[compiler-rt] [sanitizer_common] Don't use syscall(SYS_clone) on Linux/sparc64 (PR #100534)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Rainer Orth (rorth)

<details>
<summary>Changes</summary>

```
  SanitizerCommon-Unit :: ./Sanitizer-sparc-Test/SanitizerCommon/StartSubprocessTest
```
and every single test using the `llvm-symbolizer` `FAIL` on Linux/sparc64 in a very weird way: when using `StartSubprocess`, there's a call to `internal_fork`, but we never reach `internal_execve`.  `internal_fork` is implemented using `syscall(SYS_clone)`.  The calling convention of that syscall already varies considerably between targets, but as documented in `clone(2)`, SPARC again is widely different.  Instead of trying to match `glibc` here, this patch just calls `__fork`.

Tested on `sparc64-unknown-linux-gnu` and `x86_64-pc-linux-gnu`.

---
Full diff: https://github.com/llvm/llvm-project/pull/100534.diff


1 Files Affected:

- (modified) compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp (+6) 


``````````diff
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp
index 483a1042a6238..49f57b3404fbc 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp
@@ -826,10 +826,16 @@ uptr internal_sigaltstack(const void *ss, void *oss) {
   return internal_syscall(SYSCALL(sigaltstack), (uptr)ss, (uptr)oss);
 }
 
+extern "C" pid_t __fork(void);
+
 int internal_fork() {
 #    if SANITIZER_LINUX
 #      if SANITIZER_S390
   return internal_syscall(SYSCALL(clone), 0, SIGCHLD);
+#      elif SANITIZER_SPARC
+  // The clone syscall interface on SPARC differs massively from the rest,
+  // so fall back to __fork.
+  return __fork();
 #      else
   return internal_syscall(SYSCALL(clone), SIGCHLD, 0);
 #      endif

``````````

</details>


https://github.com/llvm/llvm-project/pull/100534