From 990b5ec72182b117e34dce85a95868850daa7549 Mon Sep 17 00:00:00 2001
From: Colin Cross <ccross@android.com>
Date: Thu, 6 Jul 2023 16:17:01 -0700
Subject: [PATCH] Enable ptrace on userdebug when JDWP is disabled

r.android.com/2217921 disabled JDWP on userdebug builds by default in
order to avoid the JDWP overhead causing differences between user and
userdebug builds.  This had the side effect of disabling ptrace, which
means libmemunreachable can no longer ptrace app processes, and app
processes are no longer debuggable by gdbserver unless it is run as
root.

Add a new DEBUG_ENABLE_PTRACE zygote runtimeFlag for enabling ptrace,
and set it anywhere DEBUG_ENABLE_JDWP was set before
r.android.com/2217921.  Use the flag to call EnableDebugging.

Bug: 285967712
Test: adb shell dumpsys meminfo --unreachable com.android.gallery3d
Change-Id: I2fb1aa0aea81400f573b8c2e2fa309b7942d9446
---
 core/java/com/android/internal/os/Zygote.java             | 8 ++++++++
 core/jni/com_android_internal_os_Zygote.cpp               | 5 ++++-
 services/core/java/com/android/server/am/ProcessList.java | 1 +
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/core/java/com/android/internal/os/Zygote.java b/core/java/com/android/internal/os/Zygote.java
index d8aeb51c2e4d3..0786d6f87b679 100644
--- a/core/java/com/android/internal/os/Zygote.java
+++ b/core/java/com/android/internal/os/Zygote.java
@@ -195,6 +195,11 @@ public final class Zygote {
      */
     public static final int PROFILEABLE = 1 << 24;
 
+    /**
+     * Enable ptrace.  This is enabled on eng or userdebug builds, or if the app is debuggable.
+     */
+    public static final int DEBUG_ENABLE_PTRACE = 1 << 25;
+
     /** No external storage should be mounted. */
     public static final int MOUNT_EXTERNAL_NONE = IVold.REMOUNT_MODE_NONE;
     /** Default external storage should be mounted. */
@@ -1028,6 +1033,9 @@ public final class Zygote {
         if (Build.IS_ENG || ENABLE_JDWP) {
             args.mRuntimeFlags |= Zygote.DEBUG_ENABLE_JDWP;
         }
+        if (RoSystemProperties.DEBUGGABLE) {
+            args.mRuntimeFlags |= Zygote.DEBUG_ENABLE_PTRACE;
+        }
     }
 
     /**
diff --git a/core/jni/com_android_internal_os_Zygote.cpp b/core/jni/com_android_internal_os_Zygote.cpp
index a5d979ceade6d..bbaea0a457985 100644
--- a/core/jni/com_android_internal_os_Zygote.cpp
+++ b/core/jni/com_android_internal_os_Zygote.cpp
@@ -356,6 +356,7 @@ enum RuntimeFlags : uint32_t {
     GWP_ASAN_LEVEL_DEFAULT = 3 << 21,
     NATIVE_HEAP_ZERO_INIT_ENABLED = 1 << 23,
     PROFILEABLE = 1 << 24,
+    DEBUG_ENABLE_PTRACE = 1 << 25,
 };
 
 enum UnsolicitedZygoteMessageTypes : uint32_t {
@@ -1887,8 +1888,10 @@ static void SpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArray gids,
     }
 
     // Set process properties to enable debugging if required.
-    if ((runtime_flags & RuntimeFlags::DEBUG_ENABLE_JDWP) != 0) {
+    if ((runtime_flags & RuntimeFlags::DEBUG_ENABLE_PTRACE) != 0) {
         EnableDebugger();
+        // Don't pass unknown flag to the ART runtime.
+        runtime_flags &= ~RuntimeFlags::DEBUG_ENABLE_PTRACE;
     }
     if ((runtime_flags & RuntimeFlags::PROFILE_FROM_SHELL) != 0) {
         // simpleperf needs the process to be dumpable to profile it.
diff --git a/services/core/java/com/android/server/am/ProcessList.java b/services/core/java/com/android/server/am/ProcessList.java
index d0607d567900a..d1e744797fe9f 100644
--- a/services/core/java/com/android/server/am/ProcessList.java
+++ b/services/core/java/com/android/server/am/ProcessList.java
@@ -1741,6 +1741,7 @@ public final class ProcessList {
 
             if (debuggableFlag) {
                 runtimeFlags |= Zygote.DEBUG_ENABLE_JDWP;
+                runtimeFlags |= Zygote.DEBUG_ENABLE_PTRACE;
                 runtimeFlags |= Zygote.DEBUG_JAVA_DEBUGGABLE;
                 // Also turn on CheckJNI for debuggable apps. It's quite
                 // awkward to turn on otherwise.