[hwasan] Add __hwasan_handle_longjmp.

[eugenis]

Summary

A callback to annotate longjmp-like code.

Unlike __asan_handle_no_return, in hwasan we can not conservatively
"unpoison" the entire thread stack, because there is no such thing as
unpoisoned memory. Pointer and memory tags must always match.

[eugenis]

ping

compiler-rt/include/sanitizer/hwasan_interface.h

#endif
   // Mark region of memory with the given tag. Both address and size need to be
   // 16-byte aligned.
   void __hwasan_tag_memory(const volatile void *p, unsigned char tag,
                            size_t size);
 
   /// 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);
 
   int __sanitizer_posix_memalign(void **memptr, size_t alignment, size_t size);
   void * __sanitizer_memalign(size_t alignment, size_t size);
   void * __sanitizer_aligned_alloc(size_t alignment, size_t size);
   void * __sanitizer___libc_memalign(size_t alignment, size_t size);

compiler-rt/lib/hwasan/hwasan.cc

 void __hwasan_tag_memory(uptr p, u8 tag, uptr sz) {
   TagMemoryAligned(p, sz, tag);
 }
 
 uptr __hwasan_tag_pointer(uptr p, u8 tag) {
   return AddTagToPointer(p, tag);
 }
 
+void __hwasan_handle_longjmp(const void *sp_dst) {
+  uptr dst = (uptr)sp_dst;
+  // HWASan does not support tagged SP.
+  CHECK(GetTagFromPointer(dst) == 0);
+
+  uptr sp = (uptr)__builtin_frame_address(0);
+  static const uptr kMaxExpectedCleanupSize = 64 << 20;  // 64M
+  if (dst < sp || dst - sp > kMaxExpectedCleanupSize) {
+    Report(
+        "WARNING: HWASan is ignoring requested __hwasan_handle_longjmp: "
+        "stack top: %p; target %p; distance: %p (%zd)\n"
+        "False positive error reports may follow\n",
+        (void *)sp, (void *)dst, dst - sp);
+    return;
+  }
+  TagMemory(sp, dst - sp, 0);
+}
+
 static const u8 kFallbackTag = 0xBB;
 
 u8 __hwasan_generate_tag() {
   HwasanThread *t = GetCurrentThread();
   if (!t) return kFallbackTag;
   return t->GenerateRandomTag();
 }
 

compiler-rt/lib/hwasan/hwasan_interface_internal.h

 
 SANITIZER_INTERFACE_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
 /* OPTIONAL */ const char* __hwasan_default_options();
 
 SANITIZER_INTERFACE_ATTRIBUTE
 void __hwasan_print_shadow(const void *x, uptr size);
 
 SANITIZER_INTERFACE_ATTRIBUTE
+void __hwasan_handle_longjmp(const void *sp_dst);
+
+SANITIZER_INTERFACE_ATTRIBUTE
 u16 __sanitizer_unaligned_load16(const uu16 *p);
 
 SANITIZER_INTERFACE_ATTRIBUTE
 u32 __sanitizer_unaligned_load32(const uu32 *p);
 
 SANITIZER_INTERFACE_ATTRIBUTE
 u64 __sanitizer_unaligned_load64(const uu64 *p);
 

compiler-rt/test/hwasan/TestCases/longjmp.cc

+// RUN: %clangxx_hwasan -O0 -DNEGATIVE %s -o %t && %run %t 2>&1
+// RUN: %clangxx_hwasan -O0 %s -o %t && not %run %t 2>&1 | FileCheck %s
+
+// REQUIRES: stable-runtime
+
+#include <stdlib.h>
+#include <assert.h>
+#include <sanitizer/hwasan_interface.h>
+
+__attribute__((noinline))
+int f(void *caller_frame) {
+  char z[32] = {};
+  char *volatile p = z;
+  // Tag of local is never zero.
+  assert(__hwasan_tag_pointer(p, 0) != p);
+#ifndef NEGATIVE
+  // This will destroy shadow of "z", and the following load will crash.
+  __hwasan_handle_longjmp(caller_frame);
+#endif
+  return p[0];
+}
+
+int main() {
+  return f(__builtin_frame_address(0));
+  // CHECK: READ of size 8
+  // CHECK: pointer tag
+  // CHECK: memory tag 0x0
+}