Auto merge of #135651 - arjunr2:master, r=davidtwco

Support for `wasm32-wali-linux-musl` Tier-3 target

Adding a new target -- `wasm32-wali-linux-musl` -- to the compiler can target the [WebAssembly Linux Interface](https://github.com/arjunr2/WALI) according to MCP rust-lang/compiler-team#797
Preliminary support involves minimal changes, primarily

* A new target spec for `wasm32_wali_linux_musl` that bridges linux options with supported wasm options. Right now, since there is no canonical Linux ABI for Wasm, we use `wali` in the vendor field, but this can be migrated in future version.
* Dependency patches to the following crates are required and these crates can be updated to bring target support:
  - **stdarch** rust-lang/stdarch#1702
  - **libc** rust-lang/libc#4244
  - **cc** rust-lang/cc-rs#1373
* Minimal additions for FFI support

cc `@tgross35` for libc-related changes

Tier-3 policy:
> A tier 3 target must have a designated developer or developers (the "target maintainers") on record to be CCed when issues arise regarding the target. (The mechanism to track and CC such developers may evolve over time.)

I will take responsibility for maintaining this target as well as issues

> Targets must use naming consistent with any existing targets; for instance, a target for the same CPU or OS as an existing Rust target should use the same name for that CPU or OS. Targets should normally use the same names and naming conventions as used elsewhere in the broader ecosystem beyond Rust (such as in other toolchains), unless they have a very good reason to diverge. Changing the name of a target can be highly disruptive, especially once the target reaches a higher tier, so getting the name right is important even for a tier 3 target.

The target name is consistent with naming patterns from currently supported targets for arch (wasm32), OS, (linux) and env (musl)

> Target names should not introduce undue confusion or ambiguity unless absolutely necessary to maintain ecosystem compatibility. For example, if the name of the target makes people extremely likely to form incorrect beliefs about what it targets, the name should be changed or augmented to disambiguate it.

No naming confusion is introduced.

> If possible, use only letters, numbers, dashes and underscores for the name. Periods (.) are known to cause issues in Cargo.

Compliant

> Tier 3 targets may have unusual requirements to build or use, but must not create legal issues or impose onerous legal terms for the Rust project or for Rust developers or users.

It's fully open source

> The target must not introduce license incompatibilities. Anything added to the Rust repository must be under the standard Rust license (MIT OR Apache-2.0).

Noted

> The target must not cause the Rust tools or libraries built for any other host (even when supporting cross-compilation to the target) to depend on any new dependency less permissive than the Rust licensing policy. This applies whether the dependency is a Rust crate that would require adding new license exceptions (as specified by the tidy tool in the rust-lang/rust repository), or whether the dependency is a native library or binary. In other words, the introduction of the target must not cause a user installing or running a version of Rust or the Rust tools to be subject to any new license requirements.

Compliant

> Compiling, linking, and emitting functional binaries, libraries, or other code for the target (whether hosted on the target itself or cross-compiling from another target) must not depend on proprietary (non-FOSS) libraries. Host tools built for the target itself may depend on the ordinary runtime libraries supplied by the platform and commonly used by other applications built for the target, but those libraries must not be required for code generation for the target; cross-compilation to the target must not require such libraries at all. For instance, rustc built for the target may depend on a common proprietary C runtime library or console output library, but must not depend on a proprietary code generation library or code optimization library. Rust's license permits such combinations, but the Rust project has no interest in maintaining such combinations within the scope of Rust itself, even at tier 3.

All tools are open-source

> "onerous" here is an intentionally subjective term. At a minimum, "onerous" legal/licensing terms include but are not limited to: non-disclosure requirements, non-compete requirements, contributor license agreements (CLAs) or equivalent, "non-commercial"/"research-only"/etc terms, requirements conditional on the employer or employment of any particular Rust developers, revocable terms, any requirements that create liability for the Rust project or its developers or users, or any requirements that adversely affect the livelihood or prospects of the Rust project or its developers or users.

