arch: add i686 support

.github/workflows/rust.yml

@@ -47,6 +47,8 @@ jobs:
             toolchain: nightly
             components: rust-src
             build_std: true
+          - target: i686-unknown-linux-gnu
+            toolchain: stable
 
     steps:
     - name: "Checkout"

crates/asm/src/lib.rs

@@ -6,8 +6,8 @@
 //! faster?
 //!
 //! Supports `x86_64`, `aarch64`, `riscv64`, `loongarch64`, `s390x`,
-//! `powerpc64`, `arm` (armv7), `riscv32`, `sparc64`, and `mips64`
-//! architectures.
+//! `powerpc64`, `arm` (armv7), `riscv32`, `sparc64`, `mips64`, and `x86`
+//! (i686) architectures.
 
 #![no_std]
 #![cfg_attr(
@@ -30,11 +30,12 @@
   target_arch = "arm",
   target_arch = "riscv32",
   target_arch = "sparc64",
-  target_arch = "mips64"
+  target_arch = "mips64",
+  target_arch = "x86"
 )))]
 compile_error!(
   "Unsupported architecture: only x86_64, aarch64, riscv64, loongarch64, \
-   s390x, powerpc64, arm, riscv32, sparc64, and mips64 are supported"
+   s390x, powerpc64, arm, riscv32, sparc64, mips64, and x86 are supported"
 );
 
 // Per-arch syscall implementations live in their own module files.
@@ -68,6 +69,9 @@ mod arch;
 #[cfg(target_arch = "mips64")]
 #[path = "mips64.rs"]
 mod arch;
+#[cfg(target_arch = "x86")]
+#[path = "x86.rs"]
+mod arch;
 
 /// Copies `n` bytes from `src` to `dest`.
 ///
@@ -305,6 +309,7 @@ pub unsafe fn sys_uname(buf: *mut UtsNameBuf) -> i32 {
   target_arch = "s390x",
   target_arch = "arm",
   target_arch = "riscv32",
+  target_arch = "x86",
   target_arch = "mips64"
 )))]
 pub struct StatfsBuf {
@@ -347,7 +352,7 @@ pub struct StatfsBuf {
 /// on armv7 `statfs64(2)` has 32-bit word fields; see
 /// https://github.com/torvalds/linux/blob/v6.19/include/uapi/asm-generic/statfs.h
 #[repr(C)]
-#[cfg(any(target_arch = "arm", target_arch = "riscv32"))]
+#[cfg(any(target_arch = "arm", target_arch = "riscv32", target_arch = "x86"))]
 pub struct StatfsBuf {
   pub f_type:    u32,
   pub f_bsize:   u32,
@@ -455,7 +460,11 @@ pub fn read_file_fast(path: &str, buffer: &mut [u8]) -> Result<usize, i32> {
 /// The layout matches the kernel's `struct sysinfo` *exactly*:
 /// `mem_unit` ends at offset 108, then 4 bytes of implicit padding to 112.
 #[repr(C)]
-#[cfg(not(any(target_arch = "arm", target_arch = "riscv32")))]
+#[cfg(not(any(
+  target_arch = "arm",
+  target_arch = "riscv32",
+  target_arch = "x86"
+)))]
 pub struct SysInfo {
   pub uptime:    i64,
   pub loads:     [u64; 3],
@@ -479,7 +488,7 @@ pub struct SysInfo {
 /// on armv7 `__kernel_long_t` is 4 bytes; see
 /// https://github.com/torvalds/linux/blob/v6.19/include/uapi/linux/sysinfo.h
 #[repr(C)]
-#[cfg(any(target_arch = "arm", target_arch = "riscv32"))]
+#[cfg(any(target_arch = "arm", target_arch = "riscv32", target_arch = "x86"))]
 pub struct SysInfo {
   pub uptime:    i32,
   pub loads:     [u32; 3],

