Make fork equivalent to vfork when HWASan or MTE stack tagging is enabled.

Bug: 274056091
Change-Id: Iac029ca6b0e26f57f20c0a54822b75e3cae67344
diff --git a/libc/private/bionic_asm_offsets.h b/libc/private/bionic_asm_offsets.h
new file mode 100644
index 0000000..c2f2b56
--- /dev/null
+++ b/libc/private/bionic_asm_offsets.h
@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#pragma once
+
+#ifdef __aarch64__
+#define OFFSETOF_libc_globals_memtag_stack 80
+#endif
diff --git a/libc/private/bionic_globals.h b/libc/private/bionic_globals.h
index c375cc4..510d556 100644
--- a/libc/private/bionic_globals.h
+++ b/libc/private/bionic_globals.h
@@ -38,6 +38,7 @@
 
 #include "private/WriteProtected.h"
 #include "private/bionic_allocator.h"
+#include "private/bionic_asm_offsets.h"
 #include "private/bionic_elf_tls.h"
 #include "private/bionic_fdsan.h"
 #include "private/bionic_malloc_dispatch.h"
@@ -65,6 +66,10 @@
   MallocDispatch malloc_dispatch_table;
 };
 
+#ifdef __aarch64__
+static_assert(OFFSETOF_libc_globals_memtag_stack == offsetof(libc_globals, memtag_stack));
+#endif
+
 __LIBC_HIDDEN__ extern WriteProtected<libc_globals> __libc_globals;
 
 struct abort_msg_t;