/src/kernel_main.c
@@ -96,9 +96,21 @@ void _Noreturn kernel_main(struct boot_parameters parameters) {
     outw(0xf4, 0x10);
     _die();
 #else
+    puts("Enter a character: ");
+    char c = getc();
+    krintf("Char: %c\n", c);
+
+    puts("Enter a string: ");
+    char *str = kmalloc(10);
+    getstr(str, 9);
+    str[9] = '\0';
+    krintf("String: %s\n", str);
+    free(str);
+    
+    
     char message[] = "X Hello world!\n";
 
-    for (size_t i = 0; i < 1; i++) {
+    for (size_t i = 0; i < 5; i++) {
         message[0] = '0' + i;
         i = (i + 1) % 10;
 
@@ -180,8 +192,6 @@ static void setup_idt(void) {
 
     // system timer
     ioapic_set_redirect((uintptr_t *) IOAPIC_VIRTUAL_ADDRESS, 0, 0x20, apic_id);
-    // keyboard
-    ioapic_set_redirect((uintptr_t *) IOAPIC_VIRTUAL_ADDRESS, 1, 0x21, apic_id);
 
     for (size_t vector = 0; vector < 32; vector++) {
         setup_interrupt_gate(vector, exception_handler, INTERRUPT_64_GATE, 0,
@@ -190,7 +200,7 @@ static void setup_idt(void) {
 
     // we have interrupt after 31 since 0-31 are reserved for errors
     setup_interrupt_gate(0x20, timer_handler, INTERRUPT_64_GATE, 0, 0);
-    setup_interrupt_gate(0x21, keyboard_handler, INTERRUPT_64_GATE, 0, 0);
+    keyboard_init();
     setup_interrupt_gate(0x80, trap, TRAP_64_GATE, 3, 0);
 
     load_idt();

From fff51d273765344b745f8de33cce13a97817df80 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Wed, 29 Jan 2025 21:01:01 +1100
Subject: [PATCH 19/22] Implement backspace and shift

---
 .../arch/x86_64/drivers/keyboard/keyboard.c   | 63 ++++++++++++++++---
 .../arch/x86_64/drivers/keyboard/keyboard.h   |  2 +-
 kernel/src/arch/x86_64/usermode/usermode.h    |  4 --
 kernel/src/arch/x86_64/vga/vga.c              | 20 ++++--
 kernel/src/kernel_main.c                      |  7 +--
 5 files changed, 75 insertions(+), 21 deletions(-)

diff --git a/kernel/src/arch/x86_64/drivers/keyboard/keyboard.c b/kernel/src/arch/x86_64/drivers/keyboard/keyboard.c
index 10e2435..e734ca9 100644
--- a/kernel/src/arch/x86_64/drivers/keyboard/keyboard.c
+++ b/kernel/src/arch/x86_64/drivers/keyboard/keyboard.c
@@ -1,8 +1,8 @@
 #include "keyboard.h"
 
 #include "../../../../io.h"
-#include "../../apic/lapic.h"
 #include "../../apic/ioapic.h"
+#include "../../apic/lapic.h"
 #include "../../cpu/idt.h"
 #include "../../serial/serial.h"
 
@@ -62,8 +62,10 @@ static size_t buffer_pos = 0;
 static __attribute__((interrupt)) void keyboard_handler(struct interrupt_frame *frame);
 
 static uint8_t keyboard_code_set_1(const uint8_t data);
+static uint8_t keyboard_shift_conversion(uint8_t data);
 
-static bool caps_lock = 0;
+static bool caps_lock = false;
+static bool shift_pressed = false;
 
 // TODO: use acpi to check if 8042 ps/2 controller is supported
 // todo: poll for keyboard status
@@ -85,8 +87,8 @@ void keyboard_init(void) {
 // CODE SET  1
 // ! for some reason 2,3,4 in qemu r different keys
 static uint8_t keyboard_code_set_1(const uint8_t data) {
-    if (data >= S1_1 && data <= S1_EQUAL) {
-        return "1234567890-="[data - S1_1];
+    if (data >= S1_1 && data <= S1_BACKSPACE) {
+        return "1234567890-=\b"[data - S1_1];
     } else if (data >= S1_Q && data <= S1_ENTER) {
         return "QWERTYUIOP[]\n"[data - S1_Q];
     } else if (data >= S1_A && data <= S1_BACK_TICK) {
@@ -107,6 +109,10 @@ static uint8_t keyboard_code_set_1(const uint8_t data) {
         } else {
             outb(0xED, inb(0xED) & ~(1 << 2));
         }
+    } else if (data == S1_LEFT_SHIFT || data == S1_RIGHT_SHIFT) {
+        shift_pressed = true;
+    } else if (data == S1_LEFT_SHIFT_RELEASED || data == S1_RIGHT_SHIFT_RELEASED) {
+        shift_pressed = false;
     }
 
     return data;
@@ -129,9 +135,49 @@ char getc(void) {
     return data;
 }
 
-void getstr(char *str, size_t len) {
-    for (size_t i = 0; i < len; i++) {
-        str[i] = getc();
+size_t getstr(char *str, size_t len) {
+    size_t i = 0;
+    while (i < len) {
+        char data = getc();
+        if (data == '\n') return i;
+        if (data == '\b') {
+            i--;
+            continue;
+        }
+        str[i] = data;
+        i++;
+    }
+    return i;
+}
+
+static uint8_t keyboard_shift_conversion(uint8_t data) {
+    if (!shift_pressed) return data;
+
+    // Inverse because of caps lock
+    if (data >= 'A' && data <= 'Z') return data + 32;
+    if (data >= 'a' && data <= 'z') return data - 32;
+
+    if (data >= '0' && data <= '9') return ")!@#$%^&*("[data - '0'];
+
+    switch (data) {
+        case '[':
+            return '{';
+        case ']':
+            return '}';
+        case '-':
+            return '_';
+        case '=':
+            return '+';
+        case '\\':
+            return '|';
+        case ';':
+            return ':';
+        case ',':
+            return '<';
+        case '.':
+            return '>';
+        default:
+            return data;
     }
 }
 
@@ -140,7 +186,8 @@ static void keyboard_handler(struct interrupt_frame *frame) {
     // the interrupt trigger once
     uint8_t data = keyboard_code_set_1(inb(0x60));
     if (data >= 'A' && data <= 'Z' && !caps_lock) data += 32;
-    if (data >= ' ' && data <= '~') buffer[buffer_pos++] = data;
+    data = keyboard_shift_conversion(data);
+    if ((data >= ' ' && data <= '~') || data == '\b' || data == '\t') buffer[buffer_pos++] = data;
     // ! minor bug: could loop over and getc wont be able to get the prev 512 chars
     buffer_pos %= MAX_BUFFER_SIZE;
     //if (data >= ' ' && data <= '~')
diff --git a/kernel/src/arch/x86_64/drivers/keyboard/keyboard.h b/kernel/src/arch/x86_64/drivers/keyboard/keyboard.h
index b3e0334..374f6fc 100644
--- a/kernel/src/arch/x86_64/drivers/keyboard/keyboard.h
+++ b/kernel/src/arch/x86_64/drivers/keyboard/keyboard.h
@@ -9,4 +9,4 @@ void keyboard_init(void);
 
 char getc(void);
 
