[PATCH] D55711: Don't trigger sanitizer initialization from `sysctlbyname` interceptor.

[Dan Liew via Phabricator via llvm-commits]

delcypher created this revision.
delcypher added reviewers: kubamracek, george.karpenkov, devnexen, vitalybuka, krytarowski.
Herald added a subscriber: Sanitizers.

This fixes the `ThreadSanitizer-x86_64-iossim` testsuite which broke
when r348770 (https://reviews.llvm.org/D55473) landed.

The root cause of the problem is that early-on during the iOS simulator
init process a call to `sysctlbyname` is issued. If the TSan initializer
is triggered at this point it will eventually trigger a call to
`__cxa_at_exit(...)`. This call then aborts because the library
implementing this function is not yet had its initialization function
called.

rdar://problem/46696934


Repository:
  rCRT Compiler Runtime

https://reviews.llvm.org/D55711

Files:
  lib/sanitizer_common/sanitizer_common_interceptors.inc


Index: lib/sanitizer_common/sanitizer_common_interceptors.inc
===================================================================
--- lib/sanitizer_common/sanitizer_common_interceptors.inc
+++ lib/sanitizer_common/sanitizer_common_interceptors.inc
@@ -7561,6 +7561,15 @@
 INTERCEPTOR(int, sysctlbyname, char *sname, void *oldp, SIZE_T *oldlenp,
             void *newp, SIZE_T newlen) {
   void *ctx;
+  if (UNLIKELY(COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED)) {
+    // On Darwin iOS simulators `sysctlbyname` gets called early
+    // during init. If we do TSan init now we'll trigger a
+    // call to `__cxa_atexit` which will crash due the implementing
+    // library not being properly initialized. To avoid this simply
+    // don't intercept this function until init has been triggered
+    // from elsewhere.
+    return REAL(sysctlbyname)(sname, oldp, oldlenp, newp, newlen);
+  }
   COMMON_INTERCEPTOR_ENTER(ctx, sysctlbyname, sname, oldp, oldlenp, newp,
                            newlen);
   if (sname)


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