From 59dc7956ff8b8d4f06439ab24eed562db695df8a Mon Sep 17 00:00:00 2001
From: Florian Mayer <fmayer@google.com>
Date: Fri, 21 Jun 2024 16:15:12 -0700
Subject: [PATCH] [MTE] fix longjmp handling

untag_memory didn't correctly handle the case where from = to, and would
always untag the first byte.

not changing the assembly for now to make this more obvious for
cherry-picking purposes.

Test: atest bionic-unit-tests-static
Bug: 348142687
(cherry picked from https://android-review.googlesource.com/q/commit:6b174efa140304f857547e3058baff445dd2f17f)
Merged-In: I47c635897e0b50bbe4367a869d9b53fa45be0dc0
Change-Id: I47c635897e0b50bbe4367a869d9b53fa45be0dc0
---
 libc/bionic/heap_tagging.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/libc/bionic/heap_tagging.cpp b/libc/bionic/heap_tagging.cpp
index cadab3ceb..3d92404da 100644
--- a/libc/bionic/heap_tagging.cpp
+++ b/libc/bionic/heap_tagging.cpp
@@ -184,6 +184,9 @@ bool SetHeapTaggingLevel(HeapTaggingLevel tag_level) {
 
 #ifdef __aarch64__
 static inline __attribute__((no_sanitize("memtag"))) void untag_memory(void* from, void* to) {
+  if (from == to) {
+    return;
+  }
   __asm__ __volatile__(
       ".arch_extension mte\n"
       "1:\n"