[PATCH] D40504: [scudo] Workaround for uninitialized Bionic globals

[Kostya Kortchinsky via Phabricator via llvm-commits]

cryptoad created this revision.
Herald added a subscriber: srhines.

Bionic doesn't initialize its globals early enough. This causes issues when
trying to access them from a preinit_array (b/25751302) or from another
constructor called before the libc one (b/68046352). __progname is initialized
after the other globals, so we can check its value to know if calling
`getauxval` is safe.


https://reviews.llvm.org/D40504

Files:
  lib/scudo/scudo_utils.cpp


Index: lib/scudo/scudo_utils.cpp
===================================================================
--- lib/scudo/scudo_utils.cpp
+++ lib/scudo/scudo_utils.cpp
@@ -96,8 +96,18 @@
 bool hasHardwareCRC32ARMPosix() { return false; }
 # endif  // SANITIZER_POSIX
 
+// Bionic doesn't initialize its globals early enough. This causes issues when
+// trying to access them from a preinit_array (b/25751302) or from another
+// constructor called before the libc one (b/68046352). __progname is
+// initialized after the other globals, so we can check its value to know if
+// calling getauxval is safe.
+extern "C" SANITIZER_WEAK_ATTRIBUTE char *__progname;
+INLINE bool areBionicGlobalsInitialized() {
+  return !SANITIZER_ANDROID || (&__progname && __progname);
+}
+
 bool hasHardwareCRC32() {
-  if (&getauxval)
+  if (&getauxval && areBionicGlobalsInitialized())
     return !!(getauxval(AT_HWCAP) & HWCAP_CRC32);
   return hasHardwareCRC32ARMPosix();
 }


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