commit e5e7395c9f59868909077b511572a24e597aa836
author Peter Collingbourne <pcc@google.com> Thu Dec 12 17:48:36 2019 -0800
committer Peter Collingbourne <pcc@google.com> Fri Dec 13 12:13:29 2019 -0800
tree 29688cbc15a122f23633e06f0014859abff87afc
parent b8c16c02e838675a61deb08fc6ac8c4173a0795f

Update bionic to use the MTE API proposed on LKML.

Patch set available here:
https://lore.kernel.org/linux-arm-kernel/20191211184027.20130-1-catalin.marinas@arm.com/
and in my android-experimental-mte branch.

Bug: 135772972
Change-Id: Ib46fd508330b330ef3afc713a9a4e26675ddb857

libc/bionic/libc_init_common.cpp

diff --git a/libc/bionic/libc_init_common.cpp b/libc/bionic/libc_init_common.cpp
index 542c4a5..d64a6bd 100644
--- a/libc/bionic/libc_init_common.cpp
+++ b/libc/bionic/libc_init_common.cpp
@@ -42,6 +42,7 @@
 #include <unistd.h>
 
 #include <async_safe/log.h>
+#include <platform/bionic/mte_kernel.h>
 
 #include "private/WriteProtected.h"
 #include "private/bionic_defs.h"
@@ -109,8 +110,18 @@
 #if defined(__aarch64__)
 #define PR_SET_TAGGED_ADDR_CTRL 55
 #define PR_TAGGED_ADDR_ENABLE   (1UL << 0)
+#ifdef ANDROID_EXPERIMENTAL_MTE
+  // First, try enabling MTE in asynchronous mode, with tag 0 excluded. This will fail if the kernel
+  // or hardware doesn't support MTE, and we will fall back to just enabling tagged pointers in
+  // syscall arguments.
+  if (prctl(PR_SET_TAGGED_ADDR_CTRL,
+            PR_TAGGED_ADDR_ENABLE | PR_MTE_TCF_ASYNC | (1 << PR_MTE_EXCL_SHIFT), 0, 0, 0)) {
+    prctl(PR_SET_TAGGED_ADDR_CTRL, PR_TAGGED_ADDR_ENABLE, 0, 0, 0);
+  }
+#else
   prctl(PR_SET_TAGGED_ADDR_CTRL, PR_TAGGED_ADDR_ENABLE, 0, 0, 0);
 #endif
+#endif
 }
 
 void __libc_init_fork_handler() {