implement getpgid (#1090)

* implement getpgid syscall

Lind does not implement process groups. getpgid always returns the
cage's own cageid (matching getpid behavior). This is platform-specific
behavior that cannot be changed with a grate since getpgid is handled
directly by RawPOSIX.

Fixes #775

* fix getpgid test to pass on native linux

* address review: remove unused includes, fix misleading comment

Author: rennergade

src/glibc/lind_syscall/lind_syscall_num.h

@@ -104,6 +104,7 @@
 #define GETEUID_SYSCALL 107
 #define GETEGID_SYSCALL 108
 #define GETPPID_SYSCALL 110
+#define GETPGID_SYSCALL 121
 #define MKNOD_SYSCALL 133
 #define STATFS_SYSCALL 137
 #define FSTATFS_SYSCALL 138

src/glibc/sysdeps/unix/sysv/linux/i386/i686/getpgid.c

@@ -1,9 +1,12 @@
 #include <unistd.h>
+#include <syscall-template.h>
+#include <lind_syscall_num.h>
 
 pid_t
 __getpgid (pid_t pid)
 {
-  return pid;
+  return MAKE_LEGACY_SYSCALL (GETPGID_SYSCALL, "syscall|getpgid",
+               (uint64_t) pid, NOTUSED, NOTUSED,
+               NOTUSED, NOTUSED, NOTUSED, TRANSLATE_ERRNO_ON);
 }
-
-
+weak_alias (__getpgid, getpgid)

src/rawposix/src/sys_calls.rs

@@ -676,6 +676,50 @@ pub extern "C" fn getpid_syscall(
     return cage.cageid as i32;
 }
 
+/// Reference to Linux: https://man7.org/linux/man-pages/man2/getpgid.2.html
+///
+/// Returns the process group ID of the process specified by pid.
+/// If pid is 0, returns the process group ID of the calling process.
+///
+/// Lind does not implement process groups. The default RawPOSIX behavior
+/// always returns the cage's own cageid. A grate can interpose on this
+/// syscall to provide different process group semantics.
+///
+/// ## Returns
+///     - The cageid (as process group ID) on success.
+pub extern "C" fn getpgid_syscall(
+    cageid: u64,
+    pid_arg: u64,
+    pid_cageid: u64,
+    arg2: u64,
+    arg2_cageid: u64,
+    arg3: u64,
+    arg3_cageid: u64,
+    arg4: u64,
+    arg4_cageid: u64,
+    arg5: u64,
+    arg5_cageid: u64,
+    arg6: u64,
+    arg6_cageid: u64,
+) -> i32 {
+    if !(sc_unusedarg(arg2, arg2_cageid)
+        && sc_unusedarg(arg3, arg3_cageid)
+        && sc_unusedarg(arg4, arg4_cageid)
+        && sc_unusedarg(arg5, arg5_cageid)
+        && sc_unusedarg(arg6, arg6_cageid))
+    {
+        panic!(
+            "{}: unused arguments contain unexpected values -- security violation",
+            "getpgid_syscall"
+        );
+    }
+
+    // Lind doesn't implement process groups. Return own cageid regardless
+    // of the pid argument (matching the behavior of getpid).
+    let cage = get_cage(cageid).unwrap();
+    cage.cageid as i32
+}
+
 /// Reference to Linux: https://man7.org/linux/man-pages/man3/getppid.3p.html
 ///
 /// See comments of `getpid_syscall` for more details

src/rawposix/src/syscall_table.rs

@@ -26,7 +26,7 @@ use super::net_calls::{
 };
 use super::sys_calls::{
     exec_syscall, exit_group_syscall, exit_syscall, fork_syscall, getegid_syscall, geteuid_syscall,
-    getgid_syscall, getpid_syscall, getppid_syscall, getuid_syscall, kill_syscall,
+    getgid_syscall, getpgid_syscall, getpid_syscall, getppid_syscall, getuid_syscall, kill_syscall,
     prlimit64_syscall, sched_yield_syscall, setitimer_syscall, sigaction_syscall,
     sigprocmask_syscall, waitpid_syscall,
 };
@@ -125,6 +125,7 @@ pub const SYSCALL_TABLE: &[(u64, RawCallFunc)] = &[
     (syscall_const::GETEUID_SYSCALL as u64, geteuid_syscall),
     (syscall_const::GETEGID_SYSCALL as u64, getegid_syscall),
     (syscall_const::GETPPID_SYSCALL as u64, getppid_syscall),
+    (syscall_const::GETPGID_SYSCALL as u64, getpgid_syscall),
     (syscall_const::MKNOD_SYSCALL as u64, mknod_syscall),
     (syscall_const::STATFS_SYSCALL as u64, statfs_syscall),
     (syscall_const::FSTATFS_SYSCALL as u64, fstatfs_syscall),

src/sysdefs/src/constants/syscall_const.rs

@@ -84,6 +84,7 @@ pub const GETGID_SYSCALL: i32 = 104;
 pub const GETEUID_SYSCALL: i32 = 107;
 pub const GETEGID_SYSCALL: i32 = 108;
 pub const GETPPID_SYSCALL: i32 = 110;
+pub const GETPGID_SYSCALL: i32 = 121;
 pub const MKNOD_SYSCALL: i32 = 133;
 pub const STATFS_SYSCALL: i32 = 137;
 pub const FSTATFS_SYSCALL: i32 = 138;

tests/unit-tests/file_tests/deterministic/getpgid.c

@@ -0,0 +1,11 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <assert.h>
+
+int main(void) {
+    pid_t pgid = getpgid(0);
+    assert(pgid > 0);
+
+    printf("getpgid: all tests passed\n");
+    return 0;
+}