Correct atexit(3) support in MSan/NetBSD

Summary:
The NetBSD specific implementation of cxa_atexit() does not
preserve the 2nd argument if dso is equal to NULL.

Changes:

 - Split paths of handling intercepted __cxa_atexit() and atexit(3).
   This affects all supported Operating Systems.
 - Add a local stack-like structure to hold the __cxa_atexit() context.
   atexit(3) is documented in the C standard as calling callback from the
   earliest to the oldest entry. This path also fixes potential ABI
   problem of passing an argument to a function from the atexit(3)
   callback mechanism.
 - Allow usage of global vars with ctors in interceptors.
   This allows to use Vector without automatic cleaning up the structures.

This code has been modeled after TSan implementation for the same functions.

Sponsored by <The NetBSD Foundation>

Reviewers: joerg, dvyukov, eugenis, vitalybuka, kcc

Reviewed By: vitalybuka

Subscribers: llvm-commits, #sanitizers

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D40714

llvm-svn: 319967

diff --git a/compiler-rt/lib/msan/msan_interceptors.cc b/compiler-rt/lib/msan/msan_interceptors.cc
index ae9c89494442dc178b4720a9d5e4a02e1ac78325..69c1aeb732752a6a3896b3a864b75f6f7fac82c2 100644 (file)
--- a/compiler-rt/lib/msan/msan_interceptors.cc
+++ b/compiler-rt/lib/msan/msan_interceptors.cc
@@ -33,6 +33,7 @@
 #include "sanitizer_common/sanitizer_libc.h"
 #include "sanitizer_common/sanitizer_linux.h"
 #include "sanitizer_common/sanitizer_tls_get_addr.h"
+#include "sanitizer_common/sanitizer_vector.h"
 
 #if SANITIZER_NETBSD
 #define gettimeofday __gettimeofday50
@@ -1121,23 +1122,78 @@ struct MSanAtExitRecord {
   void *arg;
 };
 
-void MSanAtExitWrapper(void *arg) {
+struct InterceptorContext {
+  BlockingMutex atexit_mu;
+  Vector<struct MSanAtExitRecord *> AtExitStack;
+
+  InterceptorContext()
+      : AtExitStack() {
+  }
+};
+
+static ALIGNED(64) char interceptor_placeholder[sizeof(InterceptorContext)];
+InterceptorContext *interceptor_ctx() {
+  return reinterpret_cast<InterceptorContext*>(&interceptor_placeholder[0]);
+}
+
+void MSanAtExitWrapper() {
+  MSanAtExitRecord *r;
+  {
+    BlockingMutexLock l(&interceptor_ctx()->atexit_mu);
+
+    uptr element = interceptor_ctx()->AtExitStack.Size() - 1;
+    r = interceptor_ctx()->AtExitStack[element];
+    interceptor_ctx()->AtExitStack.PopBack();
+  }
+
+  UnpoisonParam(1);
+  ((void(*)())r->func)();
+  InternalFree(r);
+}
+
+void MSanCxaAtExitWrapper(void *arg) {
   UnpoisonParam(1);
   MSanAtExitRecord *r = (MSanAtExitRecord *)arg;
   r->func(r->arg);
   InternalFree(r);
 }
 
+static int setup_at_exit_wrapper(void(*f)(), void *arg, void *dso);
+
+// Unpoison argument shadow for C++ module destructors.
+INTERCEPTOR(int, atexit, void (*func)()) {
+  if (msan_init_is_running) return REAL(atexit)(func);
+  return setup_at_exit_wrapper((void(*)())func, 0, 0);
+}
+
 // Unpoison argument shadow for C++ module destructors.
 INTERCEPTOR(int, __cxa_atexit, void (*func)(void *), void *arg,
             void *dso_handle) {
   if (msan_init_is_running) return REAL(__cxa_atexit)(func, arg, dso_handle);
+  return setup_at_exit_wrapper((void(*)())func, arg, dso_handle);
+}
+
+static int setup_at_exit_wrapper(void(*f)(), void *arg, void *dso) {
   ENSURE_MSAN_INITED();
   MSanAtExitRecord *r =
       (MSanAtExitRecord *)InternalAlloc(sizeof(MSanAtExitRecord));
-  r->func = func;
+  r->func = (void(*)(void *a))f;
   r->arg = arg;
-  return REAL(__cxa_atexit)(MSanAtExitWrapper, r, dso_handle);
+  int res;
+  if (!dso) {
+    // NetBSD does not preserve the 2nd argument if dso is equal to 0
+    // Store ctx in a local stack-like structure
+
+    BlockingMutexLock l(&interceptor_ctx()->atexit_mu);
+
+    res = REAL(__cxa_atexit)((void (*)(void *a))MSanAtExitWrapper, 0, 0);
+    if (!res) {
+      interceptor_ctx()->AtExitStack.PushBack(r);
+    }
+  } else {
+    res = REAL(__cxa_atexit)(MSanCxaAtExitWrapper, r, dso);
+  }
+  return res;
 }
 
 static void BeforeFork() {
@@ -1535,6 +1591,9 @@ namespace __msan {
 void InitializeInterceptors() {
   static int inited = 0;
   CHECK_EQ(inited, 0);
+
+  new(interceptor_ctx()) InterceptorContext();
+
   InitializeCommonInterceptors();
   InitializeSignalInterceptors();
 
@@ -1650,6 +1709,7 @@ void InitializeInterceptors() {
 
   INTERCEPT_FUNCTION(pthread_join);
   INTERCEPT_FUNCTION(tzset);
+  INTERCEPT_FUNCTION(atexit);
   INTERCEPT_FUNCTION(__cxa_atexit);
   INTERCEPT_FUNCTION(shmat);
   INTERCEPT_FUNCTION(fork);