-void getstr(char *str, size_t len);
+size_t getstr(char *str, size_t len);
diff --git a/kernel/src/arch/x86_64/usermode/usermode.h b/kernel/src/arch/x86_64/usermode/usermode.h
index 5d22b67..ee0fc24 100644
--- a/kernel/src/arch/x86_64/usermode/usermode.h
+++ b/kernel/src/arch/x86_64/usermode/usermode.h
@@ -102,8 +102,4 @@ struct gdt {
 } __attribute__((packed));
 
 // Enters usermode
-<<<<<<< HEAD
 void _Noreturn enter_usermode(void *function_address);
-=======
-void enter_usermode(void *function_address);
->>>>>>> fbda0e9466d73581987f2fd6a5025a7e75b383c7
diff --git a/kernel/src/arch/x86_64/vga/vga.c b/kernel/src/arch/x86_64/vga/vga.c
index 88da778..fe0e741 100644
--- a/kernel/src/arch/x86_64/vga/vga.c
+++ b/kernel/src/arch/x86_64/vga/vga.c
@@ -76,6 +76,18 @@ void vga_putchar(char c) {
             terminal_row = 0;
             break;
         }
+        case '\b': {
+            if (terminal_row == 0 && terminal_column == 0) return;
+
+            terminal_column--;
+            if (terminal_column < 0) {
+                terminal_column = VGA_WIDTH - 1;
+                terminal_row--;
+            }
+
+            terminal_putentryat('\0', terminal_color, terminal_column, terminal_row);
+            break;
+        }
         case 0x20 ... 0x7E: {
             terminal_putentryat(c, terminal_color, terminal_column, terminal_row);
 
@@ -104,14 +116,14 @@ void vga_write_string(const char *data) {
 
 // Found names here: http://www.osdever.net/FreeVGA/vga/crtcreg.htm
 #define CURSOR_ADDRESS_REGISTER 0x3D4
-#define CURSOR_INDEX_REGISTER 0x3D5
+#define CURSOR_INDEX_REGISTER   0x3D5
 
 // Cursor address
 #define CURSOR_START 0x0A
-#define CURSOR_END 0x0B
+#define CURSOR_END   0x0B
 
 #define CURSOR_LOCATION_HIGH 0x0E
-#define CURSOR_LOCATION_LOW 0x0F
+#define CURSOR_LOCATION_LOW  0x0F
 
 void vga_cursor_enable(size_t start, size_t end) {
     // Writes to CURSOR_ADDRESS_REGISTER first
@@ -119,7 +131,7 @@ void vga_cursor_enable(size_t start, size_t end) {
 
     // start determines start of cursor height
     // end determines end of cursor height
-    
+
     outb(CURSOR_ADDRESS_REGISTER, CURSOR_START);
     // retain bits 6 and 7 because they are reserved.
     outb(CURSOR_INDEX_REGISTER, inb(CURSOR_INDEX_REGISTER) & 0xC0 | (uint8_t) (start & 0x3F));
diff --git a/kernel/src/kernel_main.c b/kernel/src/kernel_main.c
index c3626e5..d022440 100644
--- a/kernel/src/kernel_main.c
+++ b/kernel/src/kernel_main.c
@@ -102,12 +102,11 @@ void _Noreturn kernel_main(struct boot_parameters parameters) {
 
     puts("Enter a string: ");
     char *str = kmalloc(10);
-    getstr(str, 9);
-    str[9] = '\0';
+    str[getstr(str, 9)] = '\0';
     krintf("String: %s\n", str);
     free(str);
-    
-    
+
+
     char message[] = "X Hello world!\n";
 
     for (size_t i = 0; i < 5; i++) {

From a767235dafe3308c6252b9da7bb8e4bbde792964 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Wed, 29 Jan 2025 21:17:25 +1100
Subject: [PATCH 20/22] Fix caps lock led

---
 .../src/arch/x86_64/drivers/keyboard/keyboard.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/kernel/src/arch/x86_64/drivers/keyboard/keyboard.c b/kernel/src/arch/x86_64/drivers/keyboard/keyboard.c
index e734ca9..e2d9fab 100644
--- a/kernel/src/arch/x86_64/drivers/keyboard/keyboard.c
+++ b/kernel/src/arch/x86_64/drivers/keyboard/keyboard.c
@@ -4,10 +4,17 @@
 #include "../../apic/ioapic.h"
 #include "../../apic/lapic.h"
 #include "../../cpu/idt.h"
+#include "../../klib/klib.h"
 #include "../../serial/serial.h"
 
 #include <stdbool.h>
 
+#define DATA_PORT        0x60
+#define STATUS_REGISTER  0x64
+#define COMMAND_REGISTER STATUS_REGISTER
+
+#define SET_LEDS 0xED
+
 // clang-format off
 enum scan_set_one {
     // todo: abbreviate names
@@ -105,9 +112,13 @@ static uint8_t keyboard_code_set_1(const uint8_t data) {
         caps_lock = !caps_lock;
         // enable caps lock LED
         if (caps_lock) {
-            outb(0xED, inb(0xED) | (1 << 2));
+            outb(DATA_PORT, SET_LEDS);
+            ksleep(5);
+            outb(DATA_PORT, 1 << 2);
         } else {
-            outb(0xED, inb(0xED) & ~(1 << 2));
+            outb(DATA_PORT, SET_LEDS);
+            ksleep(5);
+            outb(DATA_PORT, 0x0);
         }
     } else if (data == S1_LEFT_SHIFT || data == S1_RIGHT_SHIFT) {
         shift_pressed = true;
@@ -184,7 +195,7 @@ static uint8_t keyboard_shift_conversion(uint8_t data) {
 static void keyboard_handler(struct interrupt_frame *frame) {
     // Consume a key, not doing this will only let
     // the interrupt trigger once
-    uint8_t data = keyboard_code_set_1(inb(0x60));
+    uint8_t data = keyboard_code_set_1(inb(DATA_PORT));
     if (data >= 'A' && data <= 'Z' && !caps_lock) data += 32;
     data = keyboard_shift_conversion(data);
     if ((data >= ' ' && data <= '~') || data == '\b' || data == '\t') buffer[buffer_pos++] = data;

From b03c9578519497c5a6bdaa3177b8d6c94da91f61 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Sat, 1 Feb 2025 02:39:59 +1100
Subject: [PATCH 21/22] Add mouse driver

