From 15bdfea2165b0b384521182063c6018a1228c51a Mon Sep 17 00:00:00 2001
From: Ivan Lozano <ivanlozano@google.com>
Date: Fri, 14 Feb 2020 11:56:31 -0500
Subject: [PATCH] Remove execute-only memory related code.

The kernel no longer enforces XOM layouts, and the build system no
longer generates XOM binaries. As a result, the zygote code to mark XOM
sections of memory readable for apps with targetSdkVersion<Q.

Bug: 147300048
Test: m -j
Change-Id: I0abb0abb54f8f5a538da9194a900e6a64e574bfe
---
 core/java/com/android/internal/os/Zygote.java | 18 +---------
 .../android/internal/os/ZygoteConnection.java |  4 +--
 core/jni/com_android_internal_os_Zygote.cpp   | 33 -------------------
 3 files changed, 3 insertions(+), 52 deletions(-)

diff --git a/core/java/com/android/internal/os/Zygote.java b/core/java/com/android/internal/os/Zygote.java
index 556586477218a..94924a57e3f23 100644
--- a/core/java/com/android/internal/os/Zygote.java
+++ b/core/java/com/android/internal/os/Zygote.java
@@ -24,7 +24,6 @@ import android.content.pm.ApplicationInfo;
 import android.net.Credentials;
 import android.net.LocalServerSocket;
 import android.net.LocalSocket;
-import android.os.Build;
 import android.os.FactoryTest;
 import android.os.IVold;
 import android.os.Process;
@@ -291,7 +290,7 @@ public final class Zygote {
     static int forkAndSpecialize(int uid, int gid, int[] gids, int runtimeFlags,
             int[][] rlimits, int mountExternal, String seInfo, String niceName, int[] fdsToClose,
             int[] fdsToIgnore, boolean startChildZygote, String instructionSet, String appDataDir,
-            int targetSdkVersion, boolean isTopApp, String[] pkgDataInfoList) {
+            boolean isTopApp, String[] pkgDataInfoList) {
         ZygoteHooks.preFork();
 
         int pid = nativeForkAndSpecialize(
@@ -299,8 +298,6 @@ public final class Zygote {
                 fdsToIgnore, startChildZygote, instructionSet, appDataDir, isTopApp,
                 pkgDataInfoList);
         if (pid == 0) {
-            Zygote.disableExecuteOnly(targetSdkVersion);
-
             // Note that this event ends at the end of handleChildProc,
             Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "PostFork");
         }
@@ -696,8 +693,6 @@ public final class Zygote {
                                  args.mInstructionSet, args.mAppDataDir, args.mIsTopApp,
                                  args.mPkgDataInfoList);
 
-            disableExecuteOnly(args.mTargetSdkVersion);
-
             Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
 
             return ZygoteInit.zygoteInit(args.mTargetSdkVersion,
@@ -776,17 +771,6 @@ public final class Zygote {
         }
     }
 
-    /**
-     * Mark execute-only segments of libraries read+execute for apps with targetSdkVersion<Q.
-     */
-    private static void disableExecuteOnly(int targetSdkVersion) {
-        if ((targetSdkVersion < Build.VERSION_CODES.Q) && !nativeDisableExecuteOnly()) {
-            Log.e("Zygote", "Failed to set libraries to read+execute.");
-        }
-    }
-
-    private static native boolean nativeDisableExecuteOnly();
-
     /**
      * @return  Raw file descriptors for the read-end of USAP reporting pipes.
      */
diff --git a/core/java/com/android/internal/os/ZygoteConnection.java b/core/java/com/android/internal/os/ZygoteConnection.java
index c91c661b31de1..4949811bbe17f 100644
--- a/core/java/com/android/internal/os/ZygoteConnection.java
+++ b/core/java/com/android/internal/os/ZygoteConnection.java
@@ -257,8 +257,8 @@ class ZygoteConnection {
         pid = Zygote.forkAndSpecialize(parsedArgs.mUid, parsedArgs.mGid, parsedArgs.mGids,
                 parsedArgs.mRuntimeFlags, rlimits, parsedArgs.mMountExternal, parsedArgs.mSeInfo,
                 parsedArgs.mNiceName, fdsToClose, fdsToIgnore, parsedArgs.mStartChildZygote,
-                parsedArgs.mInstructionSet, parsedArgs.mAppDataDir, parsedArgs.mTargetSdkVersion,
-                parsedArgs.mIsTopApp, parsedArgs.mPkgDataInfoList);
+                parsedArgs.mInstructionSet, parsedArgs.mAppDataDir, parsedArgs.mIsTopApp,
+                parsedArgs.mPkgDataInfoList);
 
