Revert "Revert "[hwasan] Add __hwasan_handle_longjmp.""

This reapplies commit r339935 with the following changes:
* make longjmp test C, not C++, to avoid dependency on libc++/libstdc++
* untag pointer in memset interceptor

x86_64 does not have TBI, so hwasan barely works there. Tests must be carefully
written in a way that does not leak tagged pointer to system libraries.

1 files changed, 7 insertions, 0 deletions

diff --git a/compiler-rt/include/sanitizer/hwasan_interface.h b/compiler-rt/include/sanitizer/hwasan_interface.h
index 9ca73bc1072..78644aa9d4f 100644
--- a/compiler-rt/include/sanitizer/hwasan_interface.h
+++ b/compiler-rt/include/sanitizer/hwasan_interface.h
@@ -40,6 +40,13 @@ extern "C" {
   /// Set pointer tag. Previous tag is lost.
   void *__hwasan_tag_pointer(const volatile void *p, unsigned char tag);
 
+  // Set memory tag from the current SP address to the given address to zero.
+  // This is meant to annotate longjmp and other non-local jumps.
+  // This function needs to know the (almost) exact destination frame address;
+  // clearing shadow for the entire thread stack like __asan_handle_no_return
+  // does would cause false reports.
+  void __hwasan_handle_longjmp(const void *sp_dst);
+
   // Print shadow and origin for the memory range to stderr in a human-readable
   // format.
   void __hwasan_print_shadow(const volatile void *x, size_t size);