No terms present

> Neither this policy nor any decisions made regarding targets shall create any binding agreement or estoppel by any party. If any member of an approving Rust team serves as one of the maintainers of a target, or has any legal or employment requirement (explicit or implicit) that might affect their decisions regarding a target, they must recuse themselves from any approval decisions regarding the target's tier status, though they may otherwise participate in discussions.
This requirement does not prevent part or all of this policy from being cited in an explicit contract or work agreement (e.g. to implement or maintain support for a target). This requirement exists to ensure that a developer or team responsible for reviewing and approving a target does not face any legal threats or obligations that would prevent them from freely exercising their judgment in such approval, even if such judgment involves subjective matters or goes beyond the letter of these requirements.

I am not a reviewer

> Tier 3 targets should attempt to implement as much of the standard libraries as possible and appropriate (core for most targets, alloc for targets that can support dynamic memory allocation, std for targets with an operating system or equivalent layer of system-provided functionality), but may leave some code unimplemented (either unavailable or stubbed out as appropriate), whether because the target makes it impossible to implement or challenging to implement. The authors of pull requests are not obligated to avoid calling any portions of the standard library on the basis of a tier 3 target not implementing those portions.

This target supports the full standard library with appropriate configuration stubs where necessary (however, similar to all existing wasm32 targets, it excludes dynamic linking or hardware-specific features)

> The target must provide documentation for the Rust community explaining how to build for the target, using cross-compilation if possible. If the target supports running binaries, or running tests (even if they do not pass), the documentation must explain how to run such binaries or tests for the target, using emulation if possible or dedicated hardware if necessary.

Preliminary documentation is provided at https://github.com/arjunr2/WALI. Further detailed docs (if necessary) can be added once this PR lands

> Tier 3 targets must not impose burden on the authors of pull requests, or other developers in the community, to maintain the target. In particular, do not post comments (automated or manual) on a PR that derail or suggest a block on the PR based on a tier 3 target. Do not send automated messages or notifications (via any medium, including via `@)` to a PR author or others involved with a PR regarding a tier 3 target, unless they have opted into such messages.
Backlinks such as those generated by the issue/PR tracker when linking to an issue or PR are not considered a violation of this policy, within reason. However, such messages (even on a separate repository) must not generate notifications to anyone involved with a PR who has not requested such notifications.

Understood

> Patches adding or updating tier 3 targets must not break any existing tier 2 or tier 1 target, and must not knowingly break another tier 3 target without approval of either the compiler team or the maintainers of the other tier 3 target.
In particular, this may come up when working on closely related targets, such as variations of the same architecture with different features. Avoid introducing unconditional uses of features that another variation of the target may not have; use conditional compilation or runtime detection, as appropriate, to let each target run code supported by that target.

To the best of my knowledge, it does not break any existing target in the ecosystem -- only minimal configuration-specific additions were made to support the target.

> Tier 3 targets must be able to produce assembly using at least one of rustc's supported backends from any host target. (Having support in a fork of the backend is not sufficient, it must be upstream.)

