std: add support for armv7a-vex-v5 target

Co-authored-by: Lewis McClelland <lewis@lewismcclelland.me>

compiler/rustc_target/src/spec/targets/armv7a_vex_v5.rs

@@ -34,7 +34,7 @@ pub(crate) fn target() -> Target {
             description: Some("ARMv7-A Cortex-A9 VEX V5 Brain".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: Some(false),
+            std: Some(true),
         },
         pointer_width: 32,
         data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".into(),

library/Cargo.lock

@@ -326,6 +326,7 @@ dependencies = [
  "rustc-demangle",
  "std_detect",
  "unwind",
+ "vex-sdk",
  "wasi 0.11.1+wasi-snapshot-preview1",
  "wasi 0.14.4+wasi-0.2.4",
  "windows-targets 0.0.0",
@@ -379,6 +380,15 @@ dependencies = [
  "rustc-std-workspace-core",
 ]
 
+[[package]]
+name = "vex-sdk"
+version = "0.27.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "89f74fce61d7a7ba1589da9634c6305a72befb7cc9150c1f872d87d8060f32b9"
+dependencies = [
+ "rustc-std-workspace-core",
+]
+
 [[package]]
 name = "wasi"
 version = "0.11.1+wasi-snapshot-preview1"

library/std/Cargo.toml

@@ -62,7 +62,7 @@ path = "../windows_targets"
 rand = { version = "0.9.0", default-features = false, features = ["alloc"] }
 rand_xorshift = "0.4.0"
 
-[target.'cfg(any(all(target_family = "wasm", target_os = "unknown"), target_os = "xous", all(target_vendor = "fortanix", target_env = "sgx")))'.dependencies]
+[target.'cfg(any(all(target_family = "wasm", target_os = "unknown"), target_os = "xous", target_os = "vexos", all(target_vendor = "fortanix", target_env = "sgx")))'.dependencies]
 dlmalloc = { version = "0.2.10", features = ['rustc-dep-of-std'] }
 
 [target.x86_64-fortanix-unknown-sgx.dependencies]
@@ -89,6 +89,11 @@ wasip2 = { version = '0.14.4', features = [
 r-efi = { version = "5.2.0", features = ['rustc-dep-of-std'] }
 r-efi-alloc = { version = "2.0.0", features = ['rustc-dep-of-std'] }
 
+[target.'cfg(target_os = "vexos")'.dependencies]
+vex-sdk = { version = "0.27.0", features = [
+    'rustc-dep-of-std',
+], default-features = false }
+
 [features]
 backtrace = [
     'addr2line/rustc-dep-of-std',

library/std/build.rs

@@ -52,6 +52,7 @@ fn main() {
         || target_os == "rtems"
         || target_os == "nuttx"
         || target_os == "cygwin"
+        || target_os == "vexos"
 
         // See src/bootstrap/src/core/build_steps/synthetic_targets.rs
         || env::var("RUSTC_BOOTSTRAP_SYNTHETIC_TARGET").is_ok()

library/std/src/env.rs

@@ -1098,6 +1098,7 @@ pub mod consts {
     /// * `"redox"`
     /// * `"solaris"`
     /// * `"solid_asp3`
+    /// * `"vexos"`
     /// * `"vita"`
     /// * `"vxworks"`
     /// * `"xous"`
@@ -1148,6 +1149,7 @@ pub mod consts {
     ///
     /// <details><summary>Full list of possible values</summary>
     ///
+    /// * `"bin"`
     /// * `"exe"`
     /// * `"efi"`
     /// * `"js"`

library/std/src/sys/alloc/mod.rs

@@ -92,6 +92,9 @@ cfg_select! {
     target_os = "uefi" => {
         mod uefi;
     }
+    target_os = "vexos" => {
+        mod vexos;
+    }
     target_family = "wasm" => {
         mod wasm;
     }

