arch: add mips32 support

.github/workflows/rust.yml

@@ -52,6 +52,11 @@ jobs:
           # powerpc uses experimental asm features
           - target: powerpc-unknown-linux-gnu
             toolchain: nightly
+          # mips is tier-3 and uses experimental asm features
+          - target: mips-unknown-linux-gnu
+            toolchain: nightly
+            components: rust-src
+            build_std: true
 
     steps:
     - name: "Checkout"
@@ -77,7 +82,7 @@ jobs:
         target: ${{ matrix.target }}
 
     - name: "Build"
-      run: cargo build --verbose --target ${{ matrix.target }} ${{ matrix.build_std && '-Z build-std=core,alloc,panic_abort' || '' }}
+      run: cargo build --verbose --target ${{ matrix.target }} ${{ matrix.build_std && '-Z build-std=core,alloc,panic_abort' || '' }} ${{ matrix.extra_args || '' }}
 
     # tier-3 targets have no prebuilt std and tests are arch-agnostic, so
     # run them against the host toolchain instead of the cross target.

crates/asm/src/lib.rs

@@ -7,7 +7,7 @@
 //!
 //! Supports `x86_64`, `aarch64`, `riscv64`, `loongarch64`, `s390x`,
 //! `powerpc64`, `arm` (armv7), `riscv32`, `sparc64`, `mips64`, `x86` (i686),
-//! `powerpc` (ppc32), and `sparc` (sparc32) architectures.
+//! `powerpc` (ppc32), `sparc` (sparc32), and `mips` (O32) architectures.
 
 #![no_std]
 #![cfg_attr(
@@ -16,7 +16,8 @@
     target_arch = "powerpc",
     target_arch = "sparc64",
     target_arch = "sparc",
-    target_arch = "mips64"
+    target_arch = "mips64",
+    target_arch = "mips"
   ),
   feature(asm_experimental_arch)
 )]
@@ -35,12 +36,13 @@
   target_arch = "mips64",
   target_arch = "x86",
   target_arch = "powerpc",
-  target_arch = "sparc"
+  target_arch = "sparc",
+  target_arch = "mips"
 )))]
 compile_error!(
   "Unsupported architecture: only x86_64, aarch64, riscv64, loongarch64, \
-   s390x, powerpc64, arm, riscv32, sparc64, mips64, x86, powerpc, and sparc \
-   are supported"
+   s390x, powerpc64, arm, riscv32, sparc64, mips64, x86, powerpc, sparc, and \
+   mips are supported"
 );
 
 // Per-arch syscall implementations live in their own module files.
@@ -83,6 +85,9 @@ mod arch;
 #[cfg(target_arch = "sparc")]
 #[path = "sparc.rs"]
 mod arch;
+#[cfg(target_arch = "mips")]
+#[path = "mips.rs"]
+mod arch;
 
 /// Copies `n` bytes from `src` to `dest`.
 ///
@@ -323,7 +328,8 @@ pub unsafe fn sys_uname(buf: *mut UtsNameBuf) -> i32 {
   target_arch = "x86",
   target_arch = "powerpc",
   target_arch = "sparc",
-  target_arch = "mips64"
+  target_arch = "mips64",
+  target_arch = "mips"
 )))]
 pub struct StatfsBuf {
   pub f_type:    i64,
@@ -389,6 +395,28 @@ pub struct StatfsBuf {
   pub _pad: [u32; 4],
 }
 
+/// mips (O32) uses `compat_statfs64`, same reordering with 32-bit words; see
+/// https://github.com/torvalds/linux/blob/v6.19/arch/mips/include/uapi/asm/statfs.h
+#[repr(C)]
+#[cfg(target_arch = "mips")]
+pub struct StatfsBuf {
+  pub f_type:    u32,
+  pub f_bsize:   u32,
+  pub f_frsize:  u32,
+  _pad:          u32,
+  pub f_blocks:  u64,
+  pub f_bfree:   u64,
+  pub f_files:   u64,
+  pub f_ffree:   u64,
+  pub f_bavail:  u64,
+  pub f_fsid:    [i32; 2],
+  pub f_namelen: u32,
+  pub f_flags:   u32,
+
+  #[allow(clippy::pub_underscore_fields, reason = "This is not a public API")]
+  pub _pad2: [u32; 5],
+}
+
 /// mips reorders fields; see
 /// https://github.com/torvalds/linux/blob/v6.19/arch/mips/include/uapi/asm/statfs.h
 #[repr(C)]
@@ -484,7 +512,8 @@ pub fn read_file_fast(path: &str, buffer: &mut [u8]) -> Result<usize, i32> {
   target_arch = "riscv32",
   target_arch = "x86",
   target_arch = "powerpc",
-  target_arch = "sparc"
+  target_arch = "sparc",
+  target_arch = "mips"
 )))]
 pub struct SysInfo {
   pub uptime:    i64,
@@ -514,7 +543,8 @@ pub struct SysInfo {
   target_arch = "riscv32",
   target_arch = "x86",
   target_arch = "powerpc",
-  target_arch = "sparc"
+  target_arch = "sparc",
+  target_arch = "mips"
 ))]
 pub struct SysInfo {
   pub uptime:    i32,