We can upstream LLVM target support

14 files changed, 352 insertions, 20 deletions

diff --git a/compiler/rustc_target/src/spec/base/linux_wasm.rs b/compiler/rustc_target/src/spec/base/linux_wasm.rs
new file mode 100644
index 00000000000..a8c137c22a9
--- /dev/null
+++ b/compiler/rustc_target/src/spec/base/linux_wasm.rs
@@ -0,0 +1,159 @@
+//! This target is a confluence of Linux and Wasm models, inheriting most
+//! aspects from their respective base targets
+
+use crate::spec::{
+    Cc, LinkSelfContainedDefault, LinkerFlavor, PanicStrategy, RelocModel, TargetOptions, TlsModel,
+    add_link_args, crt_objects, cvs,
+};
+
+pub(crate) fn opts() -> TargetOptions {
+    macro_rules! args {
+        ($prefix:literal) => {
+            &[
+                // By default LLD only gives us one page of stack (64k) which is a
+                // little small. Default to a larger stack closer to other PC platforms
+                // (1MB) and users can always inject their own link-args to override this.
+                concat!($prefix, "-z"),
+                concat!($prefix, "stack-size=1048576"),
+                // By default LLD's memory layout is:
+                //
+                // 1. First, a blank page
+                // 2. Next, all static data
+                // 3. Finally, the main stack (which grows down)
+                //
+                // This has the unfortunate consequence that on stack overflows you
+                // corrupt static data and can cause some exceedingly weird bugs. To
+                // help detect this a little sooner we instead request that the stack is
+                // placed before static data.
+                //
+                // This means that we'll generate slightly larger binaries as references
+                // to static data will take more bytes in the ULEB128 encoding, but
+                // stack overflow will be guaranteed to trap as it underflows instead of
+                // corrupting static data.
+                concat!($prefix, "--stack-first"),
+                // FIXME we probably shouldn't pass this but instead pass an explicit list
+                // of symbols we'll allow to be undefined. We don't currently have a
+                // mechanism of knowing, however, which symbols are intended to be imported
+                // from the environment and which are intended to be imported from other
+                // objects linked elsewhere. This is a coarse approximation but is sure to
+                // hide some bugs and frustrate someone at some point, so we should ideally
+                // work towards a world where we can explicitly list symbols that are
+                // supposed to be imported and have all other symbols generate errors if
+                // they remain undefined.
+                concat!($prefix, "--allow-undefined"),
+                // LLD only implements C++-like demangling, which doesn't match our own
+                // mangling scheme. Tell LLD to not demangle anything and leave it up to
+                // us to demangle these symbols later. Currently rustc does not perform
+                // further demangling, but tools like twiggy and wasm-bindgen are intended
+                // to do so.
+                concat!($prefix, "--no-demangle"),
+            ]
+        };
+    }
+
+    let mut pre_link_args = TargetOptions::link_args(LinkerFlavor::WasmLld(Cc::No), args!(""));
+    add_link_args(&mut pre_link_args, LinkerFlavor::WasmLld(Cc::Yes), args!("-Wl,"));
+
+    TargetOptions {
+        is_like_wasm: true,
+        families: cvs!["wasm", "unix"],
+        os: "linux".into(),
+        env: "musl".into(),
+
+        // we allow dynamic linking, but only cdylibs. Basically we allow a
+        // final library artifact that exports some symbols (a wasm module) but
+        // we don't allow intermediate `dylib` crate types
+        dynamic_linking: true,
+        only_cdylib: true,
+
+        // relatively self-explanatory!
+        exe_suffix: ".wasm".into(),
+        dll_prefix: "".into(),
+        dll_suffix: ".wasm".into(),
+        eh_frame_header: false,
+
+        max_atomic_width: Some(64),
+
+        // Unwinding doesn't work right now, so the whole target unconditionally
+        // defaults to panic=abort. Note that this is guaranteed to change in
+        // the future once unwinding is implemented. Don't rely on this as we're
+        // basically guaranteed to change it once WebAssembly supports
+        // exceptions.
+        panic_strategy: PanicStrategy::Abort,
+
+        // Symbol visibility takes care of this for the WebAssembly.
+        // Additionally the only known linker, LLD, doesn't support the script
+        // arguments just yet
+        limit_rdylib_exports: false,
+
+        // we use the LLD shipped with the Rust toolchain by default
+        linker: Some("rust-lld".into()),
+        linker_flavor: LinkerFlavor::WasmLld(Cc::No),
+
+        pre_link_args,
+
+        // FIXME: Figure out cases in which WASM needs to link with a native toolchain.
+        //
+        // rust-lang/rust#104137: cannot blindly remove this without putting in
+        // some other way to compensate for lack of `-nostartfiles` in linker
+        // invocation.
+        link_self_contained: LinkSelfContainedDefault::True,
+        pre_link_objects_self_contained: crt_objects::pre_wasi_self_contained(),
+        post_link_objects_self_contained: crt_objects::post_wasi_self_contained(),
+
+        // This has no effect in LLVM 8 or prior, but in LLVM 9 and later when
+        // PIC code is implemented this has quite a drastic effect if it stays
+        // at the default, `pic`. In an effort to keep wasm binaries as minimal
+        // as possible we're defaulting to `static` for now, but the hope is
+        // that eventually we can ship a `pic`-compatible standard library which
+        // works with `static` as well (or works with some method of generating
+        // non-relative calls and such later on).
+        relocation_model: RelocModel::Static,
+
+        // When the atomics feature is activated then these two keys matter,
+        // otherwise they're basically ignored by the standard library. In this
+        // mode, however, the `#[thread_local]` attribute works (i.e.
+        // `has_thread_local`) and we need to get it to work by specifying
+        // `local-exec` as that's all that's implemented in LLVM today for wasm.
+        has_thread_local: true,
+        tls_model: TlsModel::LocalExec,
+
+        // Supporting Linux requires multithreading supported by Wasm's thread
+        // proposal
+        singlethread: false,
+
+        // gdb scripts don't work on wasm blobs
+        emit_debug_gdb_scripts: false,
+
+        // There's more discussion of this at
+        // https://bugs.llvm.org/show_bug.cgi?id=52442 but the general result is
+        // that this isn't useful for wasm and has tricky issues with
+        // representation, so this is disabled.
+        generate_arange_section: false,
+
+        // Right now this is a bit of a workaround but we're currently saying that
+        // the target by default has a static crt which we're taking as a signal
+        // for "use the bundled crt". If that's turned off then the system's crt
+        // will be used, but this means that default usage of this target doesn't
+        // need an external compiler but it's still interoperable with an external
+        // compiler if configured correctly.
+        crt_static_default: true,
+        crt_static_respected: true,
+
+        // Allow `+crt-static` to create a "cdylib" output which is just a wasm file
+        // without a main function.
+        crt_static_allows_dylibs: true,
+
+        // Wasm start ignores arguments -- relies on API call from interface.
+        main_needs_argc_argv: false,
+
+        // Wasm toolchains mangle the name of "main" to distinguish between different
+        // signatures.
+        entry_name: "__main_void".into(),
+
+        // Wasm Feature flags for supporting Linux
+        features: "+atomics,+bulk-memory,+mutable-globals,+sign-ext".into(),
+
+        ..Default::default()
+    }
+}
diff --git a/compiler/rustc_target/src/spec/base/mod.rs b/compiler/rustc_target/src/spec/base/mod.rs
index 6f88be5d37f..e8fdc871785 100644
--- a/compiler/rustc_target/src/spec/base/mod.rs
+++ b/compiler/rustc_target/src/spec/base/mod.rs
@@ -18,6 +18,7 @@ pub(crate) mod linux_gnu;
 pub(crate) mod linux_musl;
 pub(crate) mod linux_ohos;
 pub(crate) mod linux_uclibc;
+pub(crate) mod linux_wasm;
 pub(crate) mod msvc;
 pub(crate) mod netbsd;
 pub(crate) mod nto_qnx;
diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs
index 15936c731ea..1887134c575 100644
--- a/compiler/rustc_target/src/spec/mod.rs
+++ b/compiler/rustc_target/src/spec/mod.rs
@@ -1924,6 +1924,7 @@ supported_targets! {
     ("wasm32-wasip1", wasm32_wasip1),
     ("wasm32-wasip2", wasm32_wasip2),
     ("wasm32-wasip1-threads", wasm32_wasip1_threads),
+    ("wasm32-wali-linux-musl", wasm32_wali_linux_musl),
     ("wasm64-unknown-unknown", wasm64_unknown_unknown),
 
