[compiler-rt] [compiler-rt][sanitizer] fix msghdr for musl (PR #136195)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

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

Author: Deák Lajos (deaklajos)

<details>
<summary>Changes</summary>

Ran into the issue on Alpine when building with TSAN that `__sanitizer_msghdr` and the `msghdr` provided by musl did not match.
This caused lots of tsan reports and an eventual termination of the application by the oom during a `sendmsg`.

---
Full diff: https://github.com/llvm/llvm-project/pull/136195.diff


1 Files Affected:

- (modified) compiler-rt/lib/sanitizer_common/sanitizer_platform_limits_posix.h (+33) 


``````````diff
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_platform_limits_posix.h b/compiler-rt/lib/sanitizer_common/sanitizer_platform_limits_posix.h
index 348bb4f27aec3..899bd22bbd309 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_platform_limits_posix.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_platform_limits_posix.h
@@ -476,6 +476,39 @@ struct __sanitizer_cmsghdr {
   int cmsg_level;
   int cmsg_type;
 };
+#elif SANITIZER_MUSL
+struct __sanitizer_msghdr {
+  void *msg_name;
+  unsigned msg_namelen;
+  struct __sanitizer_iovec *msg_iov;
+#  if __LONG_MAX > 0x7fffffff && __BYTE_ORDER == __BIG_ENDIAN
+  int __pad1;
+#  endif
+  int msg_iovlen;
+#  if __LONG_MAX > 0x7fffffff && __BYTE_ORDER == __LITTLE_ENDIAN
+  int __pad1;
+#  endif
+  void *msg_control;
+#  if __LONG_MAX > 0x7fffffff && __BYTE_ORDER == __BIG_ENDIAN
+  int __pad2;
+#  endif
+  unsigned msg_controllen;
+#  if __LONG_MAX > 0x7fffffff && __BYTE_ORDER == __LITTLE_ENDIAN
+  int __pad2;
+#  endif
+  int msg_flags;
+};
+struct __sanitizer_cmsghdr {
+#  if __LONG_MAX > 0x7fffffff && __BYTE_ORDER == __BIG_ENDIAN
+  int __pad1;
+#  endif
+  unsigned cmsg_len;
+#  if __LONG_MAX > 0x7fffffff && __BYTE_ORDER == __LITTLE_ENDIAN
+  int __pad1;
+#  endif
+  int cmsg_level;
+  int cmsg_type;
+};
 #else
 // In POSIX, int msg_iovlen; socklen_t msg_controllen; socklen_t cmsg_len; but
 // many implementations don't conform to the standard.

``````````

</details>


https://github.com/llvm/llvm-project/pull/136195