---
 kernel/CMakeLists.txt                         |   1 +
 kernel/src/arch/x86_64/cpu/idt.c              |   4 +-
 kernel/src/arch/x86_64/cpu/idt.h              |   2 +-
 .../arch/x86_64/drivers/keyboard/keyboard.c   |   9 +-
 kernel/src/arch/x86_64/drivers/mouse/mouse.c  | 122 ++++++++++++++++++
 kernel/src/arch/x86_64/drivers/mouse/mouse.h  |   3 +
 kernel/src/kernel_main.c                      |   3 +
 7 files changed, 136 insertions(+), 8 deletions(-)
 create mode 100644 kernel/src/arch/x86_64/drivers/mouse/mouse.c
 create mode 100644 kernel/src/arch/x86_64/drivers/mouse/mouse.h

diff --git a/kernel/CMakeLists.txt b/kernel/CMakeLists.txt
index 7e54f4b..c2e2cab 100644
--- a/kernel/CMakeLists.txt
+++ b/kernel/CMakeLists.txt
@@ -14,6 +14,7 @@ set(COMPILE_OPTIONS
 
 add_library(drivers OBJECT
         src/arch/x86_64/drivers/keyboard/keyboard.c
+        src/arch/x86_64/drivers/mouse/mouse.c
         src/arch/x86_64/drivers/timer/timer.c
         src/arch/x86_64/klib/trap.c
 )
diff --git a/kernel/src/arch/x86_64/cpu/idt.c b/kernel/src/arch/x86_64/cpu/idt.c
index cc93867..3c6abc2 100644
--- a/kernel/src/arch/x86_64/cpu/idt.c
+++ b/kernel/src/arch/x86_64/cpu/idt.c
@@ -15,8 +15,8 @@ static uint16_t idt_segment_descriptor(uint16_t index) {
     return ((index & 0xFFF) << 3);
 }
 
-void setup_interrupt_gate(uint32_t irq, void *base, enum gate_type type, uint8_t privilege_level, uint8_t ist) {
-    struct interrupt_descriptor *interrupt_descriptor = &interrupt_descriptors[irq];
+void setup_interrupt_gate(uint32_t vector, void *base, enum gate_type type, uint8_t privilege_level, uint8_t ist) {
+    struct interrupt_descriptor *interrupt_descriptor = &interrupt_descriptors[vector];
 
     // present bit must be set for descriptor to be valid
     interrupt_descriptor->type_attributes |= 1 << 15;
diff --git a/kernel/src/arch/x86_64/cpu/idt.h b/kernel/src/arch/x86_64/cpu/idt.h
index bed760e..c2f1d9c 100644
--- a/kernel/src/arch/x86_64/cpu/idt.h
+++ b/kernel/src/arch/x86_64/cpu/idt.h
@@ -24,6 +24,6 @@ enum gate_type {
     TRAP_64_GATE = 0xF
 };
 
-void setup_interrupt_gate(uint32_t irq, void *base, enum gate_type type, uint8_t privilege_level, uint8_t ist);
+void setup_interrupt_gate(uint32_t vector, void *base, enum gate_type type, uint8_t privilege_level, uint8_t ist);
 
 void load_idt(void);
diff --git a/kernel/src/arch/x86_64/drivers/keyboard/keyboard.c b/kernel/src/arch/x86_64/drivers/keyboard/keyboard.c
index e2d9fab..112c99e 100644
--- a/kernel/src/arch/x86_64/drivers/keyboard/keyboard.c
+++ b/kernel/src/arch/x86_64/drivers/keyboard/keyboard.c
@@ -64,7 +64,7 @@ enum scan_set_one {
 
 #define MAX_BUFFER_SIZE 512
 static char buffer[MAX_BUFFER_SIZE];
-static size_t buffer_pos = 0;
+static volatile size_t buffer_pos = 0;
 
 static __attribute__((interrupt)) void keyboard_handler(struct interrupt_frame *frame);
 
@@ -77,7 +77,6 @@ static bool shift_pressed = false;
 // TODO: use acpi to check if 8042 ps/2 controller is supported
 // todo: poll for keyboard status
 // todo: check keyboard type (1, 2, 3)
-// todo: detect if key is capital or nah (need to detect caps lock and shift)
 
 void keyboard_init(void) {
     // Disable any devices connected to ps/2 ports
@@ -138,7 +137,7 @@ static char keyboard_convert_code(char data) {
 