     ("thumbv6m-none-eabi", thumbv6m_none_eabi),
diff --git a/compiler/rustc_target/src/spec/targets/wasm32_wali_linux_musl.rs b/compiler/rustc_target/src/spec/targets/wasm32_wali_linux_musl.rs
new file mode 100644
index 00000000000..a0eb4a254fc
--- /dev/null
+++ b/compiler/rustc_target/src/spec/targets/wasm32_wali_linux_musl.rs
@@ -0,0 +1,29 @@
+//! The `wasm32-wali-linux-musl` target is a wasm32 target compliant with the
+//! [WebAssembly Linux Interface](https://github.com/arjunr2/WALI).
+
+use crate::spec::{Cc, LinkerFlavor, Target, TargetMetadata, base};
+
+pub(crate) fn target() -> Target {
+    let mut options = base::linux_wasm::opts();
+
+    options
+        .add_pre_link_args(LinkerFlavor::WasmLld(Cc::No), &["--export-memory", "--shared-memory"]);
+    options.add_pre_link_args(
+        LinkerFlavor::WasmLld(Cc::Yes),
+        &["--target=wasm32-wasi-threads", "-Wl,--export-memory,", "-Wl,--shared-memory"],
+    );
+
+    Target {
+        llvm_target: "wasm32-wasi".into(),
+        metadata: TargetMetadata {
+            description: Some("WebAssembly Linux Interface with musl-libc".into()),
+            tier: Some(3),
+            host_tools: Some(false),
+            std: None,
+        },
+        pointer_width: 32,
+        data_layout: "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-i128:128-n32:64-S128-ni:1:10:20".into(),
+        arch: "wasm32".into(),
+        options,
+    }
+}
diff --git a/library/core/src/ffi/primitives.rs b/library/core/src/ffi/primitives.rs
index 6495e61b346..0a70eb4da55 100644
--- a/library/core/src/ffi/primitives.rs
+++ b/library/core/src/ffi/primitives.rs
@@ -133,7 +133,10 @@ mod c_char_definition {
 
