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gecko-dev/mozglue/build/Nuwa.cpp

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
* You can obtain one at http://mozilla.org/MPL/2.0/. */
#include <map>
#include <memory>
#include <dlfcn.h>
#include <errno.h>
#include <fcntl.h>
#include <setjmp.h>
#include <signal.h>
#include <poll.h>
#include <pthread.h>
#include <alloca.h>
#include <sys/epoll.h>
#include <sys/mman.h>
#include <sys/prctl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <vector>
#include "mozilla/LinkedList.h"
#include "mozilla/TaggedAnonymousMemory.h"
#include "Nuwa.h"
using namespace mozilla;
/**
* Provides the wrappers to a selected set of pthread and system-level functions
* as the basis for implementing Zygote-like preforking mechanism.
*/
/**
* Real functions for the wrappers.
*/
extern "C" {
#pragma GCC visibility push(default)
int __real_pthread_create(pthread_t *thread,
const pthread_attr_t *attr,
void *(*start_routine) (void *),
void *arg);
int __real_pthread_key_create(pthread_key_t *key, void (*destructor)(void*));
int __real_pthread_key_delete(pthread_key_t key);
pthread_t __real_pthread_self();
int __real_pthread_join(pthread_t thread, void **retval);
int __real_epoll_wait(int epfd,
struct epoll_event *events,
int maxevents,
int timeout);
int __real_pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mtx);
int __real_pthread_cond_timedwait(pthread_cond_t *cond,
pthread_mutex_t *mtx,
const struct timespec *abstime);
int __real_pthread_mutex_lock(pthread_mutex_t *mtx);
int __real_poll(struct pollfd *fds, nfds_t nfds, int timeout);
int __real_epoll_create(int size);
int __real_socketpair(int domain, int type, int protocol, int sv[2]);
int __real_pipe2(int __pipedes[2], int flags);
int __real_pipe(int __pipedes[2]);
int __real_epoll_ctl(int aEpollFd, int aOp, int aFd, struct epoll_event *aEvent);
int __real_close(int aFd);
#pragma GCC visibility pop
}
#define REAL(s) __real_##s
/**
* A Nuwa process is started by preparing. After preparing, it waits
* for all threads becoming frozen. Then, it is ready while all
* threads are frozen.
*/
static bool sIsNuwaProcess = false; // This process is a Nuwa process.
static bool sIsFreezing = false; // Waiting for all threads getting frozen.
static bool sNuwaReady = false; // Nuwa process is ready.
static bool sNuwaPendingSpawn = false; // Are there any pending spawn requests?
static bool sNuwaForking = false;
// Fds of transports of top level protocols.
static NuwaProtoFdInfo sProtoFdInfos[NUWA_TOPLEVEL_MAX];
static int sProtoFdInfosSize = 0;
typedef std::vector<std::pair<pthread_key_t, void *> >
TLSInfoList;
/**
* Return the system's page size
*/
static size_t getPageSize(void) {
#ifdef HAVE_GETPAGESIZE
return getpagesize();
#elif defined(_SC_PAGESIZE)
return sysconf(_SC_PAGESIZE);
#elif defined(PAGE_SIZE)
return PAGE_SIZE;
#else
#warning "Hard-coding page size to 4096 bytes"
return 4096
#endif
}
/**
* The stack size is chosen carefully so the frozen threads doesn't consume too
* much memory in the Nuwa process. The threads shouldn't run deep recursive
* methods or do large allocations on the stack to avoid stack overflow.
*/
#ifndef NUWA_STACK_SIZE
#define NUWA_STACK_SIZE (1024 * 128)
#endif
#define NATIVE_THREAD_NAME_LENGTH 16
typedef struct nuwa_construct {
typedef void(*construct_t)(void*);
construct_t construct;
void *arg;
nuwa_construct(construct_t aConstruct, void *aArg)
: construct(aConstruct)
, arg(aArg)
{ }
nuwa_construct(const nuwa_construct&) = default;
nuwa_construct& operator=(const nuwa_construct&) = default;
} nuwa_construct_t;
struct thread_info : public mozilla::LinkedListElement<thread_info> {
pthread_t origThreadID;
pthread_t recreatedThreadID;
pthread_attr_t threadAttr;
jmp_buf jmpEnv;
jmp_buf retEnv;
int flags;
void *(*startupFunc)(void *arg);
void *startupArg;
// The thread specific function to recreate the new thread. It's executed
// after the thread is recreated.