crates/asm/src/x86.rs

@@ -0,0 +1,149 @@
+//! Syscall implementations for `x86`.
+
+use super::{StatfsBuf, SysInfo, UtsNameBuf};
+
+pub(super) unsafe fn sys_open(path: *const u8, flags: i32) -> i32 {
+  unsafe {
+    let ret: i32;
+    core::arch::asm!(
+      "push ebx",
+      "mov ebx, {arg1:e}",
+      "int 0x80",
+      "pop ebx",
+      arg1 = in(reg) path,
+      inlateout("eax") 5i32 => ret,  // SYS_open
+      in("ecx") flags,
+      in("edx") 0i32,  // mode
+    );
+    ret
+  }
+}
+
+pub(super) unsafe fn sys_read(fd: i32, buf: *mut u8, count: usize) -> isize {
+  unsafe {
+    let ret: i32;
+    core::arch::asm!(
+      "push ebx",
+      "mov ebx, {arg1:e}",
+      "int 0x80",
+      "pop ebx",
+      arg1 = in(reg) fd,
+      inlateout("eax") 3i32 => ret,  // SYS_read
+      in("ecx") buf,
+      in("edx") count,
+    );
+    ret as isize
+  }
+}
+
+pub(super) unsafe fn sys_write(fd: i32, buf: *const u8, count: usize) -> isize {
+  unsafe {
+    let ret: i32;
+    core::arch::asm!(
+      "push ebx",
+      "mov ebx, {arg1:e}",
+      "int 0x80",
+      "pop ebx",
+      arg1 = in(reg) fd,
+      inlateout("eax") 4i32 => ret,  // SYS_write
+      in("ecx") buf,
+      in("edx") count,
+    );
+    ret as isize
+  }
+}
+
+pub(super) unsafe fn sys_close(fd: i32) -> i32 {
+  unsafe {
+    let ret: i32;
+    core::arch::asm!(
+      "push ebx",
+      "mov ebx, {arg1:e}",
+      "int 0x80",
+      "pop ebx",
+      arg1 = in(reg) fd,
+      inlateout("eax") 6i32 => ret,  // SYS_close
+    );
+    ret
+  }
+}
+
+pub(super) unsafe fn sys_uname(buf: *mut UtsNameBuf) -> i32 {
+  unsafe {
+    let ret: i32;
+    core::arch::asm!(
+      "push ebx",
+      "mov ebx, {arg1:e}",
+      "int 0x80",
+      "pop ebx",
+      arg1 = in(reg) buf,
+      inlateout("eax") 122i32 => ret,  // SYS_newuname
+    );
+    ret
+  }
+}
+
+pub(super) unsafe fn sys_statfs(path: *const u8, buf: *mut StatfsBuf) -> i32 {
+  unsafe {
+    let ret: i32;
+    core::arch::asm!(
+      "push ebx",
+      "mov ebx, {arg1:e}",
+      "int 0x80",
+      "pop ebx",
+      arg1 = in(reg) path,
+      inlateout("eax") 268i32 => ret,  // SYS_statfs64
+      in("ecx") core::mem::size_of::<StatfsBuf>(),
+      in("edx") buf,
+    );
+    ret
+  }
+}
+
+pub(super) unsafe fn sys_sysinfo(info: *mut SysInfo) -> i64 {
+  unsafe {
+    let ret: i32;
+    core::arch::asm!(
+      "push ebx",
+      "mov ebx, {arg1:e}",
+      "int 0x80",
+      "pop ebx",
+      arg1 = in(reg) info,
+      inlateout("eax") 116_i32 => ret, // __NR_sysinfo
+    );
+    i64::from(ret)
+  }
+}
+
+pub(super) unsafe fn sys_sched_getaffinity(
+  pid: i32,
+  mask_size: usize,
+  mask: *mut u8,
+) -> i32 {
+  unsafe {
+    let ret: i32;
+    core::arch::asm!(
+      "push ebx",
+      "mov ebx, {arg1:e}",
+      "int 0x80",
+      "pop ebx",
+      arg1 = in(reg) pid,
+      inlateout("eax") 242i32 => ret,  // __NR_sched_getaffinity
+      in("ecx") mask_size,
+      in("edx") mask,
+    );
+    ret
+  }
+}
+
+pub(super) unsafe fn sys_exit(code: i32) -> ! {
+  unsafe {
+    core::arch::asm!(
+      "mov ebx, {code:e}",
+      "int 0x80",
+      code = in(reg) code,
+      in("eax") 1i32,  // SYS_exit
+      options(noreturn)
+    );
+  }
+}

microfetch/src/main.rs

@@ -33,6 +33,23 @@ unsafe extern "C" fn _start() {
   );
 }
 
+#[cfg(target_arch = "x86")]
+#[unsafe(no_mangle)]
+#[unsafe(naked)]
+unsafe extern "C" fn _start() {
+  naked_asm!(
+    "mov eax, esp",    // save original sp (argc/argv)
+    "and esp, -16",    // align stack to 16 bytes
+    "sub esp, 12",     // leave room so that the one-arg push keeps alignment
+    "push eax",        // arg: initial stack pointer
+    "call {entry_rust}",
+    "mov ebx, eax",    // exit code -> first syscall arg
+    "mov eax, 1",      // SYS_exit
+    "int 0x80",
+    entry_rust = sym entry_rust,
+  );
+}
+
 #[cfg(target_arch = "aarch64")]
 #[unsafe(no_mangle)]
 #[unsafe(naked)]