 mod c_long_definition {
     cfg_if! {
-        if #[cfg(all(target_pointer_width = "64", not(windows)))] {
+        if #[cfg(any(
+            all(target_pointer_width = "64", not(windows)),
+            // wasm32 Linux ABI uses 64-bit long
+            all(target_arch = "wasm32", target_os = "linux")))] {
             pub(super) type c_long = i64;
             pub(super) type c_ulong = u64;
         } else {
diff --git a/library/unwind/src/libunwind.rs b/library/unwind/src/libunwind.rs
index 1a640bbde71..ced8e82b8eb 100644
--- a/library/unwind/src/libunwind.rs
+++ b/library/unwind/src/libunwind.rs
@@ -72,9 +72,12 @@ pub const unwinder_private_data_size: usize = 2;
 #[cfg(any(target_arch = "riscv64", target_arch = "riscv32"))]
 pub const unwinder_private_data_size: usize = 2;
 
-#[cfg(target_os = "emscripten")]
+#[cfg(all(target_arch = "wasm32", target_os = "emscripten"))]
 pub const unwinder_private_data_size: usize = 20;
 
+#[cfg(all(target_arch = "wasm32", target_os = "linux"))]
+pub const unwinder_private_data_size: usize = 2;
+
 #[cfg(all(target_arch = "hexagon", target_os = "linux"))]
 pub const unwinder_private_data_size: usize = 35;
 
