Index: lib/hwasan/hwasan_checks.h
===================================================================
--- lib/hwasan/hwasan_checks.h
+++ lib/hwasan/hwasan_checks.h
@@ -15,6 +15,7 @@
 #define HWASAN_CHECKS_H
 
 #include "hwasan_mapping.h"
+#include "sanitizer_common/sanitizer_common.h"
 
 namespace __hwasan {
 template <unsigned X>
@@ -23,8 +24,7 @@
   (void)p;
   // 0x900 is added to do not interfere with the kernel use of lower values of
   // brk immediate.
-  // FIXME: Add a constraint to put the pointer into x0, the same as x86 branch.
-  asm("brk %0\n\t" ::"n"(0x900 + X));
+  asm("ldr X0, %0\nbrk %1\n\t" ::"g"(p), "n"(0x900 + X));
 #elif defined(__x86_64__)
   // INT3 + NOP DWORD ptr [EAX + X] to pass X to our signal handler, 5 bytes
   // total. The pointer is passed via rdi.
@@ -42,6 +42,26 @@
   // __builtin_unreachable();
 }
 
+// Version with access size which is not power of 2
+template <unsigned X>
+__attribute__((always_inline)) static void SigTrap(uptr p, uptr size) {
+#if defined(__aarch64__)
+  asm("ldr X0, %0\n"
+      "ldr X1, %1\n"
+      "brk %2\n\t" ::"g"(p),
+      "g"(size), "n"(0x900 + X));
+#elif defined(__x86_64__)
+  // Size is stored in rsi.
+  asm volatile(
+      "int3\n"
+      "nopl %c0(%%rax)\n" ::"n"(0x40 + X),
+      "D"(p), "S"(size));
+#else
+  __builtin_trap();
+#endif
+  // __builtin_unreachable();
+}
+
 enum class ErrorAction { Abort, Recover };
 enum class AccessType { Load, Store };
 
@@ -70,9 +90,9 @@
   for (tag_t *t = shadow_first; t <= shadow_last; ++t)
     if (UNLIKELY(ptr_tag != *t)) {
       SigTrap<0x20 * (EA == ErrorAction::Recover) +
-              0x10 * (AT == AccessType::Store) + 0xf>(p);
-      if (EA == ErrorAction::Abort)
-        __builtin_unreachable();
+              0x10 * (AT == AccessType::Store) + 0xf>(p, sz);
+    if (EA == ErrorAction::Abort)
+      __builtin_unreachable();
     }
 }
 }  // end namespace __hwasan
Index: lib/hwasan/hwasan_report.cc
===================================================================
--- lib/hwasan/hwasan_report.cc
+++ lib/hwasan/hwasan_report.cc
@@ -402,11 +402,24 @@
 
   tag_t ptr_tag = GetTagFromPointer(tagged_addr);
   tag_t *tag_ptr = reinterpret_cast<tag_t*>(MemToShadow(untagged_addr));
+
+  // For accesses spanned over granule boundary tag_ptr may not point to
+  // correct tag
+  uptr granule = untagged_addr;
+  for (; *tag_ptr == ptr_tag;
+       ++tag_ptr, granule = RoundUpTo(granule + 1, 1 << kShadowScale)) {
+  }
+  CHECK(granule - untagged_addr < access_size);
   tag_t mem_tag = *tag_ptr;
+
   Printf("%s", d.Access());
   Printf("%s of size %zu at %p tags: %02x/%02x (ptr/mem) in thread T%zd\n",
          is_store ? "WRITE" : "READ", access_size, untagged_addr, ptr_tag,
          mem_tag, t->unique_id());
+  Printf("Offset to first bad byte is in range [%zu, %zu)\n",
+         granule - untagged_addr,
+         Min(access_size,
+             RoundUpTo(granule + 1, 1 << kShadowScale) - untagged_addr));
   Printf("%s", d.Default());
 
   stack->Print();
Index: test/hwasan/TestCases/mem-intrinsics.c
===================================================================
--- test/hwasan/TestCases/mem-intrinsics.c
+++ test/hwasan/TestCases/mem-intrinsics.c
@@ -21,15 +21,17 @@
 #endif
   write(STDOUT_FILENO, "recovered\n", 10);
   // WRITE: ERROR: HWAddressSanitizer: tag-mismatch on address
-  // WRITE: WRITE {{.*}} tags: [[PTR_TAG:..]]/[[MEM_TAG:..]] (ptr/mem)
+  // WRITE: WRITE of size 32 at {{.*}} tags: [[PTR_TAG:..]]/[[MEM_TAG:..]] (ptr/mem)
+  // WRITE: Offset to first bad byte is in range [16, 32)
   // WRITE: Memory tags around the buggy address (one tag corresponds to 16 bytes):
-  // WRITE: =>{{.*}}[[MEM_TAG]]
+  // WRITE: =>{{.*}}[[PTR_TAG]]{{[[:space:]]\[}}[[MEM_TAG]]
   // WRITE-NOT: recovered
 
   // READ: ERROR: HWAddressSanitizer: tag-mismatch on address
-  // READ: READ {{.*}} tags: [[PTR_TAG:..]]/[[MEM_TAG:..]] (ptr/mem)
+  // READ: READ of size 16 at {{.*}} tags: [[PTR_TAG:..]]/[[MEM_TAG:..]] (ptr/mem)
+  // READ: Offset to first bad byte is in range [0, 16)
   // READ: Memory tags around the buggy address (one tag corresponds to 16 bytes):
-  // READ: =>{{.*}}[[MEM_TAG]]
+  // READ: =>{{.*}}[[PTR_TAG]]{{[[:space:]]\[}}[[MEM_TAG]]
   // READ-NOT: recovered
 
   // RECOVER: recovered
Index: test/hwasan/TestCases/rich-stack.c
===================================================================
--- test/hwasan/TestCases/rich-stack.c
+++ test/hwasan/TestCases/rich-stack.c
@@ -60,6 +60,7 @@
 
 // R321: HWAddressSanitizer: tag-mismatch
 // R321-NEXT: WRITE of size 8
+// R321-NEXT: Offset to first bad byte is in range [0, 8)
 // R321-NEXT: in BAR
 // R321-NEXT: in FOO
 // R321-NEXT: in main