Use naked_asm!, delete asm_func!

Cargo.toml

@@ -259,7 +259,6 @@ wasmtime-fiber = { path = "crates/fiber", version = "=38.0.0", package = 'wasmti
 wasmtime-jit-debug = { path = "crates/jit-debug", version = "=38.0.0", package = 'wasmtime-internal-jit-debug' }
 wasmtime-component-util = { path = "crates/component-util", version = "=38.0.0", package = 'wasmtime-internal-component-util' }
 wasmtime-component-macro = { path = "crates/component-macro", version = "=38.0.0", package = 'wasmtime-internal-component-macro' }
-wasmtime-asm-macros = { path = "crates/asm-macros", version = "=38.0.0", package = 'wasmtime-internal-asm-macros' }
 wasmtime-versioned-export-macros = { path = "crates/versioned-export-macros", version = "=38.0.0", package = 'wasmtime-internal-versioned-export-macros' }
 wasmtime-slab = { path = "crates/slab", version = "=38.0.0", package = 'wasmtime-internal-slab' }
 wasmtime-jit-icache-coherence = { path = "crates/jit-icache-coherence", version = "=38.0.0", package = 'wasmtime-internal-jit-icache-coherence' }

crates/fiber/Cargo.toml

@@ -15,7 +15,6 @@ workspace = true
 anyhow = { workspace = true }
 cfg-if = { workspace = true }
 wasmtime-versioned-export-macros = { workspace = true }
-wasmtime-asm-macros = { workspace = true }
 
 [target.'cfg(unix)'.dependencies]
 rustix = { workspace = true, features = ["mm"] }

crates/fiber/build.rs

@@ -22,10 +22,6 @@ fn main() {
         println!("cargo:rerun-if-changed=src/windows.c");
         build.file("src/windows.c");
         build.define("VERSIONED_SUFFIX", Some(versioned_suffix!()));
-    } else if arch == "s390x" {
-        println!("cargo:rerun-if-changed=src/stackswitch/s390x.S");
-        build.file("src/stackswitch/s390x.S");
-        build.define("VERSIONED_SUFFIX", Some(versioned_suffix!()));
     } else {
         // assume that this is included via inline assembly in the crate itself,
         // and the crate will otherwise have a `compile_error!` for unsupported

crates/fiber/src/lib.rs

@@ -22,6 +22,7 @@ cfg_if::cfg_if! {
     if #[cfg(not(feature = "std"))] {
         mod nostd;
         use nostd as imp;
+        mod stackswitch;
     } else if #[cfg(miri)] {
         mod miri;
         use miri as imp;
@@ -31,16 +32,12 @@ cfg_if::cfg_if! {
     } else if #[cfg(unix)] {
         mod unix;
         use unix as imp;
+        mod stackswitch;
     } else {
         compile_error!("fibers are not supported on this platform");
     }
 }
 
-// Our own stack switcher routines are used on Unix and no_std
-// platforms, but not on Windows (it has its own fiber API).
-#[cfg(any(unix, not(feature = "std")))]
-pub(crate) mod stackswitch;
-
 /// Represents an execution stack to use for a fiber.
 pub struct FiberStack(imp::FiberStack);
 

crates/fiber/src/stackswitch.rs

@@ -8,22 +8,27 @@ cfg_if::cfg_if! {
     if #[cfg(target_arch = "aarch64")] {
         mod aarch64;
         pub(crate) use supported::*;
+        pub(crate) use aarch64::*;
     } else if #[cfg(target_arch = "x86_64")] {
         mod x86_64;
         pub(crate) use supported::*;
+        pub(crate) use x86_64::*;
     } else if #[cfg(target_arch = "x86")] {
         mod x86;
         pub(crate) use supported::*;
+        pub(crate) use x86::*;
     } else if #[cfg(target_arch = "arm")] {
         mod arm;
         pub(crate) use supported::*;
+        pub(crate) use arm::*;
     } else if #[cfg(target_arch = "s390x")] {
-        // currently `global_asm!` isn't stable on s390x so this is an external
-        // assembler file built with the `build.rs`.
+        mod s390x;
         pub(crate) use supported::*;
+        pub(crate) use s390x::*;
     } else if #[cfg(target_arch = "riscv64")]  {
         mod riscv64;
         pub(crate) use supported::*;
+        pub(crate) use riscv64::*;
     } else {
         // No support for this platform. Don't fail compilation though and
         // instead defer the error to happen at runtime when a fiber is created.
@@ -42,18 +47,6 @@ cfg_if::cfg_if! {
 )]
 mod supported {
     pub const SUPPORTED_ARCH: bool = true;
-    unsafe extern "C" {
-        #[wasmtime_versioned_export_macros::versioned_link]
-        pub(crate) fn wasmtime_fiber_init(
-            top_of_stack: *mut u8,
-            entry: extern "C" fn(*mut u8, *mut u8),
-            entry_arg0: *mut u8,
-        );
-        #[wasmtime_versioned_export_macros::versioned_link]
-        pub(crate) fn wasmtime_fiber_switch(top_of_stack: *mut u8);
-        #[wasmtime_versioned_export_macros::versioned_link]
-        pub(crate) fn wasmtime_fiber_start();
-    }
 }
 