diff --git a/src/bootstrap/configure.py b/src/bootstrap/configure.py
index c3b25646439..77151edd240 100755
--- a/src/bootstrap/configure.py
+++ b/src/bootstrap/configure.py
@@ -270,6 +270,11 @@ v(
     "loongarch64-unknown-linux-musl install directory",
 )
 v(
+    "musl-root-wali-wasm32",
+    "target.wasm32-wali-linux-musl.musl-root",
+    "wasm32-wali-linux-musl install directory",
+)
+v(
     "qemu-armhf-rootfs",
     "target.arm-unknown-linux-gnueabihf.qemu-rootfs",
     "rootfs in qemu testing, you probably don't want to use this",
diff --git a/src/bootstrap/src/core/build_steps/compile.rs b/src/bootstrap/src/core/build_steps/compile.rs
index 319a2233b1c..8cb3e3ed872 100644
--- a/src/bootstrap/src/core/build_steps/compile.rs
+++ b/src/bootstrap/src/core/build_steps/compile.rs
@@ -390,24 +390,38 @@ fn copy_self_contained_objects(
         let srcdir = builder.musl_libdir(target).unwrap_or_else(|| {
             panic!("Target {:?} does not have a \"musl-libdir\" key", target.triple)
         });
-        for &obj in &["libc.a", "crt1.o", "Scrt1.o", "rcrt1.o", "crti.o", "crtn.o"] {
-            copy_and_stamp(
-                builder,
-                &libdir_self_contained,
-                &srcdir,
-                obj,
-                &mut target_deps,
-                DependencyType::TargetSelfContained,
-            );
-        }
-        let crt_path = builder.ensure(llvm::CrtBeginEnd { target });
-        for &obj in &["crtbegin.o", "crtbeginS.o", "crtend.o", "crtendS.o"] {
-            let src = crt_path.join(obj);
-            let target = libdir_self_contained.join(obj);
-            builder.copy_link(&src, &target);
-            target_deps.push((target, DependencyType::TargetSelfContained));
+        if !target.starts_with("wasm32") {
+            for &obj in &["libc.a", "crt1.o", "Scrt1.o", "rcrt1.o", "crti.o", "crtn.o"] {
+                copy_and_stamp(
+                    builder,
+                    &libdir_self_contained,
+                    &srcdir,
+                    obj,
+                    &mut target_deps,
+                    DependencyType::TargetSelfContained,
+                );
+            }
+            let crt_path = builder.ensure(llvm::CrtBeginEnd { target });
+            for &obj in &["crtbegin.o", "crtbeginS.o", "crtend.o", "crtendS.o"] {
+                let src = crt_path.join(obj);
+                let target = libdir_self_contained.join(obj);
+                builder.copy_link(&src, &target);
+                target_deps.push((target, DependencyType::TargetSelfContained));
+            }
+        } else {
+            // For wasm32 targets, we need to copy the libc.a and crt1-command.o files from the
+            // musl-libdir, but we don't need the other files.
+            for &obj in &["libc.a", "crt1-command.o"] {
+                copy_and_stamp(
+                    builder,
+                    &libdir_self_contained,
+                    &srcdir,
+                    obj,
+                    &mut target_deps,
+                    DependencyType::TargetSelfContained,
+                );
+            }
         }
-
         if !target.starts_with("s390x") {
             let libunwind_path = copy_llvm_libunwind(builder, target, &libdir_self_contained);
             target_deps.push((libunwind_path, DependencyType::TargetSelfContained));
diff --git a/src/bootstrap/src/core/sanity.rs b/src/bootstrap/src/core/sanity.rs
index fdac7f3cb17..583b8e1198a 100644
--- a/src/bootstrap/src/core/sanity.rs
+++ b/src/bootstrap/src/core/sanity.rs
@@ -34,6 +34,7 @@ pub struct Finder {
 // Targets can be removed from this list once they are present in the stage0 compiler (usually by updating the beta compiler of the bootstrap).
 const STAGE0_MISSING_TARGETS: &[&str] = &[
     // just a dummy comment so the list doesn't get onelined
+    "wasm32-wali-linux-musl",
 ];
 
