[MTE] Enable ASYNC MTE in the Zygote.

This allows applications to turn on MTE. The current design of MTE
inside of Scudo doesn't allow us to late-enable MTE (but we can
late-disable it). Thus, we have to enable tagging in the Zygote in order
to allow apps and the system_server to control their own MTE behaviour.

We intentionally use ASYNC mode so that we don't waste memory collecting
stack traces from the zygote pre-fork. Given that the zygote is mostly
Java code, the process itself should be pretty low risk for memory
corruption.

Bug: 135772972
Bug: 172365548
Test: On FVP: atest -s localhost:5555 \
com.android.cts.tagging.TaggingSdk30Test#testMemoryTagChecksCompatFeatureEnabled \
com.android.cts.tagging.TaggingSdk30Test#testMemoryTagChecksCompatFeatureDisabled

Change-Id: I9da2c33cb6022033264f443308d5508b3ff8da9e

1 files changed, 9 insertions, 0 deletions

diff --git a/cmds/app_process/Android.bp b/cmds/app_process/Android.bp
index 07221f97c72b..14ebb713b6ae 100644
--- a/cmds/app_process/Android.bp
+++ b/cmds/app_process/Android.bp
@@ -62,4 +62,13 @@ cc_binary {
     // Create a symlink from app_process to app_process32 or 64
     // depending on the target configuration.
     symlink_preferred_arch: true,
+
+    // Enable ASYNC MTE in the zygote, in order to allow apps and the system
+    // server to use MTE. We use ASYNC because we don't expect the pre-fork
+    // zygote to have substantial memory corruption bugs (as it's primarily Java
+    // code), and we don't want to waste memory recording malloc/free stack
+    // traces (which happens in SYNC mode).
+    sanitize: {
+        memtag_heap: true,
+    },
 }