From 8baf2c2b50883f3af497ca872fe6b435f3902444 Mon Sep 17 00:00:00 2001
From: Steven Moreland <smoreland@google.com>
Date: Fri, 16 Oct 2020 01:00:30 +0000
Subject: Zygote: disable heap 0'ing in apps.

Uninitialized memory back by popular demand.

We have trialed heap 0'ing (malloc is calloc) in Android for a few days
in all processes, but there are a couple of signs that doing this in app
processes may be too ambitious.

Bug: 170891666
Bug: 131355925

Test: boot, see disable logs
Change-Id: I60563712c8af459f2f847b4598477b042a05d7ea
---
 core/jni/com_android_internal_os_Zygote.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/core/jni/com_android_internal_os_Zygote.cpp b/core/jni/com_android_internal_os_Zygote.cpp
index dadf08f2cc90..95c295a4784c 100644
--- a/core/jni/com_android_internal_os_Zygote.cpp
+++ b/core/jni/com_android_internal_os_Zygote.cpp
@@ -80,6 +80,7 @@
 #include <bionic/mte.h>
 #include <bionic/mte_kernel.h>
 #include <cutils/fs.h>
+#include <cutils/memory.h>
 #include <cutils/multiuser.h>
 #include <cutils/sockets.h>
 #include <private/android_filesystem_config.h>
@@ -647,6 +648,13 @@ static void PreApplicationInit() {
 
   // Set the jemalloc decay time to 1.
   mallopt(M_DECAY_TIME, 1);
+
+  // Avoid potentially expensive memory mitigations, mostly meant for system
+  // processes, in apps. These may cause app compat problems, use more memory,
+  // or reduce performance. While it would be nice to have them for apps,
+  // we will have to wait until they are proven out, have more efficient
+  // hardware, and/or apply them only to new applications.
+  process_disable_memory_mitigations();
 }
 
 static void SetUpSeccompFilter(uid_t uid, bool is_child_zygote) {
-- 
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