platform docs: clarify hexagon-unknown-none-elf example, add hexagon-unknown-linux-musl

src/doc/rustc/src/SUMMARY.md

@@ -39,6 +39,7 @@
     - [\*-unknown-fuchsia](platform-support/fuchsia.md)
     - [\*-kmc-solid_\*](platform-support/kmc-solid.md)
     - [csky-unknown-linux-gnuabiv2\*](platform-support/csky-unknown-linux-gnuabiv2.md)
+    - [hexagon-unknown-linux-musl](platform-support/hexagon-unknown-linux-musl.md)
     - [hexagon-unknown-none-elf](platform-support/hexagon-unknown-none-elf.md)
     - [loongarch\*-unknown-linux-\*](platform-support/loongarch-linux.md)
     - [loongarch\*-unknown-none\*](platform-support/loongarch-none.md)

src/doc/rustc/src/platform-support.md

@@ -286,8 +286,8 @@ target | std | host | notes
 `bpfel-unknown-none` | * |  | BPF (little endian)
 `csky-unknown-linux-gnuabiv2` | ✓ |  | C-SKY abiv2 Linux (little endian)
 `csky-unknown-linux-gnuabiv2hf` | ✓ |  | C-SKY abiv2 Linux, hardfloat (little endian)
-[`hexagon-unknown-none-elf`](platform-support/hexagon-unknown-none-elf.md)| * | Bare Hexagon (v60+, HVX)
-`hexagon-unknown-linux-musl` | ? |  |
+[`hexagon-unknown-none-elf`](platform-support/hexagon-unknown-none-elf.md)| * | | Bare Hexagon (v60+, HVX)
+[`hexagon-unknown-linux-musl`](platform-support/hexagon-unknown-linux-musl.md) | ✓ | | Hexagon Linux
 `i386-apple-ios` | ✓ |  | 32-bit x86 iOS [^x86_32-floats-return-ABI]
 [`i586-pc-nto-qnx700`](platform-support/nto-qnx.md) | * |  | 32-bit x86 QNX Neutrino 7.0 RTOS  [^x86_32-floats-return-ABI]
 [`i586-unknown-netbsd`](platform-support/netbsd.md) | ✓ |  | 32-bit x86, restricted to Pentium