 /// Helper module reexported in the fallback case above when the current host

crates/fiber/src/stackswitch/aarch64.rs

@@ -18,8 +18,7 @@
 //   `DW_CFA_AARCH64_negate_ra_state` DWARF operation (aliased with the
 //   `.cfi_window_save` assembler directive) informs an unwinder about this
 
-use super::wasmtime_fiber_start;
-use wasmtime_asm_macros::asm_func;
+use core::arch::naked_asm;
 
 cfg_if::cfg_if! {
     if #[cfg(target_vendor = "apple")] {
@@ -37,10 +36,9 @@ cfg_if::cfg_if! {
     }
 }
 
-// fn(top_of_stack(%x0): *mut u8)
-asm_func!(
-    wasmtime_versioned_export_macros::versioned_stringify_ident!(wasmtime_fiber_switch),
-    concat!(
+#[unsafe(naked)]
+pub(crate) unsafe extern "C" fn wasmtime_fiber_switch(top_of_stack: *mut u8 /* x0 */) {
+    naked_asm!(concat!(
         "
             .cfi_startproc
         ",
@@ -87,14 +85,9 @@ asm_func!(
             ret
             .cfi_endproc
         ",
-    ),
-);
+    ));
+}
 
-// fn(
-//    top_of_stack(%x0): *mut u8,
-//    entry_point(%x1): extern fn(*mut u8, *mut u8),
-//    entry_arg0(%x2): *mut u8,
-// )
 // We set up the newly initialized fiber, so that it resumes execution
 // from wasmtime_fiber_start(). As a result, we need a signed address
 // of this function, so there are 2 requirements:
@@ -112,10 +105,14 @@ asm_func!(
 // TODO: Use the PACGA instruction to authenticate the saved register
 // state, which avoids creating signed pointers to
 // wasmtime_fiber_start(), and provides wider coverage.
-#[rustfmt::skip]
-asm_func!(
-    wasmtime_versioned_export_macros::versioned_stringify_ident!(wasmtime_fiber_init),
-    concat!(
+#[unsafe(naked)]
+pub(crate) unsafe extern "C" fn wasmtime_fiber_init(
+    top_of_stack: *mut u8,                        // x0
+    entry_point: extern "C" fn(*mut u8, *mut u8), // x1
+    entry_arg0: *mut u8,                          // x2
+) {
+    naked_asm!(
+        concat!(
         "
             .cfi_startproc
             hint #34 // bti c
@@ -136,16 +133,18 @@ asm_func!(
             ret
             .cfi_endproc
         ",
-    ),
-    fiber = sym wasmtime_fiber_start,
-);
+        ),
+        fiber = sym wasmtime_fiber_start,
+    );
+}
 
 // See the x86_64 file for more commentary on what these CFI directives are
 // doing. Like over there note that the relative offsets to registers here
 // match the frame layout in `wasmtime_fiber_switch`.
-asm_func!(
-    wasmtime_versioned_export_macros::versioned_stringify_ident!(wasmtime_fiber_start),
-    "
+#[unsafe(naked)]
+unsafe extern "C" fn wasmtime_fiber_start() -> ! {
+    naked_asm!(
+        "
         .cfi_startproc simple
         .cfi_def_cfa_offset 0
         .cfi_escape 0x0f,    /* DW_CFA_def_cfa_expression */ \
@@ -180,5 +179,6 @@ asm_func!(
         // codebase.
         brk 0xf1b3
         .cfi_endproc
-    ",
-);
+        ",
+    );
+}