commit 45b29f13bbefd1edc1d16a15bb4c1f8e8d8068fc
author Florian Mayer <fmayer@google.com> Fri Jun 21 18:01:52 2024 +0000
committer Florian Mayer <fmayer@google.com> Fri Jun 21 18:14:12 2024 +0000
tree 0adcf18081521c8ec35f2d47a39993deccf1ba08
parent b8e7b3e77b3478ef06c8a30ad66c20ff7532df47

Revert "[MTE] allocate ring buffer for stack history"

This reverts commit 10d11ddfcb52122db52ac9f15b4884f663e9915d.

Reason for revert: b/348239278

Change-Id: I14a1a3177ecbf5d8cf44836dc790c501c102960a

libc/bionic/libc_init_static.cpp

diff --git a/libc/bionic/libc_init_static.cpp b/libc/bionic/libc_init_static.cpp
index ac97376..3da0a92 100644
--- a/libc/bionic/libc_init_static.cpp
+++ b/libc/bionic/libc_init_static.cpp
@@ -289,7 +289,11 @@
 
   // We can't short-circuit the environment override, as `stack` is still inherited from the
   // binary's settings.
-  get_environment_memtag_setting(&level);
+  if (get_environment_memtag_setting(&level)) {
+    if (level == M_HEAP_TAGGING_LEVEL_NONE || level == M_HEAP_TAGGING_LEVEL_TBI) {
+      *stack = false;
+    }
+  }
   return level;
 }
 
@@ -325,14 +329,13 @@
   bool memtag_stack = false;
   HeapTaggingLevel level =
       __get_tagging_level(memtag_dynamic_entries, phdr_start, phdr_ct, load_bias, &memtag_stack);
-  // initial_memtag_stack is used by the linker (in linker.cpp) to communicate than any library
-  // linked by this executable enables memtag-stack.
-  // memtag_stack is also set for static executables if they request memtag stack via the note,
-  // in which case it will differ from initial_memtag_stack.
-  if (__libc_shared_globals()->initial_memtag_stack || memtag_stack) {
+  // This is used by the linker (in linker.cpp) to communicate than any library linked by this
+  // executable enables memtag-stack.
+  if (__libc_shared_globals()->initial_memtag_stack) {
+    if (!memtag_stack) {
+      async_safe_format_log(ANDROID_LOG_INFO, "libc", "enabling PROT_MTE as requested by linker");
+    }
     memtag_stack = true;
-    __libc_shared_globals()->initial_memtag_stack_abi = true;
-    __get_bionic_tcb()->tls_slot(TLS_SLOT_STACK_MTE) = __allocate_stack_mte_ringbuffer(0, nullptr);
   }
   if (int64_t timed_upgrade = __get_memtag_upgrade_secs()) {
     if (level == M_HEAP_TAGGING_LEVEL_ASYNC) {