 /// Minimum version threshold for libstdc++ required when using prebuilt LLVM
diff --git a/src/doc/rustc/src/SUMMARY.md b/src/doc/rustc/src/SUMMARY.md
index b1d7e5421c1..2595a105142 100644
--- a/src/doc/rustc/src/SUMMARY.md
+++ b/src/doc/rustc/src/SUMMARY.md
@@ -97,6 +97,7 @@
     - [wasm32-wasip1](platform-support/wasm32-wasip1.md)
     - [wasm32-wasip1-threads](platform-support/wasm32-wasip1-threads.md)
     - [wasm32-wasip2](platform-support/wasm32-wasip2.md)
+    - [wasm32-wali-linux-musl](platform-support/wasm32-wali-linux.md)
     - [wasm32-unknown-emscripten](platform-support/wasm32-unknown-emscripten.md)
     - [wasm32-unknown-unknown](platform-support/wasm32-unknown-unknown.md)
     - [wasm32v1-none](platform-support/wasm32v1-none.md)
diff --git a/src/doc/rustc/src/platform-support.md b/src/doc/rustc/src/platform-support.md
index f78ab151b9c..5e5c3fe1b80 100644
--- a/src/doc/rustc/src/platform-support.md
+++ b/src/doc/rustc/src/platform-support.md
@@ -404,6 +404,7 @@ target | std | host | notes
 [`thumbv8m.main-nuttx-eabi`](platform-support/nuttx.md) | ✓ |  | ARMv8M Mainline with NuttX
 [`thumbv8m.main-nuttx-eabihf`](platform-support/nuttx.md) | ✓ |  | ARMv8M Mainline with NuttX, hardfloat
 [`wasm64-unknown-unknown`](platform-support/wasm64-unknown-unknown.md) | ? |  | WebAssembly
+[`wasm32-wali-linux-musl`](platform-support/wasm32-wali-linux.md) | ? |  | WebAssembly with [WALI](https://github.com/arjunr2/WALI)
 [`x86_64-apple-tvos`](platform-support/apple-tvos.md) | ✓ |  | x86 64-bit tvOS
 [`x86_64-apple-watchos-sim`](platform-support/apple-watchos.md) | ✓ |  | x86 64-bit Apple WatchOS simulator
 [`x86_64-pc-cygwin`](platform-support/x86_64-pc-cygwin.md) | ? |  | 64-bit x86 Cygwin |
diff --git a/src/doc/rustc/src/platform-support/wasm32-wali-linux.md b/src/doc/rustc/src/platform-support/wasm32-wali-linux.md
new file mode 100644
index 00000000000..0c46ea2c01d
--- /dev/null
+++ b/src/doc/rustc/src/platform-support/wasm32-wali-linux.md
@@ -0,0 +1,98 @@
+# `wasm32-wali-linux-*`
+
+**Tier: 3**
+
+WebAssembly targets that use the [WebAssembly Linux Interface (WALI)](https://github.com/arjunr2/WALI) with 32-bit memory. The latest status of the WALI specification and support are documented within the repo.
+
+WALI offers seamless targetability of traditional Linux applications to Wasm by exposing Linux syscalls strategically into the sandbox. Numerous applications and build system work unmodified over WALI, including complex low-level system libraries -- a list of applications are included in the research paper linked in the main repo.
+
+From the wider Wasm ecosystem perspective, implementing WALI within engines allows layering of high-level security policies (e.g. WASI) above it, arming the latter's implementations with sandboxing and portability.
+
+## Target maintainers
+
+- Arjun Ramesh [@arjunr2](https://github.com/arjunr2)
+
+## Requirements
+
+### Compilation
+This target is cross-compiled and requires an installation of the [WALI compiler/sysroot](https://github.com/arjunr2/WALI). This produces standard `wasm32` binaries with the WALI interface methods as module imports that need to be implemented by a supported engine (see the  "Execution" section below).
+
+`wali` targets *minimally require* the following LLVM feature flags:
+
+* [Bulk memory] - `+bulk-memory`
+* Mutable imported globals - `+mutable-globals`
+* [Sign-extending operations] - `+sign-ext`
+* [Threading/Atomics] - `+atomics`
+
+[Bulk memory]: https://github.com/WebAssembly/spec/blob/main/proposals/bulk-memory-operations/Overview.md
+[Sign-extending operations]: https://github.com/WebAssembly/spec/blob/main/proposals/sign-extension-ops/Overview.md
+[Threading/Atomics]: https://github.com/WebAssembly/threads/blob/main/proposals/threads/Overview.md
+
+> **Note**: Users can expect that new enabled-by-default Wasm features for LLVM are transitively incorporatable into this target -- see [wasm32-unknown-unknown](wasm32-unknown-unknown.md) for detailed information on WebAssembly features.
+
+
+> **Note**: The WALI ABI is similar to default Clang wasm32 ABIs but *not identical*. The primary difference is 64-bit `long` types as opposed to 32-bit for wasm32. This is required to mantain minimum source code changes for 64-bit host platforms currently supported. This may change in the future as the spec evolves.
+
+### Execution
+Running generated WALI binaries also requires a supported compliant engine implementation -- a working implementation in the [WebAssembly Micro-Runtime (WAMR)](https://github.com/arjunr2/WALI) is included in the repo.
+