library/std/src/sys/alloc/vexos.rs

@@ -0,0 +1,96 @@
+// FIXME(static_mut_refs): Do not allow `static_mut_refs` lint
+#![allow(static_mut_refs)]
+
+use crate::alloc::{GlobalAlloc, Layout, System};
+use crate::ptr;
+use crate::sync::atomic::{AtomicBool, Ordering};
+
+// Symbols for heap section boundaries defined in the target's linkerscript
+unsafe extern "C" {
+    static mut __heap_start: u8;
+    static mut __heap_end: u8;
+}
+
+static mut DLMALLOC: dlmalloc::Dlmalloc<Vexos> = dlmalloc::Dlmalloc::new_with_allocator(Vexos);
+
+struct Vexos;
+
+unsafe impl dlmalloc::Allocator for Vexos {
+    /// Allocs system resources
+    fn alloc(&self, _size: usize) -> (*mut u8, usize, u32) {
+        static INIT: AtomicBool = AtomicBool::new(false);
+
+        if !INIT.swap(true, Ordering::Relaxed) {
+            // This target has no growable heap, as user memory has a fixed
+            // size/location and VEXos does not manage allocation for us.
+            unsafe {
+                (
+                    (&raw mut __heap_start).cast::<u8>(),
+                    (&raw const __heap_end).offset_from_unsigned(&raw const __heap_start),
+                    0,
+                )
+            }
+        } else {
+            (ptr::null_mut(), 0, 0)
+        }
+    }
+
+    fn remap(&self, _ptr: *mut u8, _oldsize: usize, _newsize: usize, _can_move: bool) -> *mut u8 {
+        ptr::null_mut()
+    }
+
+    fn free_part(&self, _ptr: *mut u8, _oldsize: usize, _newsize: usize) -> bool {
+        false
+    }
+
+    fn free(&self, _ptr: *mut u8, _size: usize) -> bool {
+        return false;
+    }
+
+    fn can_release_part(&self, _flags: u32) -> bool {
+        false
+    }
+
+    fn allocates_zeros(&self) -> bool {
+        false
+    }
+
+    fn page_size(&self) -> usize {
+        0x1000
+    }
+}
+
+#[stable(feature = "alloc_system_type", since = "1.28.0")]
+unsafe impl GlobalAlloc for System {
+    #[inline]
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        // SAFETY: DLMALLOC access is guaranteed to be safe because we are a single-threaded target, which
+        // guarantees unique and non-reentrant access to the allocator. As such, no allocator lock is used.
+        // Calling malloc() is safe because preconditions on this function match the trait method preconditions.
+        unsafe { DLMALLOC.malloc(layout.size(), layout.align()) }
+    }
+
+    #[inline]
+    unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
+        // SAFETY: DLMALLOC access is guaranteed to be safe because we are a single-threaded target, which
+        // guarantees unique and non-reentrant access to the allocator. As such, no allocator lock is used.
+        // Calling calloc() is safe because preconditions on this function match the trait method preconditions.
+        unsafe { DLMALLOC.calloc(layout.size(), layout.align()) }
+    }
+
+    #[inline]
+    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
+        // SAFETY: DLMALLOC access is guaranteed to be safe because we are a single-threaded target, which
+        // guarantees unique and non-reentrant access to the allocator. As such, no allocator lock is used.
+        // Calling free() is safe because preconditions on this function match the trait method preconditions.
+        unsafe { DLMALLOC.free(ptr, layout.size(), layout.align()) }
+    }
+
+    #[inline]
+    unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
+        // SAFETY: DLMALLOC access is guaranteed to be safe because we are a single-threaded target, which
+        // guarantees unique and non-reentrant access to the allocator. As such, no allocator lock is used.
+        // Calling realloc() is safe because preconditions on this function match the trait method preconditions.
+        unsafe { DLMALLOC.realloc(ptr, layout.size(), layout.align(), new_size) }
+    }
+}

library/std/src/sys/env_consts.rs

@@ -323,6 +323,17 @@ pub mod os {
     pub const EXE_EXTENSION: &str = "efi";
 }
 
+#[cfg(target_os = "vexos")]
+pub mod os {
+    pub const FAMILY: &str = "";
+    pub const OS: &str = "vexos";
+    pub const DLL_PREFIX: &str = "";
+    pub const DLL_SUFFIX: &str = "";
+    pub const DLL_EXTENSION: &str = "";
+    pub const EXE_SUFFIX: &str = ".bin";
+    pub const EXE_EXTENSION: &str = "bin";
+}
+
 #[cfg(target_os = "visionos")]
 pub mod os {
     pub const FAMILY: &str = "unix";

library/std/src/sys/fs/mod.rs

@@ -35,6 +35,10 @@ cfg_select! {
         mod uefi;
         use uefi as imp;
     }
+    target_os = "vexos" => {
+        mod vexos;
+        use vexos as imp;
+    }
     target_os = "wasi" => {
         mod wasi;
         use wasi as imp;