[sanitizer] Avoid calling a nullptr in MonotonicNanoTime if interceptors are not yet initialized

There's a TSan startup crash on Linux when used in Swift programs, where MonotonicNanoTime will try to call real_clock_gettime and then jump to NULL because interceptors are not yet initialized. This is on Ubuntu 18.04. Looks like TSan's main Initialize() function is called at a point where __progname is already set, but interceptors aren't yet set up. Let's fix this by checking whether interceptors are initialized in MonotonicNanoTime.

Differential Revision: https://reviews.llvm.org/D53528



git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@345174 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 2 deletions

diff --git a/lib/sanitizer_common/sanitizer_linux_libcdep.cc b/lib/sanitizer_common/sanitizer_linux_libcdep.cc
index 7859557c8..93b68ed4b 100644
--- a/lib/sanitizer_common/sanitizer_linux_libcdep.cc
+++ b/lib/sanitizer_common/sanitizer_linux_libcdep.cc
@@ -782,12 +782,15 @@ INLINE bool CanUseVDSO() {
 
 // MonotonicNanoTime is a timing function that can leverage the vDSO by calling
 // clock_gettime. real_clock_gettime only exists if clock_gettime is
-// intercepted, so define it weakly and use it if available.
+// intercepted, so define it weakly and use it if available. MonotonicNanoTime
+// might also be called when interceptors are not yet initialized, so check for
+// that as well.
 extern "C" SANITIZER_WEAK_ATTRIBUTE
 int real_clock_gettime(u32 clk_id, void *tp);
+namespace __interception { int (*real_clock_gettime)(u32 clk_id, void *tp); }
 u64 MonotonicNanoTime() {
   timespec ts;
-  if (CanUseVDSO()) {
+  if (CanUseVDSO() && __interception::real_clock_gettime) {
     if (&real_clock_gettime)
       real_clock_gettime(CLOCK_MONOTONIC, &ts);
     else