[ASAN] Pass previous stack information through __sanitizer_finish_switch_fiber

This patch extends __sanitizer_finish_switch_fiber method to optionally return previous stack base and size.

This solves the problem of coroutines/fibers library not knowing the original stack context from which the library is used. It's incorrect to assume that such context is always the default stack of current thread (e.g. one such library may be used from a fiber/coroutine created by another library). Bulding a separate stack tracking mechanism would not only duplicate AsanThread, but also require each coroutines/fibers library to integrate with it.

Author: Andrii Grynenko (andriigrynenko)
Reviewed in: https://reviews.llvm.org/D24628



git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@282582 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 13 insertions, 3 deletions

diff --git a/lib/asan/asan_thread.cc b/lib/asan/asan_thread.cc
index 14684086b..537b53d9e 100644
--- a/lib/asan/asan_thread.cc
+++ b/lib/asan/asan_thread.cc
@@ -141,7 +141,9 @@ void AsanThread::StartSwitchFiber(FakeStack **fake_stack_save, uptr bottom,
     current_fake_stack->Destroy(this->tid());
 }
 
-void AsanThread::FinishSwitchFiber(FakeStack *fake_stack_save) {
+void AsanThread::FinishSwitchFiber(FakeStack *fake_stack_save,
+                                   uptr *bottom_old,
+                                   uptr *size_old) {
   if (!atomic_load(&stack_switching_, memory_order_relaxed)) {
     Report("ERROR: finishing a fiber switch that has not started\n");
     Die();
@@ -152,6 +154,10 @@ void AsanThread::FinishSwitchFiber(FakeStack *fake_stack_save) {
     fake_stack_ = fake_stack_save;
   }
 
+  if (bottom_old)
+    *bottom_old = stack_bottom_;
+  if (size_old)
+    *size_old = stack_top_ - stack_bottom_;
   stack_bottom_ = next_stack_bottom_;
   stack_top_ = next_stack_top_;
   atomic_store(&stack_switching_, 0, memory_order_release);
@@ -447,12 +453,16 @@ void __sanitizer_start_switch_fiber(void **fakestacksave, const void *bottom,
 }
 
 SANITIZER_INTERFACE_ATTRIBUTE
-void __sanitizer_finish_switch_fiber(void* fakestack) {
+void __sanitizer_finish_switch_fiber(void* fakestack,
+                                     const void **bottom_old,
+                                     uptr *size_old) {
   AsanThread *t = GetCurrentThread();
   if (!t) {
     VReport(1, "__asan_finish_switch_fiber called from unknown thread\n");
     return;
   }
-  t->FinishSwitchFiber((FakeStack*)fakestack);
+  t->FinishSwitchFiber((FakeStack*)fakestack,
+                       (uptr*)bottom_old,
+                       (uptr*)size_old);
 }
 }