crates/asm/src/mips.rs

@@ -0,0 +1,196 @@
+//! Syscall implementations for `mips`.
+
+use super::{StatfsBuf, SysInfo, UtsNameBuf};
+
+pub(super) unsafe fn sys_open(path: *const u8, flags: i32) -> i32 {
+  unsafe {
+    let ret: i32;
+    core::arch::asm!(
+      "syscall",
+      "beqz $7, 1f",
+      "nop",
+      "subu $2, $0, $2",
+      "1:",
+      inlateout("$2") 4000i32 + 5 => ret,  // SYS_open
+      in("$4") path,
+      in("$5") flags,
+      in("$6") 0i32,  // mode
+      lateout("$7") _,
+      lateout("$8") _, lateout("$9") _, lateout("$10") _, lateout("$11") _,
+      lateout("$12") _, lateout("$13") _, lateout("$14") _, lateout("$15") _,
+      lateout("$24") _, lateout("$25") _,
+      options(nostack)
+    );
+    ret
+  }
+}
+
+pub(super) unsafe fn sys_read(fd: i32, buf: *mut u8, count: usize) -> isize {
+  unsafe {
+    let ret: i32;
+    core::arch::asm!(
+      "syscall",
+      "beqz $7, 1f",
+      "nop",
+      "subu $2, $0, $2",
+      "1:",
+      inlateout("$2") 4000i32 + 3 => ret,  // SYS_read
+      in("$4") fd,
+      in("$5") buf,
+      in("$6") count,
+      lateout("$7") _,
+      lateout("$8") _, lateout("$9") _, lateout("$10") _, lateout("$11") _,
+      lateout("$12") _, lateout("$13") _, lateout("$14") _, lateout("$15") _,
+      lateout("$24") _, lateout("$25") _,
+      options(nostack)
+    );
+    ret as isize
+  }
+}
+
+pub(super) unsafe fn sys_write(fd: i32, buf: *const u8, count: usize) -> isize {
+  unsafe {
+    let ret: i32;
+    core::arch::asm!(
+      "syscall",
+      "beqz $7, 1f",
+      "nop",
+      "subu $2, $0, $2",
+      "1:",
+      inlateout("$2") 4000i32 + 4 => ret,  // SYS_write
+      in("$4") fd,
+      in("$5") buf,
+      in("$6") count,
+      lateout("$7") _,
+      lateout("$8") _, lateout("$9") _, lateout("$10") _, lateout("$11") _,
+      lateout("$12") _, lateout("$13") _, lateout("$14") _, lateout("$15") _,
+      lateout("$24") _, lateout("$25") _,
+      options(nostack)
+    );
+    ret as isize
+  }
+}
+
+pub(super) unsafe fn sys_close(fd: i32) -> i32 {
+  unsafe {
+    let ret: i32;
+    core::arch::asm!(
+      "syscall",
+      "beqz $7, 1f",
+      "nop",
+      "subu $2, $0, $2",
+      "1:",
+      inlateout("$2") 4000i32 + 6 => ret,  // SYS_close
+      in("$4") fd,
+      lateout("$7") _,
+      lateout("$8") _, lateout("$9") _, lateout("$10") _, lateout("$11") _,
+      lateout("$12") _, lateout("$13") _, lateout("$14") _, lateout("$15") _,
+      lateout("$24") _, lateout("$25") _,
+      options(nostack)
+    );
+    ret
+  }
+}
+
+pub(super) unsafe fn sys_uname(buf: *mut UtsNameBuf) -> i32 {
+  unsafe {
+    let ret: i32;
+    core::arch::asm!(
+      "syscall",
+      "beqz $7, 1f",
+      "nop",
+      "subu $2, $0, $2",
+      "1:",
+      inlateout("$2") 4000i32 + 122 => ret,  // SYS_newuname
+      in("$4") buf,
+      lateout("$7") _,
+      lateout("$8") _, lateout("$9") _, lateout("$10") _, lateout("$11") _,
+      lateout("$12") _, lateout("$13") _, lateout("$14") _, lateout("$15") _,
+      lateout("$24") _, lateout("$25") _,
+      options(nostack)
+    );
+    ret
+  }
+}
+
+pub(super) unsafe fn sys_statfs(path: *const u8, buf: *mut StatfsBuf) -> i32 {
+  unsafe {
+    let ret: i32;
+    core::arch::asm!(
+      "syscall",
+      "beqz $7, 1f",
+      "nop",
+      "subu $2, $0, $2",
+      "1:",
+      inlateout("$2") 4000i32 + 255 => ret,  // SYS_statfs64
+      in("$4") path,
+      in("$5") core::mem::size_of::<StatfsBuf>(),
+      in("$6") buf,
+      lateout("$7") _,
+      lateout("$8") _, lateout("$9") _, lateout("$10") _, lateout("$11") _,
+      lateout("$12") _, lateout("$13") _, lateout("$14") _, lateout("$15") _,
+      lateout("$24") _, lateout("$25") _,
+      options(nostack)
+    );
+    ret
+  }
+}
+
+pub(super) unsafe fn sys_sysinfo(info: *mut SysInfo) -> i64 {
+  unsafe {
+    let ret: i32;
+    core::arch::asm!(
+      "syscall",
+      "beqz $7, 1f",
+      "nop",
+      "subu $2, $0, $2",
+      "1:",
+      inlateout("$2") 4000_i32 + 116 => ret,  // __NR_sysinfo
+      in("$4") info,
+      lateout("$7") _,
+      lateout("$8") _, lateout("$9") _, lateout("$10") _, lateout("$11") _,
+      lateout("$12") _, lateout("$13") _, lateout("$14") _, lateout("$15") _,
+      lateout("$24") _, lateout("$25") _,
+      options(nostack)
+    );
+    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!(
+      "syscall",
+      "beqz $7, 1f",
+      "nop",
+      "subu $2, $0, $2",
+      "1:",
+      inlateout("$2") 4000i32 + 240 => ret,  // __NR_sched_getaffinity
+      in("$4") pid,
+      in("$5") mask_size,
+      in("$6") mask,
+      lateout("$7") _,
+      lateout("$8") _, lateout("$9") _, lateout("$10") _, lateout("$11") _,
+      lateout("$12") _, lateout("$13") _, lateout("$14") _, lateout("$15") _,
+      lateout("$24") _, lateout("$25") _,
+      options(nostack)
+    );
+    ret
+  }
+}
+
+pub(super) unsafe fn sys_exit(code: i32) -> ! {
+  unsafe {
+    core::arch::asm!(
+      "syscall",
+      in("$2") 4000i32 + 1,  // SYS_exit
+      in("$4") code,
+      options(noreturn, nostack)
+    );
+  }
+}

