Allow compiling debug-builtins in no_std environment to enable gdb jit

- Make jit-debug crate #![no_std] when perf_jitdebug is not enabled
- Make gdb_jit_int module build in no_std environment
- Use std when perf_jitdebug is enabled because the perf_jitdebug module
  does not run in no_std environment
- Split debug-builtins feature into debug-builtins and perf-builtins to
  individually toggle:
    - the no_std gdb_jit_int module by using debug-builtins
    - the std perf_jitdebug module using perf-builtins.
  NOTE: They can be both enabled, but it won't support no_std.

Signed-off-by: Doru Blânzeanu <dblnz@pm.me>

Author: dblnz

Cargo.lock

@@ -460,6 +460,7 @@ default = [
   "coredump",
   "addr2line",
   "debug-builtins",
+  "perf-builtins",
   "component-model",
   "threads",
   "gc",
@@ -519,6 +520,7 @@ profiling = ["wasmtime/profiling", "wasmtime/call-hook"]
 coredump = ["wasmtime-cli-flags/coredump"]
 addr2line = ["wasmtime/addr2line"]
 debug-builtins = ["wasmtime/debug-builtins"]
+perf-builtins = ["wasmtime/perf-builtins"]
 threads = ["wasmtime-cli-flags/threads"]
 gc = ["wasmtime-cli-flags/gc", "wasmtime/gc"]
 gc-drc = ["gc", "wasmtime/gc-drc", "wasmtime-cli-flags/gc-drc"]

Cargo.toml

@@ -20,6 +20,7 @@ wasmtime-versioned-export-macros = { workspace = true }
 
 [dependencies]
 object = { workspace = true, optional = true }
+spin = "0.10.0"
 wasmtime-versioned-export-macros = { workspace = true }
 
 [target.'cfg(target_os = "linux")'.dependencies]

crates/jit-debug/Cargo.toml

@@ -2,9 +2,11 @@
 //! the __jit_debug_register_code() and __jit_debug_descriptor to register
 //! or unregister generated object images with debuggers.
 
-use std::pin::Pin;
-use std::ptr;
-use std::sync::Mutex;
+use alloc::boxed::Box;
+use alloc::vec::Vec;
+use core::pin::Pin;
+use core::ptr;
+use spin::mutex::Mutex;
 use wasmtime_versioned_export_macros::versioned_link;
 
 #[repr(C)]
@@ -87,7 +89,7 @@ unsafe impl Sync for GdbJitImageRegistration {}
 
 unsafe fn register_gdb_jit_image(entry: *mut JITCodeEntry) {
     unsafe {
-        let _lock = GDB_REGISTRATION.lock().unwrap();
+        let _lock = GDB_REGISTRATION.lock();
         let desc = &mut *wasmtime_jit_debug_descriptor();
 
         // Add it to the linked list in the JIT descriptor.
@@ -109,7 +111,7 @@ unsafe fn register_gdb_jit_image(entry: *mut JITCodeEntry) {
 
 unsafe fn unregister_gdb_jit_image(entry: *mut JITCodeEntry) {
     unsafe {
-        let _lock = GDB_REGISTRATION.lock().unwrap();
+        let _lock = GDB_REGISTRATION.lock();
         let desc = &mut *wasmtime_jit_debug_descriptor();
 
         // Remove the code entry corresponding to the code from the linked list.

crates/jit-debug/src/gdb_jit_int.rs

@@ -4,6 +4,12 @@
 //! > you're interested in using this feel free to file an issue on the
 //! > Wasmtime repository to start a discussion about doing so, but otherwise
 //! > be aware that your usage of this crate is not supported.
+#![no_std]
+
+#[cfg(feature = "gdb_jit_int")]
+extern crate alloc;
+#[cfg(all(feature = "perf_jitdump", target_os = "linux"))]
+extern crate std;
 
 #[cfg(feature = "gdb_jit_int")]
 pub mod gdb_jit_int;

crates/jit-debug/src/lib.rs

@@ -16,6 +16,8 @@ use std::io;
 use std::io::Write;
 use std::path::Path;
 use std::ptr;
+use std::string::String;
+use std::vec::Vec;
 use std::{mem, process};
 
 /// Defines jitdump record types

crates/jit-debug/src/perf_jitdump.rs

@@ -139,6 +139,7 @@ default = [
   'addr2line',
   'coredump',
   'debug-builtins',
+  'perf-builtins',
   'runtime',
   'component-model',
   'threads',
@@ -243,7 +244,8 @@ coredump = ["dep:wasm-encoder", "runtime", "std"]
 
 # Export some symbols from the final binary to assist in debugging
 # Cranelift-generated code with native debuggers like GDB and LLDB.
-debug-builtins = ["dep:wasmtime-jit-debug", "std"]
+debug-builtins = ["wasmtime-jit-debug/gdb_jit_int"]
+perf-builtins = ["wasmtime-jit-debug/perf_jitdump"]
 
 # Enable support for executing compiled Wasm modules.
 runtime = [

crates/wasmtime/Cargo.toml

@@ -27,10 +27,10 @@ fn main() {
     custom_cfg("has_virtual_memory", has_virtual_memory);
     custom_cfg("has_host_compiler_backend", has_host_compiler_backend);
 
-    // If this OS isn't supported or if Cranelift doesn't support the host then
-    // there's no need to build these helpers.
+    // If this OS isn't supported or if Cranelift doesn't support the host or
+    // if no debug-builtins enabled then there's no need to build these helpers.
     #[cfg(feature = "runtime")]
-    if supported_os && has_host_compiler_backend {
+    if (supported_os && has_host_compiler_backend) || cfg!(feature = "debug-builtins") {
         build_c_helpers();
     }
 

crates/wasmtime/build.rs

@@ -109,7 +109,7 @@ impl Engine {
             #[cfg(has_native_signals)]
             crate::runtime::vm::init_traps(config.macos_use_mach_ports);
             if !cfg!(miri) {
-                #[cfg(all(has_host_compiler_backend, feature = "debug-builtins"))]
+                #[cfg(feature = "debug-builtins")]
                 crate::runtime::vm::debug_builtins::init();
             }
         }

crates/wasmtime/src/engine.rs

@@ -13,7 +13,7 @@ static mut VMCTX_AND_MEMORY: (NonNull<VMContext>, usize) = (NonNull::dangling(),
 
 #[versioned_export]
 pub unsafe extern "C" fn resolve_vmctx_memory_ptr(p: *const u32) -> *const u8 {
-    let ptr = std::ptr::read(p);
+    let ptr = core::ptr::read(p);
     assert!(
         VMCTX_AND_MEMORY.0 != NonNull::dangling(),
         "must call `__vmctx->set()` before resolving Wasm pointers"