 // todo: WRITE A FRONTEND FUNCTION FOR KLIB
 char getc(void) {
-    while (buffer_pos == 0) {
+    while (!buffer_pos) {
         __builtin_ia32_pause();
     }
     char data = buffer[--buffer_pos];
@@ -198,10 +197,10 @@ static void keyboard_handler(struct interrupt_frame *frame) {
     uint8_t data = keyboard_code_set_1(inb(DATA_PORT));
     if (data >= 'A' && data <= 'Z' && !caps_lock) data += 32;
     data = keyboard_shift_conversion(data);
-    if ((data >= ' ' && data <= '~') || data == '\b' || data == '\t') buffer[buffer_pos++] = data;
+    if ((data >= ' ' && data <= '~') || data == '\b' || data == '\t' || data == '\n') buffer[buffer_pos++] = data;
     // ! minor bug: could loop over and getc wont be able to get the prev 512 chars
     buffer_pos %= MAX_BUFFER_SIZE;
     //if (data >= ' ' && data <= '~')
-    //    krintf("Keyboard pressed %c\n", data);
+    //    krintf("Keyboard pressed %c %d\n", data, buffer_pos);
     send_apic_eoi();
 }
diff --git a/kernel/src/arch/x86_64/drivers/mouse/mouse.c b/kernel/src/arch/x86_64/drivers/mouse/mouse.c
new file mode 100644
index 0000000..6e94ef2
--- /dev/null
+++ b/kernel/src/arch/x86_64/drivers/mouse/mouse.c
@@ -0,0 +1,122 @@
+#include "mouse.h"
+
+
+#include "../../../../io.h"
+#include "../../apic/ioapic.h"
+#include "../../apic/lapic.h"
+#include "../../cpu/idt.h"
+#include "../../klib/klib.h"
+#include "../../serial/serial.h"
+
+#define DATA_PORT        0x60
+#define STATUS_REGISTER  0x64
+#define COMMAND_REGISTER STATUS_REGISTER
+
+
+#define MOUSE_COMMAND          0xD4
+#define MOUSE_BIT              0x20
+#define GET_COMPAQ_STATUS_BYTE 0x20
+
+static bool right_button = false;
+static bool left_button = false;
+static bool middle_button = false;
+static bool x_sign = false;
+static bool y_sign = false;
+static uint8_t x_movement = 0;
+static uint8_t y_movement = 0;
+
+static __attribute__((interrupt)) void mouse_handler(struct interrupt_frame *frame);
+static void wait_mouse(bool is_output);
+
+void mouse_init(void) {
+    // enable mouse
+    wait_mouse(true);
+    outb(COMMAND_REGISTER, 0xA8);
+
+    // enable aux port to generate irq 12 (according to osdev)
+    wait_mouse(true);
+    outb(COMMAND_REGISTER, GET_COMPAQ_STATUS_BYTE);
+
+    wait_mouse(false);
+    uint8_t status = inb(STATUS_REGISTER);
+    status |= 0x10; // Enable IRQ12
+    status ^= ~0x20;// Disable mouse clock
+
+    // todo: bundle wait_mouse and outb/inb into one function
+
+    // update status with compaq byte
+    wait_mouse(true);
+    outb(COMMAND_REGISTER, 0x60);
+    wait_mouse(true);
+    outb(DATA_PORT, status);
+
+    // set defaults for mouse
+    wait_mouse(true);
+    outb(COMMAND_REGISTER, MOUSE_COMMAND);
+    wait_mouse(true);
+    outb(DATA_PORT, 0xF6);
+
+    // enable packet streaming
+    wait_mouse(true);
+    outb(COMMAND_REGISTER, MOUSE_COMMAND);
+    wait_mouse(true);
+    outb(DATA_PORT, 0xF4);
+
+    int apic_id = apic_get_id();
+    ioapic_set_redirect((uintptr_t *) IOAPIC_VIRTUAL_ADDRESS, 12, 0x22, apic_id);
+    setup_interrupt_gate(0x22, mouse_handler, INTERRUPT_64_GATE, 0, 0);
+}
+
+
+// See: https://wiki.osdev.org/Mouse_Input#Waiting_to_Send_Bytes_to_Port_0x60_and_0x64
+static void wait_mouse(bool is_output) {
+    if (is_output) {
+        while (inb(STATUS_REGISTER) & 0x2) {
+            __builtin_ia32_pause();
+        }
+    } else {
+        while (!(inb(DATA_PORT) & 0x1)) {
+            __builtin_ia32_pause();
+        }
+    }
+}
+
+static void mouse_handler(struct interrupt_frame *frame) {
+    uint8_t status = inb(STATUS_REGISTER);
+    puts("Mouse interrupt\n");
+    size_t nth_byte = 0;
+
+    while (status & MOUSE_BIT) {
+        uint8_t data = inb(DATA_PORT);
+        switch (nth_byte) {
+            case 0:
+                right_button = data & 0x1;
+                left_button = data & 0x2;
+                middle_button = data & 0x4;
+                x_sign = data & 0x10;
+                y_sign = data & 0x20;
+                break;
+            case 1:
+                x_movement = data;
+                break;
+            case 2:
+                y_movement = data;
+                break;
+        }
+        nth_byte++;
+        nth_byte %= 3;
+        krintf(
+                "Mouse info\n"
+                "right button: %d\n"
+                "left button: %d\n"
+                "middle button: %d\n"
+                "x sign: %d\n"
+                "y sign: %d\n"
+                "x movement: %d\n"
+                "y movement: %d\n",
+                right_button, left_button, middle_button, x_sign, y_sign, x_movement, y_movement);
+        status = inb(STATUS_REGISTER);
+    }
+    puts("Finished mouse interrupt\n");
+    send_apic_eoi();
+}
diff --git a/kernel/src/arch/x86_64/drivers/mouse/mouse.h b/kernel/src/arch/x86_64/drivers/mouse/mouse.h
new file mode 100644
index 0000000..7a24b3c
--- /dev/null
+++ b/kernel/src/arch/x86_64/drivers/mouse/mouse.h
@@ -0,0 +1,3 @@
+#pragma once
+
+void mouse_init(void);
diff --git a/kernel/src/kernel_main.c b/kernel/src/kernel_main.c
index d022440..cc84f0a 100644
--- a/kernel/src/kernel_main.c
+++ b/kernel/src/kernel_main.c
@@ -9,6 +9,7 @@
 #include "arch/x86_64/cpu/idt.h"
 #include "arch/x86_64/cpu/msr.h"
 #include "arch/x86_64/drivers/keyboard/keyboard.h"
+#include "arch/x86_64/drivers/mouse/mouse.h"
 #include "arch/x86_64/drivers/timer/timer.h"
 #include "arch/x86_64/klib/klib.h"
 #include "arch/x86_64/memory/paging.h"
@@ -200,6 +201,8 @@ static void setup_idt(void) {
     // we have interrupt after 31 since 0-31 are reserved for errors
     setup_interrupt_gate(0x20, timer_handler, INTERRUPT_64_GATE, 0, 0);
     keyboard_init();
+    // as of now mouse breaks keyboard and it doesnt work
+    mouse_init();
     setup_interrupt_gate(0x80, trap, TRAP_64_GATE, 3, 0);
 
     load_idt();

From 31a145f2634f8beb0f22620a678385d9e2358102 Mon Sep 17 00:00:00 2001
From: Oliver Po <oliver.po2882@gmail.com>
Date: Mon, 24 Feb 2025 15:23:15 +1100
Subject: [PATCH 22/22] (WIP) Refactor code for timer

---
 CMakeLists.txt                                |   2 +
 kernel/CMakeLists.txt                         |   3 +-
 kernel/src/arch/x86_64/acpi/acpi.c            |  95 +++++++++++----
 kernel/src/arch/x86_64/acpi/acpi.h            |  29 +++++
 kernel/src/arch/x86_64/apic/lapic.c           |  22 ----
 kernel/src/arch/x86_64/apic/lapic.h           |  10 +-
 kernel/src/arch/x86_64/drivers/pci/pci.c      |  76 ++++++++++++
 kernel/src/arch/x86_64/drivers/pci/pci.h      | 109 ++++++++++++++++++
 .../src/arch/x86_64/drivers/speaker/speaker.c |  14 +++
 .../src/arch/x86_64/drivers/speaker/speaker.h |   3 +
 kernel/src/arch/x86_64/drivers/timer/apic.c   |  33 ++++++
 kernel/src/arch/x86_64/drivers/timer/pit.c    |   8 ++
 kernel/src/arch/x86_64/drivers/timer/timer.c  |  13 ---
 kernel/src/arch/x86_64/drivers/timer/timer.h  |  10 +-
 kernel/src/arch/x86_64/klib/klib.c            |   6 +-
 kernel/src/arch/x86_64/serial/serial.c        |  10 ++
 kernel/src/arch/x86_64/serial/serial.h        |   6 +
 kernel/src/kernel_main.c                      |  16 ++-
 18 files changed, 395 insertions(+), 70 deletions(-)
 create mode 100644 kernel/src/arch/x86_64/drivers/pci/pci.c
 create mode 100644 kernel/src/arch/x86_64/drivers/pci/pci.h
 create mode 100644 kernel/src/arch/x86_64/drivers/speaker/speaker.c
 create mode 100644 kernel/src/arch/x86_64/drivers/speaker/speaker.h
 create mode 100644 kernel/src/arch/x86_64/drivers/timer/apic.c
 create mode 100644 kernel/src/arch/x86_64/drivers/timer/pit.c
 delete mode 100644 kernel/src/arch/x86_64/drivers/timer/timer.c

diff --git a/CMakeLists.txt b/CMakeLists.txt
index d448ce8..5ef2837 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -29,6 +29,8 @@ add_custom_target(run
                 -drive file=os.img,format=raw
                 -serial stdio
                 -device isa-debug-exit,iobase=0xf4,iosize=0x04
+                -netdev user,id=net0
+                -device virtio-net-pci,netdev=net0
                 -d int
                 -D qemu.log
         DEPENDS os)
diff --git a/kernel/CMakeLists.txt b/kernel/CMakeLists.txt
index c2e2cab..c45ed28 100644
--- a/kernel/CMakeLists.txt
+++ b/kernel/CMakeLists.txt
@@ -15,7 +15,8 @@ set(COMPILE_OPTIONS
 add_library(drivers OBJECT
         src/arch/x86_64/drivers/keyboard/keyboard.c
         src/arch/x86_64/drivers/mouse/mouse.c
-        src/arch/x86_64/drivers/timer/timer.c
+        src/arch/x86_64/drivers/pci/pci.c
+        src/arch/x86_64/drivers/timer/apic.c
         src/arch/x86_64/klib/trap.c
 )
 
diff --git a/kernel/src/arch/x86_64/acpi/acpi.c b/kernel/src/arch/x86_64/acpi/acpi.c
index e0127dd..38b59ca 100644
--- a/kernel/src/arch/x86_64/acpi/acpi.c
+++ b/kernel/src/arch/x86_64/acpi/acpi.c
@@ -67,44 +67,59 @@ bool rsdt_map(void) {
     return verify_mapping(KERNEL_MAPPING_ADDRESS | address);
 }
 