microfetch/src/main.rs

@@ -6,7 +6,8 @@
     target_arch = "powerpc",
     target_arch = "sparc64",
     target_arch = "sparc",
-    target_arch = "mips64"
+    target_arch = "mips64",
+    target_arch = "mips"
   ),
   feature(asm_experimental_arch)
 )]
@@ -280,6 +281,22 @@ extern "C" fn __atomic_store_1(ptr: *mut u8, val: u8, _order: i32) {
   unsafe { core::ptr::write_volatile(ptr, val) }
 }
 
+#[cfg(target_arch = "mips")]
+#[unsafe(no_mangle)]
+#[unsafe(naked)]
+unsafe extern "C" fn _start() {
+  naked_asm!(
+    "move $a0, $sp",       // first arg = original sp (argc/argv)
+    "addiu $sp, $sp, -24", // reserve 16-byte O32 shadow space + align
+    "jal {entry_rust}",
+    "nop",                 // delay slot
+    "move $a0, $v0",       // exit code = entry_rust return value
+    "li $v0, 4001",        // SYS_exit (4000 + 1)
+    "syscall",
+    entry_rust = sym entry_rust,
+  );
+}
+
 // Global allocator
 #[global_allocator]
 static ALLOCATOR: BumpAllocator = BumpAllocator::new();