+> **Note**: WALI is still somewhat experimental and bugs may exist in the Rust support, WALI toolchain, or the LLVM compiler. The former can be filed in Rust repos while the latter two in the WALI repo.
+
+## Building the target
+
+You can build Rust with support for the target by adding it to the `target`
+list in `config.toml`, and pointing to the toolchain artifacts from the previous section ("Requirements->Compilation"). A sample `config.toml` for the `musl` environment will look like this, where `<WALI-root>` is the absolute path to the root directory of the [WALI repo](https://github.com/arjunr2/WALI):
+
+```toml
+[build]
+target = ["wasm32-wali-linux-musl"]
+
+[target.wasm32-wali-linux-musl]
+musl-root = "<WALI>/wali-musl/sysroot"
+llvm-config = "<WALI>/llvm-project/build/bin/llvm-config"
+cc = "<WALI>/llvm-project/build/bin/clang-18"
+cxx = "<WALI>/llvm-project/build/bin/clang-18"
+ar = "<WALI>/llvm-project/build/bin/llvm-ar"
+ranlib = "<WALI>/llvm-project/build/bin/llvm-ranlib"
+llvm-libunwind = "system"
+crt-static = true
+```
+
+> The `llvm-config` settings are only temporary, and the changes will eventually be upstreamed into LLVM
+
+## Building Rust programs
+
+Rust does not yet ship pre-compiled artifacts for this target. To compile for
+this target, you will either need to build Rust with the target enabled (see
+"Building the target" above), or build your own copy of `core` by using
+`build-std` or similar.
+
+Rust program builds can use this target normally. Currently, linking WALI programs may require pointing the `linker` to the llvm build in the [Cargo config](https://doc.rust-lang.org/cargo/reference/config.html) (until LLVM is upstreamed). A `config.toml` for Cargo will look like the following:
+
+```toml
+[target.wasm32-wali-linux-musl]
+linker = "<WALI>/llvm-project/build/bin/lld"
+```
+
+Note that the following `cfg` directives are set for `wasm32-wali-linux-*`:
+
+* `cfg(target_arch = "wasm32")`
+* `cfg(target_family = {"wasm", "unix"})`
+* `cfg(target_r = "wasm")`
+* `cfg(target_os = "linux")`
+* `cfg(target_env = *)`
+
+### Restrictions
+
+Hardware or platform-specific support, besides `syscall` is mostly unsupported in WALI for ISA portability (these tend to be uncommon).
+
+## Testing
+
+Currently testing is not supported for `wali` targets and the Rust project doesn't run any tests for this target.
+
+However, standard ISA-agnostic tests for Linux should be thereotically reusable for WALI targets and minor changes. Testing integration will be continually incorporated as support evolves.
+
+
+## Cross-compilation toolchains and C code
+
+Most fully featured C code is compilable with the WALI toolchain -- examples can be seen in the repo.
diff --git a/tests/assembly/targets/targets-elf.rs b/tests/assembly/targets/targets-elf.rs
index dc564c60f80..8f2fef0e9c9 100644
--- a/tests/assembly/targets/targets-elf.rs
+++ b/tests/assembly/targets/targets-elf.rs
@@ -559,6 +559,9 @@
 //@ revisions: wasm32_wasip2
 //@ [wasm32_wasip2] compile-flags: --target wasm32-wasip2
 //@ [wasm32_wasip2] needs-llvm-components: webassembly
+//@ revisions: wasm32_wali_linux_musl
+//@ [wasm32_wali_linux_musl] compile-flags: --target wasm32-wali-linux-musl
+//@ [wasm32_wali_linux_musl] needs-llvm-components: webassembly
 //@ revisions: wasm64_unknown_unknown
 //@ [wasm64_unknown_unknown] compile-flags: --target wasm64-unknown-unknown
 //@ [wasm64_unknown_unknown] needs-llvm-components: webassembly
diff --git a/tests/run-make/musl-default-linking/rmake.rs b/tests/run-make/musl-default-linking/rmake.rs
index d203595a447..017444cfcdd 100644
--- a/tests/run-make/musl-default-linking/rmake.rs
+++ b/tests/run-make/musl-default-linking/rmake.rs
@@ -45,8 +45,21 @@ fn main() {
 
         let target_spec: serde_json::Value =
             serde_json::from_str(&target_spec_json).expect("failed to parse target-spec-json");
-        let default = &target_spec["crt-static-default"];
 
+        let target_families = &target_spec["target-family"];
+        // WebAssembly doesn't support dynamic linking yet; all musl targets
+        // need to be statically linked.
+        if target_families
+            .as_array()
+            .expect("target-family wasn't an array")
+            .iter()
+            .filter_map(|x| x.as_str())
+            .any(|family| family == "wasm")
+        {
+            continue;
+        }
+
+        let default = &target_spec["crt-static-default"];
         // If the value is `null`, then the default to dynamically link from
         // musl_base was not overridden.
         if default.is_null() {