-bool rsdt_verify(void) {
-    struct rsdt *rsdt =
-            (struct rsdt *) (KERNEL_MAPPING_ADDRESS | rsdp->rsdt_address);
+static bool rsdt_entry_verify(void *entry) {
     uint8_t sum = 0;
-    for (size_t i = 0; i < rsdt->length; i++) {
-        sum += ((uint8_t *) rsdt)[i];
+    struct description_header *header = (struct description_header *) entry;
+    uint8_t *addr = (uint8_t *) entry;
+    for (size_t i = 0; i < header->length; i++) {
+        sum += addr[i];
     }
     return !sum;
 }
 
+bool rsdt_verify(void) {
+    struct rsdt *rsdt =
+            (struct rsdt *) (KERNEL_MAPPING_ADDRESS | rsdp->rsdt_address);
+    return rsdt_entry_verify(rsdt);
+}
+
 static size_t rsdt_get_entry_count(void) {
     struct rsdt *rsdt =
             (struct rsdt *) (KERNEL_MAPPING_ADDRESS | rsdp->rsdt_address);
     return (rsdt->length - sizeof(struct rsdt)) / sizeof(uint32_t);
 }
 
-#define MADT_SIGNATURE "APIC"
-
-static struct madt *madt = NULL;
-
-bool madt_find(void) {
+static void *rsdt_get_entry(char *signature) {
     size_t length = rsdt_get_entry_count();
     struct rsdt *rsdt =
             (struct rsdt *) (KERNEL_MAPPING_ADDRESS | rsdp->rsdt_address);
 
     for (size_t i = 0; i < length; i++) {
+        // todo: pre map
         map_page(KERNEL_MAPPING_ADDRESS | (uint64_t) rsdt->entry[i],
                  (uint64_t) rsdt->entry[i], PAGE_PRESENT);
 
         struct description_header *description_header =
                 (struct description_header *) (KERNEL_MAPPING_ADDRESS |
                                                (uint64_t) rsdt->entry[i]);
-        if (cmp_signature(description_header->signature, MADT_SIGNATURE)) {
-            madt = (struct madt *) (uint64_t) rsdt->entry[i];
-            return true;
+        if (cmp_signature(description_header->signature, signature)) {
+            return (void *) rsdt->entry[i];
         }
     }
-    return false;
+    return NULL;
+}
+
+#define MADT_SIGNATURE "APIC"
+
+static struct madt *madt = NULL;
+
+bool madt_find(void) {
+    madt = rsdt_get_entry(MADT_SIGNATURE);
+    return madt != NULL;
+}
+
+bool madt_verify(void) {
+    return rsdt_entry_verify(madt);
 }
 
 bool madt_map(void) {
@@ -114,15 +129,6 @@ bool madt_map(void) {
     return verify_mapping(KERNEL_MAPPING_ADDRESS | address);
 }
 
-bool madt_verify(void) {
-    uint8_t sum = 0;
-    uint8_t *addr = (uint8_t *) madt;
-    for (size_t i = 0; i < madt->length; i++) {
-        sum += addr[i];
-    }
-    return !sum;
-}
-
 uint32_t madt_get_lapic_address(void) {
     return madt->local_interrupt_controller_address;
 }
@@ -131,6 +137,8 @@ static struct madt_entry **madt_entries = NULL;
 static size_t max_madt_entries = 0;
 
 size_t ioapic_count_entries(void) {
+    if (madt_entries != NULL) return max_madt_entries;
+
     // all entries are after madt
     struct madt_entry *madt_entry =
             (struct madt_entry *) ((uint8_t *) madt + sizeof(struct madt));
@@ -156,3 +164,44 @@ size_t ioapic_count_entries(void) {
 struct madt_entry **get_madt_entries(void) {
     return madt_entries;
 }
+
+#define MCFG_SIGNATURE "MCFG"
+
+static struct mcfg *mcfg = NULL;
+
+bool mcfg_find(void) {
+    mcfg = rsdt_get_entry(MCFG_SIGNATURE);
+    return mcfg != NULL;
+}
+
+bool mcfg_verify(void) {
+    return rsdt_entry_verify(mcfg);
+}
+
+bool mcfg_map(void) {
+    uint64_t address = (uint64_t) mcfg;
+    map_page(KERNEL_MAPPING_ADDRESS | address, address, PAGE_PRESENT);
+    mcfg = (struct mcfg *) (KERNEL_MAPPING_ADDRESS | address);
+    return verify_mapping(KERNEL_MAPPING_ADDRESS | address);
+}
+
+static struct mcfg_entry **mcfg_entries = NULL;
+static size_t max_mcfg_entries = 0;
+
+size_t mcfg_count_entries(void) {
+    if (mcfg_entries != NULL) return max_madt_entries;
+
+    struct mcfg_entry *mcfg_entry =
+            (struct mcfg_entry *) ((uint8_t *) mcfg + sizeof(struct mcfg));
+
+    uint8_t *end = (uint8_t *) mcfg + mcfg->length;
+    max_mcfg_entries = (end - (uint8_t *) mcfg_entry) / sizeof(struct mcfg_entry);
+
+    mcfg_entries = kmalloc(sizeof(*mcfg_entries) * max_mcfg_entries);
+
+    for (size_t i = 0; (uint8_t *) mcfg_entry < end; i++) {
+        mcfg_entries[i] = mcfg_entry;
+        mcfg_entry = (struct mcfg_entry *) ((uint8_t *) mcfg_entry + sizeof(struct mcfg_entry));
+    }
+    return max_madt_entries;
+}
diff --git a/kernel/src/arch/x86_64/acpi/acpi.h b/kernel/src/arch/x86_64/acpi/acpi.h
index b88d6b8..5cde896 100644
--- a/kernel/src/arch/x86_64/acpi/acpi.h
+++ b/kernel/src/arch/x86_64/acpi/acpi.h
@@ -67,6 +67,23 @@ struct madt_entry_apicio {
     uint32_t global_system_interrupt_base;
 } __attribute__((packed));
 
+struct mcfg_entry {
+    uint64_t address;
+    // PCI segment group number
+    uint16_t pci_group;
+    uint8_t start_PCI_bus;
+    uint8_t end_PCI_bus;
+    uint32_t reserved;
+} __attribute__((packed));
+
+// from here: https://wiki.osdev.org/PCI_Express
+// not specified in ACPI spec (probs needs to find it in pcie spec)
+struct mcfg {
+    DESCRIPTION_HEADER
+    uint8_t reserved[8];
+    struct mcfg_entry data[];
+} __attribute__((packed));
+
 // Finds the rsdp and sets the address
 bool rsdp_find(void);
 