         try {
             if (pid == 0) {
diff --git a/core/jni/com_android_internal_os_Zygote.cpp b/core/jni/com_android_internal_os_Zygote.cpp
index 9fbb8df0d0792..9e578bfa8a648 100644
--- a/core/jni/com_android_internal_os_Zygote.cpp
+++ b/core/jni/com_android_internal_os_Zygote.cpp
@@ -49,7 +49,6 @@
 #include <fcntl.h>
 #include <grp.h>
 #include <inttypes.h>
-#include <link.h>
 #include <malloc.h>
 #include <mntent.h>
 #include <paths.h>
@@ -59,7 +58,6 @@
 #include <sys/capability.h>
 #include <sys/cdefs.h>
 #include <sys/eventfd.h>
-#include <sys/mman.h>
 #include <sys/personality.h>
 #include <sys/prctl.h>
 #include <sys/resource.h>
@@ -76,10 +74,8 @@
 #include <android-base/properties.h>
 #include <android-base/file.h>
 #include <android-base/stringprintf.h>
-#include <android-base/strings.h>
 #include <android-base/unique_fd.h>
 #include <bionic/malloc.h>
-#include <bionic/page.h>
 #include <cutils/fs.h>
 #include <cutils/multiuser.h>
 #include <cutils/sockets.h>
@@ -1905,25 +1901,6 @@ static void UnmountStorageOnInit(JNIEnv* env) {
   UnmountTree("/storage");
 }
 
-static int DisableExecuteOnly(struct dl_phdr_info* info,
-                              size_t size [[maybe_unused]],
-                              void* data [[maybe_unused]]) {
-  // Search for any execute-only segments and mark them read+execute.
-  for (int i = 0; i < info->dlpi_phnum; i++) {
-    const auto& phdr = info->dlpi_phdr[i];
-    if ((phdr.p_type == PT_LOAD) && (phdr.p_flags == PF_X)) {
-      auto addr = reinterpret_cast<void*>(info->dlpi_addr + PAGE_START(phdr.p_vaddr));
-      size_t len = PAGE_OFFSET(phdr.p_vaddr) + phdr.p_memsz;
-      if (mprotect(addr, len, PROT_READ | PROT_EXEC) == -1) {
-        ALOGE("mprotect(%p, %zu, PROT_READ | PROT_EXEC) failed: %m", addr, len);
-        return -1;
-      }
-    }
-  }
-  // Return non-zero to exit dl_iterate_phdr.
-  return 0;
-}
-
 }  // anonymous namespace
 
 namespace android {
@@ -2286,14 +2263,6 @@ static void com_android_internal_os_Zygote_nativeEmptyUsapPool(JNIEnv* env, jcla
   }
 }
 
-/**
- * @param env  Managed runtime environment
- * @return  True if disable was successful.
- */
-static jboolean com_android_internal_os_Zygote_nativeDisableExecuteOnly(JNIEnv* env, jclass) {
-  return dl_iterate_phdr(DisableExecuteOnly, nullptr) == 0;
-}
-
 static void com_android_internal_os_Zygote_nativeBlockSigTerm(JNIEnv* env, jclass) {
   auto fail_fn = std::bind(ZygoteFailure, env, "usap", nullptr, _1);
   BlockSignal(SIGTERM, fail_fn);
@@ -2375,8 +2344,6 @@ static const JNINativeMethod gMethods[] = {
         {"nativeGetUsapPoolCount", "()I",
          (void*)com_android_internal_os_Zygote_nativeGetUsapPoolCount},
         {"nativeEmptyUsapPool", "()V", (void*)com_android_internal_os_Zygote_nativeEmptyUsapPool},
-        {"nativeDisableExecuteOnly", "()Z",
-         (void*)com_android_internal_os_Zygote_nativeDisableExecuteOnly},
         {"nativeBlockSigTerm", "()V", (void*)com_android_internal_os_Zygote_nativeBlockSigTerm},
         {"nativeUnblockSigTerm", "()V", (void*)com_android_internal_os_Zygote_nativeUnblockSigTerm},
         {"nativeBoostUsapPriority", "()V",