[compiler-rt][sanitizer] fix msghdr for musl

[deaklajos]

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.

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[llvmbot]

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

Author: Deák Lajos (deaklajos)

Changes

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 --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.

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[vitalybuka]

can you use SANITIZER_WORDSIZE == 64 instead of __LONG_MAX ?

[vitalybuka]

I don't think big endian is realy supported.
Let's assume little endian.

[vitalybuka]

do you have a link to declaration?