Revert "Reset stack guard after fork from Zygote"

A performance regression was noticed in go/lem benchmarks for ART.  This
was likely caused by an issue in the related CL in the ART project.

Reason for revert: performance regression
Reverted Changes:
Ie0c81f97f:Remove stack protector from some interpreter funct...
Iaf565a374:Reset stack guard after fork from Zygote

Bug: 168258494
Change-Id: I1a415829b7714ad99014fbc67786c5608c81104c

core/jni/com_android_internal_os_Zygote.cpp

@@ -93,10 +93,6 @@
 
 #include "nativebridge/native_bridge.h"
 
-#if defined(__BIONIC__)
-extern "C" void android_reset_stack_guards();
-#endif
-
 namespace {
 
 // TODO (chriswailes): Add a function to initialize native Zygote data.
@@ -393,7 +389,6 @@ static void sendSigChildStatus(const pid_t pid, const uid_t uid, const int statu
 }
 
 // This signal handler is for zygote mode, since the zygote must reap its children
-NO_STACK_PROTECTOR
 static void SigChldHandler(int /*signal_number*/, siginfo_t* info, void* /*ucontext*/) {
     pid_t pid;
     int status;
@@ -1970,7 +1965,6 @@ void zygote::ZygoteFailure(JNIEnv* env,
 }
 
 // Utility routine to fork a process from the zygote.
-NO_STACK_PROTECTOR
 pid_t zygote::ForkCommon(JNIEnv* env, bool is_system_server,
                          const std::vector<int>& fds_to_close,
                          const std::vector<int>& fds_to_ignore,
@@ -2024,11 +2018,6 @@ pid_t zygote::ForkCommon(JNIEnv* env, bool is_system_server,
       setpriority(PRIO_PROCESS, 0, PROCESS_PRIORITY_MIN);
     }
 
-#if defined(__BIONIC__)
-    // Reset the stack guard for the new process.
-    android_reset_stack_guards();
-#endif
-
     // The child process.
     PreApplicationInit();
 
@@ -2061,7 +2050,6 @@ static void com_android_internal_os_Zygote_nativePreApplicationInit(JNIEnv*, jcl
   PreApplicationInit();
 }
 
-NO_STACK_PROTECTOR
 static jint com_android_internal_os_Zygote_nativeForkAndSpecialize(
         JNIEnv* env, jclass, jint uid, jint gid, jintArray gids, jint runtime_flags,
         jobjectArray rlimits, jint mount_external, jstring se_info, jstring nice_name,
@@ -2111,7 +2099,6 @@ static jint com_android_internal_os_Zygote_nativeForkAndSpecialize(
     return pid;
 }
 
-NO_STACK_PROTECTOR
 static jint com_android_internal_os_Zygote_nativeForkSystemServer(
         JNIEnv* env, jclass, uid_t uid, gid_t gid, jintArray gids,
         jint runtime_flags, jobjectArray rlimits, jlong permitted_capabilities,
@@ -2183,7 +2170,6 @@ static jint com_android_internal_os_Zygote_nativeForkSystemServer(
  * @param is_priority_fork  Controls the nice level assigned to the newly created process
  * @return child pid in the parent, 0 in the child
  */
-NO_STACK_PROTECTOR
 static jint com_android_internal_os_Zygote_nativeForkApp(JNIEnv* env,
                                                          jclass,
                                                          jint read_pipe_fd,
@@ -2198,7 +2184,6 @@ static jint com_android_internal_os_Zygote_nativeForkApp(JNIEnv* env,
                             args_known == JNI_TRUE, is_priority_fork == JNI_TRUE, true);
 }
 
-NO_STACK_PROTECTOR
 int zygote::forkApp(JNIEnv* env,
                     int read_pipe_fd,
                     int write_pipe_fd,

core/jni/com_android_internal_os_Zygote.h

@@ -20,14 +20,6 @@
 #define LOG_TAG "Zygote"
 #define ATRACE_TAG ATRACE_TAG_DALVIK
 
-/*
- * All functions that lead to ForkCommon must be marked with the
- * no_stack_protector attributed.  Because ForkCommon changes the stack
- * protector cookie, all of the guard checks on the frames above ForkCommon
- * would fail when they are popped.
- */
-#define NO_STACK_PROTECTOR __attribute__((no_stack_protector))
-
 #include <jni.h>
 #include <vector>
 #include <android-base/stringprintf.h>

core/jni/com_android_internal_os_ZygoteCommandBuffer.cpp

@@ -365,7 +365,6 @@ void com_android_internal_os_ZygoteCommandBuffer_nativeReadFullyAndReset(JNIEnv*
 // We only process fork commands if the peer uid matches expected_uid.
 // For every fork command after the first, we check that the requested uid is at
 // least minUid.
-NO_STACK_PROTECTOR
 jboolean com_android_internal_os_ZygoteCommandBuffer_nativeForkRepeatedly(
             JNIEnv* env,
             jclass,