src/doc/rustc/src/platform-support/hexagon-unknown-linux-musl.md

@@ -0,0 +1,102 @@
+# `hexagon-unknown-linux-musl`
+
+**Tier: 3**
+
+Target for cross-compiling Linux user-mode applications targeting the Hexagon
+DSP architecture.
+
+| Target                   | Descriptions                              |
+| ------------------------ | ----------------------------------------- |
+| hexagon-unknown-linux-musl | Hexagon 32-bit Linux |
+
+## Target maintainers
+
+- [Brian Cain](https://github.com/androm3da), `bcain@quicinc.com`
+
+## Requirements
+The target is cross-compiled. This target supports `std`.  By default, code
+generated with this target should run on Hexagon DSP hardware.
+
+- `-Ctarget-cpu=hexagonv73` adds support for instructions defined up to Hexagon V73.
+
+Binaries can be run using QEMU user emulation. On Debian-based systems, it should be
+sufficient to install the package `qemu-user-static` to be able to run simple static
+binaries:
+
+```text
+# apt install qemu-user-static
+# qemu-hexagon-static ./hello
+```
+
+In order to build linux programs with Rust, you will require a linker capable
+of targeting hexagon.  You can use `clang`/`lld` from the [hexagon toolchain
+using exclusively public open source repos](https://github.com/quic/toolchain_for_hexagon/releases).
+
+Also included in that toolchain is the C library that can be used when creating
+dynamically linked executables.
+
+```text
+# /opt/clang+llvm-18.1.0-cross-hexagon-unknown-linux-musl/x86_64-linux-gnu/bin/qemu-hexagon -L /opt/clang+llvm-18.1.0-cross-hexagon-unknown-linux-musl/x86_64-linux-gnu/target/hexagon-unknown-linux-musl/usr/ ./hello
+```
+
+## Building the target
+Because it is Tier 3, rust does not yet ship pre-compiled artifacts for this
+target.
+
+Therefore, you can build Rust with support for the target by adding it to the
+target list in `config.toml`, a sample configuration is shown below.
+
+```toml
+[build]
+target = [ "hexagon-unknown-linux-musl"]
+
+[target.hexagon-unknown-linux-musl]
+
+cc = "hexagon-unknown-linux-musl-clang"
+cxx = "hexagon-unknown-linux-musl-clang++"
+linker = "hexagon-unknown-linux-musl-clang"
+ar = "hexagon-unknown-linux-musl-ar"
+ranlib = "hexagon-unknown-linux-musl-ranlib"
+musl-root = "/opt/clang+llvm-18.1.0-cross-hexagon-unknown-linux-musl/x86_64-linux-gnu/target/hexagon-unknown-linux-musl/usr"
+llvm-libunwind = 'in-tree'
+qemu-rootfs = "/opt/clang+llvm-18.1.0-cross-hexagon-unknown-linux-musl/x86_64-linux-gnu/target/hexagon-unknown-linux-musl/usr"
+```
+
+
+## Testing
+
+Currently there is no support to run the rustc test suite for this target.
+
+
+## Building Rust programs
+
+Download and install the hexagon open source toolchain from https://github.com/quic/toolchain_for_hexagon/releases
+
+The following `.cargo/config` is needed inside any project directory to build
+for the Hexagon Linux target:
+
+```toml
+[build]
+target = "hexagon-unknown-linux-musl"
+
+[target.hexagon-unknown-linux-musl]
+linker = "hexagon-unknown-linux-musl-clang"
+ar = "hexagon-unknown-linux-musl-ar"
+runner = "qemu-hexagon -L /opt/clang+llvm-18.1.0-cross-hexagon-unknown-linux-musl/x86_64-linux-gnu/target/hexagon-unknown-linux-musl/usr"
+```
+
+Edit the "runner" in `.cargo/config` to point to the path to your toolchain's
+C library.
+
+```text
+...
+runner = "qemu-hexagon -L /path/to/my/inst/clang+llvm-18.1.0-cross-hexagon-unknown-linux-musl/x86_64-linux-gnu/target/hexagon-unknown-linux-musl/usr"
+...
+```
+
+Build/run your rust program with `qemu-hexagon` in your `PATH`:
+
+```text
+export PATH=/path/to/my/inst/clang+llvm-18.1.0-cross-hexagon-unknown-linux-musl/x86_64-linux-gnu/bin/:$PATH
+cargo run -Zbuild-std -Zbuild-std-features=llvm-libunwind
+```

src/doc/rustc/src/platform-support/hexagon-unknown-none-elf.md

@@ -41,6 +41,8 @@ target = ["<target for your host>", "hexagon-unknown-none-elf"]
 cc = "hexagon-unknown-none-elf-clang"
 cxx = "hexagon-unknown-none-elf-clang++"
 linker = "hexagon-unknown-none-elf-clang"
+ranlib = "hexagon-unknown-none-elf-ranlib"
+ar = "hexagon-unknown-none-elf-ar"
 llvm-libunwind = 'in-tree'
 ```
 
@@ -142,7 +144,7 @@ ${cc} --target=hexagon-unknown-none-elf -o testit \
     ${g0_lib_path}/init.o \
     -L${sdk_libs}/${q6_arch}/ \
     -L${sdk_libs}/ \
-    testit.c \
+    wrap.c \
     target/hexagon-unknown-none-elf/${build_cfg}/libdemo1_hexagon.rlib \
     target/hexagon-unknown-none-elf/${build_cfg}/deps/libcore-*.rlib \
     target/hexagon-unknown-none-elf/${build_cfg}/deps/libcompiler_builtins-*.rlib \
@@ -217,7 +219,18 @@ fn rust_eh_personality() {}
 
 ```
 
-Next, save the script below as `build.sh` and edit it to suit your
+Next, create a C program as an entry point, save the content below as
+`wrap.c`:
+
+```C
+int hello();
+
+int main() {
+    hello();
+}
+```
+
+Then, save the script below as `build.sh` and edit it to suit your
 environment.  The script below will build a shared object against the QuRT
 RTOS which is suitable for emulation or on-device testing when loaded via
 the fastrpc-shell.
@@ -248,7 +261,7 @@ ${cc} --target=hexagon-unknown-none-elf -o testit.so \
       -Wl,--wrap=realloc \
       -Wl,--wrap=memalign \
     -m${q6_arch} \
-    testit.c \
+    wrap.c \
     target/hexagon-unknown-none-elf/${build_cfg}/libdemo2_hexagon.rlib \
     target/hexagon-unknown-none-elf/${build_cfg}/deps/libcore-*.rlib \
     target/hexagon-unknown-none-elf/${build_cfg}/deps/libcompiler_builtins-*.rlib \