[compiler-rt] [tsan] Lazily call 'personality' to minimize sandbox violations (PR #79334)

[Thurston Dang via llvm-commits]

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@@ -267,6 +267,14 @@ static void ReExecIfNeeded() {
   if (reexec) {
     // Don't check the address space since we're going to re-exec anyway.
   } else if (!CheckAndProtect(false, false, false)) {
+    // ASLR personality check.
+    // N.B. 'personality' is sometimes forbidden by sandboxes, so we only call
+    // this as a last resort (when the memory mapping is incompatible and TSan
+    // would fail anyway).
+    int old_personality = personality(0xffffffff);
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thurstond wrote:

It will be flaky on bots that have very high-entropy ASLR. AFAIK there are currently no such bots (because without the re-exec patch, all TSan tests would be failing consistently on those bots).

With that caveat in mind, please let me know if you would prefer to not test 'personality'.

https://github.com/llvm/llvm-project/pull/79334