commit 8564b8d9e61580bef3bd5018cf63e37c78e40053
author Evgenii Stepanov <eugenis@google.com> Tue Dec 15 13:55:32 2020 -0800
committer Evgenii Stepanov <eugenis@google.com> Wed Jan 06 16:08:18 2021 -0800
tree 31105008dfcd942690f7143595121c2ab5d2bde8
parent dec48bdd9ee090f3b0e3ff22dcac4689a146e8d0

Use ELF notes to set the desired memory tagging level.

Use a note in executables to specify
(none|sync|async) heap tagging level. To be extended with (heap x stack x
globals) in the future. A missing note disables all tagging.

Bug: b/135772972
Test: bionic-unit-tests (in a future change)

Change-Id: Iab145a922c7abe24cdce17323f9e0c1063cc1321

libc/private/bionic_asm_arm64.h

diff --git a/libc/private/bionic_asm_arm64.h b/libc/private/bionic_asm_arm64.h
index c11732a..e73f25d 100644
--- a/libc/private/bionic_asm_arm64.h
+++ b/libc/private/bionic_asm_arm64.h
@@ -69,4 +69,10 @@
     .long (__bionic_asm_aarch64_feature_pac | \
            __bionic_asm_aarch64_feature_bti); \
     .long 0; \
-    .popsection; \
+    .popsection;
+
+#define NT_MEMTAG_LEVEL_MASK 3
+#define NT_MEMTAG_LEVEL_DEFAULT 0
+#define NT_MEMTAG_LEVEL_ASYNC 1
+#define NT_MEMTAG_LEVEL_SYNC 2
+#define NT_MEMTAG_HEAP 4

libc/private/bionic_asm_note.h

diff --git a/libc/private/bionic_asm_note.h b/libc/private/bionic_asm_note.h
index c335c5a..80b8f01 100644
--- a/libc/private/bionic_asm_note.h
+++ b/libc/private/bionic_asm_note.h
@@ -30,3 +30,4 @@
 
 #define NT_TYPE_IDENT 1
 #define NT_TYPE_KUSER 3
+#define NT_TYPE_MEMTAG 4

libc/private/bionic_globals.h

diff --git a/libc/private/bionic_globals.h b/libc/private/bionic_globals.h
index 5c9b726..8132261 100644
--- a/libc/private/bionic_globals.h
+++ b/libc/private/bionic_globals.h
@@ -41,6 +41,8 @@
 #include "private/bionic_vdso.h"
 #include "private/WriteProtected.h"
 
+#include <platform/bionic/malloc.h>
+
 struct libc_globals {
   vdso_entry vdso[VDSO_END];
   long setjmp_cookie;
@@ -106,6 +108,8 @@
 
   const char* scudo_stack_depot = nullptr;
   const char* scudo_region_info = nullptr;
+
+  HeapTaggingLevel initial_heap_tagging_level = M_HEAP_TAGGING_LEVEL_NONE;
 };
 
 __LIBC_HIDDEN__ libc_shared_globals* __libc_shared_globals();