@@ -102,3 +119,15 @@ size_t ioapic_count_entries(void);
 
 // Returns a array of addresses to madts
 struct madt_entry **get_madt_entries(void);
+
+// Finds the mcfg 
+bool mcfg_find(void);
+
+// Verifies the mcfg
+bool mcfg_verify(void);
+
+// Maps the mcfg to a virtual memory address
+bool mcfg_map(void);
+
+// Counts the entries of the mcfg
+size_t mcfg_count_entries(void);
diff --git a/kernel/src/arch/x86_64/apic/lapic.c b/kernel/src/arch/x86_64/apic/lapic.c
index 0e0f780..fd1e835 100644
--- a/kernel/src/arch/x86_64/apic/lapic.c
+++ b/kernel/src/arch/x86_64/apic/lapic.c
@@ -2,7 +2,6 @@
 
 #include "../cpu/cpuid.h"
 #include "../cpu/msr.h"
-#include "../memory/paging.h"
 #include "../serial/serial.h"
 
 #define IA32_APIC_BASE_MSR        0x1B
@@ -39,8 +38,6 @@ static uintptr_t cpu_get_apic_base(void) {
 // todo: read from acpi to figure out ioapicbase
 // todo: since its not guaranteed to be same in all systems
 
-#define BASE_LAPIC 0xFEE00000
-
 void write_reg(void *lapicbase, uint32_t reg, uint32_t value) {
     uint32_t volatile *lapic = (uint32_t volatile *) lapicbase;
     lapic[reg] = value;
@@ -56,8 +53,6 @@ uint32_t read_reg(void *lapicbase, uint32_t reg) {
 #define PIC1_DATA (PIC1 + 1)
 #define PIC2_DATA (PIC2 + 1)
 
-#define LAPIC_VIRTUAL_ADDRESS (KERNEL_MAPPING_ADDRESS | BASE_LAPIC)
-
 bool map_apic(void) {
     map_page(LAPIC_VIRTUAL_ADDRESS, BASE_LAPIC,
              PAGE_PRESENT | PAGE_WRITE | PAGE_CACHE_DISABLE);
@@ -78,20 +73,3 @@ void enable_apic(void) {
 void send_apic_eoi(void) {
     *(uint32_t volatile *) (LAPIC_VIRTUAL_ADDRESS + 0xB0) = 0;
 }
-
-// Refer to Intel IA-32 Volume 3 12.5.4 APIC Timer
-void init_apic_timer(uint32_t initial_count, uint8_t vector) {
-    // be divisble by 1 (every 10ms) (Figure 12-10)
-    *(uint32_t volatile *) (LAPIC_VIRTUAL_ADDRESS + 0x3E0) = 1011;
-    // set initial count (Figure 12-11)
-    *(uint32_t volatile *) (LAPIC_VIRTUAL_ADDRESS + 0x380) = initial_count;
-// Refer to 12.5.1 (Timer mode and vector in Figure 12-8)
-// 0 = one shot, 1 = periodic, 2 = TSC-deadline
-#define APIC_TIMER_MODE 0
-    *(uint32_t volatile *) (LAPIC_VIRTUAL_ADDRESS + 0x320) =
-            vector | (APIC_TIMER_MODE << 17);
-}
-
-uint32_t get_apic_timer_current(void) {
-    return *(uint32_t volatile *) (LAPIC_VIRTUAL_ADDRESS + 0x390);
-}
diff --git a/kernel/src/arch/x86_64/apic/lapic.h b/kernel/src/arch/x86_64/apic/lapic.h
index 4b89871..51098aa 100644
--- a/kernel/src/arch/x86_64/apic/lapic.h
+++ b/kernel/src/arch/x86_64/apic/lapic.h
@@ -3,6 +3,11 @@
 #include <stdbool.h>
 #include <stdint.h>
 
+#include "../memory/paging.h"
+
+#define BASE_LAPIC            0xFEE00000
+#define LAPIC_VIRTUAL_ADDRESS (KERNEL_MAPPING_ADDRESS | BASE_LAPIC)
+
 // Checks whether apic is supported
 bool apic_is_supported(void);
 
@@ -24,8 +29,3 @@ void write_reg(void *ioapicaddr, uint32_t reg, uint32_t value);
 // Signal end of interrupt to apic
 void send_apic_eoi(void);
 
