[PATCH] D40657: [sanitizer] Introduce a vDSO aware time function, and use it in the allocator

[Roland McGrath via Phabricator via llvm-commits]

mcgrathr added a comment.

Fuchsia bit LGTM.  Linux bit highly suspect.



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Comment at: lib/sanitizer_common/sanitizer_linux.cc:468
+extern "C" SANITIZER_WEAK_ATTRIBUTE
+int __vdso_clock_gettime(clockid_t clock, struct timespec* ts);
+bool CanUseVDSO() {
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Don't rely on these libc internals.  Just look up the real `__vdso_clock_gettime` symbol in the vDSO itself.  On some machines glibc defines a `__vdso_clock_gettime` symbol also, which is a mangled pointer, not a function as declared here.  But that's purely a libc implementation detail (it's a `GLIBC_PRIVATE` symbol) and you shouldn't pay attention to that at all.  On x86, there is no such symbol in libc and so `__vdso_clock_gettime` will reach the actual vDSO function.  But since the name is sometimes overloaded, what you probably want to do is find the vDSO with `dlopen` or suchlike and then use `dlsym` to look up `__vdso_clock_gettime` directly in the vDSO.


https://reviews.llvm.org/D40657