[ASan] Allow to atomically modify malloc_context_size at runtime.

Summary:
Introduce __asan::malloc_context_size atomic that is used to determine
required malloc/free stack trace size. It is initialized with
common_flags()->malloc_context_size flag, but can later be overwritten
at runtime (e.g. when ASan is activated / deactivated).

Test Plan: regression test suite

Reviewers: kcc, eugenis

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D6645

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@224305 91177308-0d34-0410-b5e6-96231b3b80d8

lib/asan/asan_activation.cc

@@ -16,6 +16,7 @@
 #include "asan_allocator.h"
 #include "asan_flags.h"
 #include "asan_internal.h"
+#include "asan_stack.h"
 #include "sanitizer_common/sanitizer_flags.h"
 
 namespace __asan {
@@ -62,13 +63,12 @@ void AsanActivate() {
   // FIXME: this is not atomic, and there may be other threads alive.
   flags()->max_redzone = asan_deactivated_flags.max_redzone;
   flags()->poison_heap = asan_deactivated_flags.poison_heap;
-  common_flags()->malloc_context_size =
-      asan_deactivated_flags.malloc_context_size;
   flags()->alloc_dealloc_mismatch =
       asan_deactivated_flags.alloc_dealloc_mismatch;
 
   ParseExtraActivationFlags();
 
+  SetMallocContextSize(asan_deactivated_flags.malloc_context_size);
   ReInitializeAllocator(asan_deactivated_flags.allocator_may_return_null,
                         asan_deactivated_flags.quarantine_size);
 
@@ -77,7 +77,7 @@ void AsanActivate() {
              "malloc_context_size %d, alloc_dealloc_mismatch %d, "
              "allocator_may_return_null %d\n",
           asan_deactivated_flags.quarantine_size, flags()->max_redzone,
-          flags()->poison_heap, common_flags()->malloc_context_size,
+          flags()->poison_heap, asan_deactivated_flags.malloc_context_size,
           flags()->alloc_dealloc_mismatch,
           asan_deactivated_flags.allocator_may_return_null);
 }

lib/asan/asan_rtl.cc

@@ -71,8 +71,6 @@ static void AsanCheckFailed(const char *file, int line, const char *cond,
 }
 
 // -------------------------- Flags ------------------------- {{{1
-static const int kDefaultMallocContextSize = 30;
-
 Flags asan_flags_dont_use_directly;  // use via flags().
 
 static const char *MaybeCallAsanDefaultOptions() {
@@ -93,7 +91,6 @@ static const char *MaybeUseAsanDefaultOptionsCompileDefinition() {
 static void ParseFlagsFromString(Flags *f, const char *str) {
   CommonFlags *cf = common_flags();
   ParseCommonFlagsFromString(cf, str);
-  CHECK((uptr)cf->malloc_context_size <= kStackTraceMax);
   // Please write meaningful flag descriptions when adding new flags.
   ParseFlag(str, &f->quarantine_size, "quarantine_size",
             "Size (in bytes) of quarantine used to detect use-after-free "
@@ -322,7 +319,8 @@ void InitializeFlags(Flags *f, const char *env) {
   if (f->strict_init_order) {
     f->check_initialization_order = true;
   }
-  CHECK_LE(flags()->min_uar_stack_size_log, flags()->max_uar_stack_size_log);
+  CHECK_LE((uptr)cf->malloc_context_size, kStackTraceMax);
+  CHECK_LE(f->min_uar_stack_size_log, f->max_uar_stack_size_log);
 }
 
 // Parse flags that may change between startup and activation.
@@ -572,6 +570,8 @@ static void AsanInitInternal() {
   const char *options = GetEnv("ASAN_OPTIONS");
   InitializeFlags(flags(), options);
 
+  SetMallocContextSize(common_flags()->malloc_context_size);
+
   InitializeHighMemEnd();
 
   // Make sure we are not statically linked.

lib/asan/asan_stack.cc

@@ -13,6 +13,21 @@
 //===----------------------------------------------------------------------===//
 #include "asan_internal.h"
 #include "asan_stack.h"
+#include "sanitizer_common/sanitizer_atomic.h"
+
+namespace __asan {
+
+static atomic_uint32_t malloc_context_size;
+
+void SetMallocContextSize(u32 size) {
+  atomic_store(&malloc_context_size, size, memory_order_release);
+}
+
+u32 GetMallocContextSize() {
+  return atomic_load(&malloc_context_size, memory_order_acquire);
+}
+
+}  // namespace __asan
 
 // ------------------ Interface -------------- {{{1
 

lib/asan/asan_stack.h

@@ -21,6 +21,11 @@
 
 namespace __asan {
 
+static const u32 kDefaultMallocContextSize = 30;
+
+void SetMallocContextSize(u32 size);
+u32 GetMallocContextSize();
+
 // Get the stack trace with the given pc and bp.
 // The pc will be in the position 0 of the resulting stack trace.
 // The bp may refer to the current frame or to the caller's frame.
@@ -93,9 +98,8 @@ void GetStackTraceWithPcBpAndContext(BufferedStackTrace *stack, uptr max_depth,
 #define GET_STACK_TRACE_THREAD                                    \
   GET_STACK_TRACE(kStackTraceMax, true)
 
-#define GET_STACK_TRACE_MALLOC                                    \
-  GET_STACK_TRACE(common_flags()->malloc_context_size,            \
-                  common_flags()->fast_unwind_on_malloc)
+#define GET_STACK_TRACE_MALLOC                                                 \
+  GET_STACK_TRACE(GetMallocContextSize(), common_flags()->fast_unwind_on_malloc)
 
 #define GET_STACK_TRACE_FREE GET_STACK_TRACE_MALLOC
 

lib/sanitizer_common/sanitizer_stacktrace.cc

@@ -120,7 +120,7 @@ void BufferedStackTrace::PopStackFrames(uptr count) {
 uptr BufferedStackTrace::LocatePcInTrace(uptr pc) {
   // Use threshold to find PC in stack trace, as PC we want to unwind from may
   // slightly differ from return address in the actual unwinded stack trace.
-  const int kPcThreshold = 288;
+  const int kPcThreshold = 304;
   for (uptr i = 0; i < size; ++i) {
     if (MatchPc(pc, trace[i], kPcThreshold))
       return i;