-// Initialises the apic timer
-void init_apic_timer(uint32_t initial_count, uint8_t vector);
-
-// Get the current count of apic timer
-uint32_t get_apic_timer_current(void);
diff --git a/kernel/src/arch/x86_64/drivers/pci/pci.c b/kernel/src/arch/x86_64/drivers/pci/pci.c
new file mode 100644
index 0000000..ce8f24a
--- /dev/null
+++ b/kernel/src/arch/x86_64/drivers/pci/pci.c
@@ -0,0 +1,76 @@
+#include "pci.h"
+
+#include <stddef.h>
+
+#include "../../klib/klib.h"
+#include "../../serial/serial.h"
+
+#include "../../../../io.h"
+
+#define CONFIG_ADDRESS 0xCF8
+#define CONFIG_DATA    0xCFC
+
+static struct common_header *devices = NULL;
+static size_t i = 0;
+
+// todo: support PCIE once I figure out a way
+// todo: to enable pcie in qemu
+
+// ! THIS ASSUMES WE ARE USING MECHANISM 1
+// ! MECHANISM 2 is deprecated
+
+// See: https://wiki.osdev.org/PCI
+uint32_t pci_config_readl(uint8_t bus, uint8_t slot, uint8_t func, uint8_t offset) {
+    uint32_t address = 0;
+    address |= bus << 16;
+    address |= slot << 11;
+    address |= func << 8;
+    address |= offset & 0xFC;
+    address |= 1 << 31;
+    outl(CONFIG_ADDRESS, address);
+    return inl(CONFIG_DATA);
+}
+
+struct common_header pci_get_config(uint8_t bus, uint8_t slot, uint8_t func) {
+    struct common_header header = {0};
+
+    // abuses little endian
+    ((uint32_t *) &header)[offsetof(struct common_header, vendor_ID) / sizeof(uint32_t)] =
+            pci_config_readl(bus, slot, func, 0x0);
+    ((uint32_t *) &header)[offsetof(struct common_header, command) / sizeof(uint32_t)] =
+            pci_config_readl(bus, slot, func, 0x4);
+    ((uint32_t *) &header)[offsetof(struct common_header, revision_ID) / sizeof(uint32_t)] =
+            pci_config_readl(bus, slot, func, 0x8);
+    ((uint32_t *) &header)[offsetof(struct common_header, cache_line_size) / sizeof(uint32_t)] =
+            pci_config_readl(bus, slot, func, 0xC);
+
+    return header;
+}
+
+void pci_check_slot(uint8_t bus, uint8_t slot) {
+    // todo: expand upon this
+    for (size_t func = 0; func < 8; func++) {
+        struct common_header header = pci_get_config(bus, slot, func);
+        if (header.vendor_ID == 0xFFFF) return;
+        if ((header.header_type & 0x80) == 0)
+            if (func != 0) continue;
+
+        krintf("Found device at bus %d slot %d function %d\n"
+               "Vendor ID: %d, Device ID: %d\n",
+               bus, slot, func,
+               header.vendor_ID, header.device_ID);
+        devices[i++] = header;
+    }
+}
+
+void pci_scan(void) {
+    // bruteforce method - hopefully we dont have more than 32 devices connected
+    // todo: have a method to figure out how many devices are connected
+    devices = kmalloc(32 * sizeof(struct common_header));
+    for (size_t bus = 0; bus < 256; bus++) {
+        for (size_t slot = 0; slot < 32; slot++) {
+            pci_check_slot(bus, slot);
+        }
+    }
+    i = 0;
+}
diff --git a/kernel/src/arch/x86_64/drivers/pci/pci.h b/kernel/src/arch/x86_64/drivers/pci/pci.h
new file mode 100644
index 0000000..9e14042
--- /dev/null
+++ b/kernel/src/arch/x86_64/drivers/pci/pci.h
@@ -0,0 +1,109 @@
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#define COMMON_HEADER        \
+    uint16_t vendor_ID;      \
+    uint16_t device_ID;      \
+    uint16_t command;        \
+    uint16_t status;         \
+    uint8_t revision_ID;     \
+    uint8_t prog_IF;         \
+    uint8_t subclass;        \
+    uint8_t class_code;      \
+    uint8_t cache_line_size; \
+    uint8_t latency_timer;   \
+    uint8_t header_type;     \
+    uint8_t BIST;
+
+
+struct common_header {
+    COMMON_HEADER
+    //    uint8_t data[];
+} __attribute__((packed));
+
+struct device_header {
+    COMMON_HEADER
+    uint32_t base_addresses[6];
+    uint32_t cardbus_cis_pointer;
+    uint16_t subsystem_vendor_ID;
+    uint16_t subsystem_device_ID;
+    uint32_t expansion_rom_address;
+    uint8_t capabilities_pointer;
+    uint8_t reserved0;
+    uint16_t reserved1;
+    uint32_t reserved2;
+    uint8_t interrupt_line;
+    uint8_t interrupt_pin;
+    uint8_t min_grant;
+    uint8_t max_latency;
+} __attribute__((packed));
+
+// pci to pci
+struct pci_bridge_header {
+    COMMON_HEADER
+    uint32_t base_addresses[2];
+    uint8_t primary_bus_number;
+    uint8_t secondary_bus_number;
+    uint8_t subordinate_bus_number;
+    uint8_t secondary_latency_timer;
+    uint8_t io_base;
+    uint8_t io_limit;
+    uint8_t secondary_status;
+    uint16_t memory_base;
+    uint16_t memory_limit;
+    uint16_t prefetchable_memory_base;
+    uint16_t prefetchable_memory_limit;
+    uint32_t prefetchable_memory_base_upper;
+    uint32_t prefetchable_memory_limit_upper;
+    uint16_t io_base_upper;
+    uint16_t io_limit_upper;
+    uint8_t capabilities_pointer;
+    uint8_t reserved0;
+    uint16_t reserved1;
+    uint32_t expansion_ROM_base_address;
+    uint8_t interrupt_line;
+    uint8_t interrupt_pin;
+    uint16_t bridge_control;
+} __attribute__((packed));
+
+// pci to cardbus
+struct cardbus_bridge_header {
+    COMMON_HEADER
+    uint32_t base_address;
+    uint8_t offset_capabilities_list;
+    uint8_t reserved0;
+    uint16_t secondary_status;
+    uint8_t pci_bus_number;
+    uint8_t cardbus_bus_number;
+    uint8_t subordinate_bus_number;
+    uint8_t cardbus_latency_timer;
+    uint32_t memory_base_address0;
+    uint32_t memory_limit0;
+    uint32_t memory_base_address1;
+    uint32_t memory_limit1;
+    uint32_t io_base_address0;
+    uint32_t io_limit0;
+    uint32_t io_base_address1;
+    uint32_t io_limit1;
+    uint8_t interrupt_line;
+    uint8_t interrupt_pin;
+    uint16_t bridge_control;
+    uint16_t subsystem_device_ID;
+    uint16_t subsystem_vendor_ID;
+    // 16 bit pc card
+    uint32_t legacy_mode_base_address;
+} __attribute__((packed));
+
+uint32_t pci_config_readl(uint8_t bus, uint8_t slot, uint8_t func, uint8_t offset);
+
+void pci_scan(void);
+
+struct common_header pci_get_config(uint8_t bus, uint8_t slot, uint8_t func);
+
+void pci_check_slot(uint8_t bus, uint8_t slot);
+
+void pci_init(void);
+
+bool pci_msi_supported(void);
diff --git a/kernel/src/arch/x86_64/drivers/speaker/speaker.c b/kernel/src/arch/x86_64/drivers/speaker/speaker.c
new file mode 100644
index 0000000..30b994f
--- /dev/null
+++ b/kernel/src/arch/x86_64/drivers/speaker/speaker.c
@@ -0,0 +1,14 @@
+#include <stdint.h>
+
+#include "../../serial/serial.h"
+
+// frequency of PIT oscillator
+#define FREQUENCY_BASE 1193180
+
+#define SPEAKER_PORT 0x61
+
+
+static void speaker_play_sound(uint32_t frequency) {
+    uint32_t div = FREQUENCY_BASE / frequency;
+
+}
diff --git a/kernel/src/arch/x86_64/drivers/speaker/speaker.h b/kernel/src/arch/x86_64/drivers/speaker/speaker.h
new file mode 100644
index 0000000..20bf192
--- /dev/null
+++ b/kernel/src/arch/x86_64/drivers/speaker/speaker.h
@@ -0,0 +1,3 @@
+#pragma once
+
+#include <stdint.h>
diff --git a/kernel/src/arch/x86_64/drivers/timer/apic.c b/kernel/src/arch/x86_64/drivers/timer/apic.c
new file mode 100644
index 0000000..4359c7c
--- /dev/null
+++ b/kernel/src/arch/x86_64/drivers/timer/apic.c
@@ -0,0 +1,33 @@
+#include "timer.h"
+
+#include "../../apic/lapic.h"
+
+static uint32_t timer_ticks = 0;
+
+// Refer to Intel IA-32 Volume 3 12.5.4 APIC Timer
+void apic_timer_init(uint32_t initial_count, uint8_t vector) {
+    // be divisble by 1 (every 10ms) (Figure 12-10)
+    *(uint32_t volatile *) (LAPIC_VIRTUAL_ADDRESS + 0x3E0) = 1011;
+    // set initial count (Figure 12-11)
+    *(uint32_t volatile *) (LAPIC_VIRTUAL_ADDRESS + 0x380) = initial_count;
+// Refer to 12.5.1 (Timer mode and vector in Figure 12-8)
+// 0 = one shot, 1 = periodic, 2 = TSC-deadline
+#define APIC_TIMER_MODE 0
+    *(uint32_t volatile *) (LAPIC_VIRTUAL_ADDRESS + 0x320) =
+            vector | (APIC_TIMER_MODE << 17);
+}
+
+// returns time left from countdown iirc
+uint32_t apic_timer_get_current(void) {
+    return *(uint32_t volatile *) (LAPIC_VIRTUAL_ADDRESS + 0x390);
+}
+
+
+uint32_t apic_timer_get_ticks(void) {
+    return timer_ticks;
+}
+
+__attribute__((interrupt)) void apic_timer_handler(struct interrupt_frame *frame) {
+    timer_ticks++;
+    send_apic_eoi();
+}
diff --git a/kernel/src/arch/x86_64/drivers/timer/pit.c b/kernel/src/arch/x86_64/drivers/timer/pit.c
new file mode 100644
index 0000000..1f0680d
--- /dev/null
+++ b/kernel/src/arch/x86_64/drivers/timer/pit.c
@@ -0,0 +1,8 @@
+#include "timer.h"
+
+#include "../../apic/ioapic.h"
+
+__attribute__((interrupt)) void pit_handler(struct interrupt_frame *frame) {
+    
+    send_apic_eoi();
+}
diff --git a/kernel/src/arch/x86_64/drivers/timer/timer.c b/kernel/src/arch/x86_64/drivers/timer/timer.c
deleted file mode 100644
index 1b4bc31..0000000
--- a/kernel/src/arch/x86_64/drivers/timer/timer.c
+++ /dev/null
@@ -1,13 +0,0 @@
-#include "timer.h"
-
-#include "../../apic/lapic.h"
-
-static int timer_ticks = 0;
-
-uint32_t get_timer_ticks(void) {
-    return timer_ticks;
-}
-
-__attribute__((interrupt)) void timer_handler(struct interrupt_frame *frame) {
-    send_apic_eoi();
-}
diff --git a/kernel/src/arch/x86_64/drivers/timer/timer.h b/kernel/src/arch/x86_64/drivers/timer/timer.h
index ece4711..c22a780 100644
--- a/kernel/src/arch/x86_64/drivers/timer/timer.h
+++ b/kernel/src/arch/x86_64/drivers/timer/timer.h
@@ -3,9 +3,15 @@
 #include <stdint.h>
 
