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

This reverts commit 10d11ddfcb52122db52ac9f15b4884f663e9915d.

Reason for revert: b/348239278

Change-Id: I14a1a3177ecbf5d8cf44836dc790c501c102960a
diff --git a/libc/private/bionic_globals.h b/libc/private/bionic_globals.h
index a1bebda..0949056 100644
--- a/libc/private/bionic_globals.h
+++ b/libc/private/bionic_globals.h
@@ -76,23 +76,10 @@
 };
 
 __LIBC_HIDDEN__ extern WriteProtected<libc_globals> __libc_globals;
-// These cannot be in __libc_globals, because we cannot access the
+// This cannot be in __libc_globals, because we cannot access the
 // WriteProtected in a thread-safe way.
 // See b/328256432.
-//
-// __libc_memtag_stack says whether stack MTE is enabled on the process, i.e.
-// whether the stack pages are mapped with PROT_MTE. This is always false if
-// MTE is disabled for the process (i.e. libc_globals.memtag is false).
 __LIBC_HIDDEN__ extern _Atomic(bool) __libc_memtag_stack;
-// __libc_memtag_stack_abi says whether the process contains any code that was
-// compiled with memtag-stack. This is true even if the process does not have
-// MTE enabled (e.g. because it was overridden using MEMTAG_OPTIONS, or because
-// MTE is disabled for the device).
-// Code compiled with memtag-stack needs a stack history buffer in
-// TLS_SLOT_STACK_MTE, because the codegen will emit an unconditional
-// (to keep the code branchless) write to it.
-// Protected by g_heap_creation_lock.
-__LIBC_HIDDEN__ extern bool __libc_memtag_stack_abi;
 
 struct abort_msg_t;
 struct crash_detail_page_t;
@@ -146,9 +133,7 @@
   size_t scudo_stack_depot_size = 0;
 
   HeapTaggingLevel initial_heap_tagging_level = M_HEAP_TAGGING_LEVEL_NONE;
-  // See comments for __libc_memtag_stack / __libc_memtag_stack_abi above.
   bool initial_memtag_stack = false;
-  bool initial_memtag_stack_abi = false;
   int64_t heap_tagging_upgrade_timer_sec = 0;
 
   void (*memtag_stack_dlopen_callback)() = nullptr;