[ASan] Change fake stack and local variables handling.

This commit changes the way we get fake stack from ASan runtime
(to find use-after-return errors) and the way we represent local
variables:
  - __asan_stack_malloc function now returns pointer to newly allocated
    fake stack frame, or NULL if frame cannot be allocated. It doesn't
    take pointer to real stack as an input argument, it is calculated
    inside the runtime.
  - __asan_stack_free function doesn't take pointer to real stack as
    an input argument. Now this function is never called if fake stack
    frame wasn't allocated.
  - __asan_init version is bumped to reflect changes in the ABI.
  - new flag "-asan-stack-dynamic-alloca" allows to store all the
    function local variables in a dynamic alloca, instead of the static
    one. It reduces the stack space usage in use-after-return mode
    (dynamic alloca will not be called if the local variables are stored
    in a fake stack), and improves the debug info quality for local
    variables (they will not be described relatively to %rbp/%rsp, which
    are assumed to be clobbered by function calls). This flag is turned
    off by default for now, but I plan to turn it on after more
    testing.

llvm-svn: 224063

2 files changed, 14 insertions, 13 deletions

diff --git a/compiler-rt/lib/asan/asan_fake_stack.cc b/compiler-rt/lib/asan/asan_fake_stack.cc
index c95bc11f6cd..86d285e36f3 100644
--- a/compiler-rt/lib/asan/asan_fake_stack.cc
+++ b/compiler-rt/lib/asan/asan_fake_stack.cc
@@ -192,20 +192,19 @@ static FakeStack *GetFakeStackFast() {
   return GetFakeStack();
 }
 
-ALWAYS_INLINE uptr OnMalloc(uptr class_id, uptr size, uptr real_stack) {
+ALWAYS_INLINE uptr OnMalloc(uptr class_id, uptr size) {
   FakeStack *fs = GetFakeStackFast();
-  if (!fs) return real_stack;
+  if (!fs) return 0;
+  uptr local_stack;
+  uptr real_stack = reinterpret_cast<uptr>(&local_stack);
   FakeFrame *ff = fs->Allocate(fs->stack_size_log(), class_id, real_stack);
-  if (!ff)
-    return real_stack;  // Out of fake stack, return the real one.
+  if (!ff) return 0;  // Out of fake stack.
   uptr ptr = reinterpret_cast<uptr>(ff);
   SetShadow(ptr, size, class_id, 0);
   return ptr;
 }
 
-ALWAYS_INLINE void OnFree(uptr ptr, uptr class_id, uptr size, uptr real_stack) {
-  if (ptr == real_stack)
-    return;
+ALWAYS_INLINE void OnFree(uptr ptr, uptr class_id, uptr size) {
   FakeStack::Deallocate(ptr, class_id);
   SetShadow(ptr, size, class_id, kMagic8);
 }
@@ -216,12 +215,12 @@ ALWAYS_INLINE void OnFree(uptr ptr, uptr class_id, uptr size, uptr real_stack) {
 using namespace __asan;
 #define DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(class_id)                       \
   extern "C" SANITIZER_INTERFACE_ATTRIBUTE uptr                                \
-  __asan_stack_malloc_##class_id(uptr size, uptr real_stack) {                 \
-    return OnMalloc(class_id, size, real_stack);                               \
+      __asan_stack_malloc_##class_id(uptr size) {                              \
+    return OnMalloc(class_id, size);                                           \
   }                                                                            \
   extern "C" SANITIZER_INTERFACE_ATTRIBUTE void __asan_stack_free_##class_id(  \
-      uptr ptr, uptr size, uptr real_stack) {                                  \
-    OnFree(ptr, class_id, size, real_stack);                                   \
+      uptr ptr, uptr size) {                                                   \
+    OnFree(ptr, class_id, size);                                               \
   }
 
 DEFINE_STACK_MALLOC_FREE_WITH_CLASS_ID(0)
diff --git a/compiler-rt/lib/asan/asan_init_version.h b/compiler-rt/lib/asan/asan_init_version.h
index 77aea81bd29..6cf57c4aa2a 100644
--- a/compiler-rt/lib/asan/asan_init_version.h
+++ b/compiler-rt/lib/asan/asan_init_version.h
@@ -25,8 +25,10 @@ extern "C" {
   //         contains the function PC as the 3-rd field (see
   //         DescribeAddressIfStack).
   // v3=>v4: added '__asan_global_source_location' to __asan_global.
-  #define __asan_init __asan_init_v4
-  #define __asan_init_name "__asan_init_v4"
+  // v4=>v5: changed the semantics and format of __asan_stack_malloc_ and
+  //         __asan_stack_free_ functions.
+  #define __asan_init __asan_init_v5
+  #define __asan_init_name "__asan_init_v5"
 }
 
 #endif  // ASAN_INIT_VERSION_H