 // Returns the timer
-uint32_t get_timer_ticks(void);
+uint32_t apic_timer_get_ticks(void);
 
 struct interrupt_frame;
 
 // Timer handler
-void timer_handler(struct interrupt_frame *frame);
+void apic_timer_handler(struct interrupt_frame *frame);
+
+// Initialises the apic timer
+void apic_timer_init(uint32_t initial_count, uint8_t vector);
+
+// Get the current count of apic timer
+uint32_t apic_timer_get_current(void);
diff --git a/kernel/src/arch/x86_64/klib/klib.c b/kernel/src/arch/x86_64/klib/klib.c
index d144e9a..97c4342 100644
--- a/kernel/src/arch/x86_64/klib/klib.c
+++ b/kernel/src/arch/x86_64/klib/klib.c
@@ -1,10 +1,10 @@
 #include "klib.h"
 
-#include "../apic/lapic.h"
+#include "../drivers/timer/timer.h"
 
 void ksleep(int ticks) {
-    init_apic_timer(ticks, 0x20);
-    while (get_apic_timer_current());
+    apic_timer_init(ticks, 0x20);
+    while (apic_timer_get_current());
 }
 
 _Noreturn void _die(void) {
diff --git a/kernel/src/arch/x86_64/serial/serial.c b/kernel/src/arch/x86_64/serial/serial.c
index d06ca72..083518a 100644
--- a/kernel/src/arch/x86_64/serial/serial.c
+++ b/kernel/src/arch/x86_64/serial/serial.c
@@ -8,8 +8,18 @@ void outw(uint16_t port, uint16_t value) {
     asm volatile("outw %w0, %w1" : : "a"(value), "Nd"(port) : "memory");
 }
 
+void outl(uint16_t port, uint32_t value) {
+    asm volatile("outl %d0, %d1" : : "a"(value), "Nd"(port) : "memory");
+}
+
 uint8_t inb(uint16_t port) {
     uint8_t value;
     asm volatile("inb %w1, %b0" : "=a"(value) : "Nd"(port) : "memory");
     return value;
 }
+
+uint32_t inl(uint16_t port) {
+    uint32_t value;
+    asm volatile("inl %d1, %d0" : "=a"(value) : "Nd"(port) : "memory");
+    return value;
+}
diff --git a/kernel/src/arch/x86_64/serial/serial.h b/kernel/src/arch/x86_64/serial/serial.h
index 1b612a4..65209d5 100644
--- a/kernel/src/arch/x86_64/serial/serial.h
+++ b/kernel/src/arch/x86_64/serial/serial.h
@@ -8,5 +8,11 @@ void outb(uint16_t port, uint8_t value);
 // Writes a word to the serial port
 void outw(uint16_t port, uint16_t value);
 
+// Writes a long to the serial port
+void outl(uint16_t port, uint32_t value);
+
 // Reads a byte from the serial port
 uint8_t inb(uint16_t port);
+
+// Reads a long from the serial port
+uint32_t inl(uint16_t port);
diff --git a/kernel/src/kernel_main.c b/kernel/src/kernel_main.c
index cc84f0a..cc90fd0 100644
--- a/kernel/src/kernel_main.c
+++ b/kernel/src/kernel_main.c
@@ -10,6 +10,7 @@
 #include "arch/x86_64/cpu/msr.h"
 #include "arch/x86_64/drivers/keyboard/keyboard.h"
 #include "arch/x86_64/drivers/mouse/mouse.h"
+#include "arch/x86_64/drivers/pci/pci.h"
 #include "arch/x86_64/drivers/timer/timer.h"
 #include "arch/x86_64/klib/klib.h"
 #include "arch/x86_64/memory/paging.h"
@@ -107,6 +108,9 @@ void _Noreturn kernel_main(struct boot_parameters parameters) {
     krintf("String: %s\n", str);
     free(str);
 
+    pci_scan();
+    puts("Finished scanning for PCI devices\n");
+    getc();
 
     char message[] = "X Hello world!\n";
 
@@ -117,7 +121,7 @@ void _Noreturn kernel_main(struct boot_parameters parameters) {
         // ! DONT USE FLOATS - THEY DONT WORK FOR SOME REASON
 
         krintf("%sThe number is: %d, ticks: %d, entry count: %d\n", message, 5,
-               get_timer_ticks(), parameters.address_range_count);
+               apic_timer_get_ticks(), parameters.address_range_count);
 
         vga_set_color(1 + (i % 6), VGA_COLOR_BLACK);
         //memmap_print_entries(parameters.address_range_count,
@@ -184,6 +188,16 @@ static void read_acpi(void) {
             krintf("APICIO address: %x\n", apicio_entry->ioapic_address);
         }
     }
+
+    // Currently I don't know how to get pcie
+    // working with the qemu so we are falling back to pci
+    /*
+    if (!mcfg_find()) {
+        puts("Could not find mcfg\n");
+        _die();
+    }
+    puts("Found mcfg\n");
+    */
 }
 
 static void setup_idt(void) {