std::vector<nuwa_construct_t> *recrFunctions;
void addThreadConstructor(const nuwa_construct_t *construct) {
if (!recrFunctions) {
recrFunctions = new std::vector<nuwa_construct_t>();
}
recrFunctions->push_back(*construct);
}
TLSInfoList tlsInfo;
/**
* We must ensure that the recreated thread has entered pthread_cond_wait() or
* similar functions before proceeding to recreate the next one. Otherwise, if
* the next thread depends on the same mutex, it may be used in an incorrect
* state. To do this, the main thread must unconditionally acquire the mutex.
* The mutex is unconditionally released when the recreated thread enters
* pthread_cond_wait(). The recreated thread may have locked the mutex itself
* (if the pthread_mutex_trylock succeeded) or another thread may have already
* held the lock. If the recreated thread did lock the mutex we must balance
* that with another unlock on the main thread, which is signaled by
* condMutexNeedsBalancing.
*/
pthread_mutex_t *condMutex;
bool condMutexNeedsBalancing;
void *stk;
pid_t origNativeThreadID;
pid_t recreatedNativeThreadID;
char nativeThreadName[NATIVE_THREAD_NAME_LENGTH];
};
typedef struct thread_info thread_info_t;
static thread_info_t *sCurrentRecreatingThread = nullptr;
/**
* This function runs the custom recreation function registered when calling
* NuwaMarkCurrentThread() after thread stack is restored.
*/
static void
RunCustomRecreation() {
thread_info_t *tinfo = sCurrentRecreatingThread;
if (tinfo->recrFunctions) {
for (auto iter = tinfo->recrFunctions->begin();
iter != tinfo->recrFunctions->end();
iter++) {
iter->construct(iter->arg);
}
}
}
/**
* Every thread should be marked as either TINFO_FLAG_NUWA_SUPPORT or
* TINFO_FLAG_NUWA_SKIP, or it means a potential error. We force
* Gecko code to mark every single thread to make sure there are no accidents
* when recreating threads with Nuwa.
*
* Threads marked as TINFO_FLAG_NUWA_SUPPORT can be checkpointed explicitly, by
* calling NuwaCheckpointCurrentThread(), or implicitly when they call into wrapped
* functions like pthread_mutex_lock(), epoll_wait(), etc.
* TINFO_FLAG_NUWA_EXPLICIT_CHECKPOINT denotes the explicitly checkpointed thread.
*/
#define TINFO_FLAG_NUWA_SUPPORT 0x1
#define TINFO_FLAG_NUWA_SKIP 0x2
#define TINFO_FLAG_NUWA_EXPLICIT_CHECKPOINT 0x4
static std::vector<nuwa_construct_t> sConstructors;
static std::vector<nuwa_construct_t> sFinalConstructors;
typedef std::map<pthread_key_t, void (*)(void *)> TLSKeySet;
static TLSKeySet sTLSKeys;
/**
* This mutex is used to block the running threads and freeze their contexts.
* PrepareNuwaProcess() is the first one to acquire the lock. Further attempts
* to acquire this mutex (in the freeze point macros) will block and freeze the
* calling thread.
*/
static pthread_mutex_t sThreadFreezeLock = PTHREAD_MUTEX_INITIALIZER;
static thread_info_t sMainThread;
static int sThreadCount = 0;
static int sThreadFreezeCount = 0;
// Bug 1008254: LinkedList's destructor asserts that the list is empty.
// But here, on exit, when the global sAllThreads list
// is destroyed, it may or may be empty. Bug 1008254 comment 395 has a log
// when there were 8 threads remaining on exit. So this assertion was
// intermittently (almost every second time) failing.
// As a work-around to avoid this intermittent failure, we clear the list on
// exit just before it gets destroyed. This is the only purpose of that
// AllThreadsListType subclass.
struct AllThreadsListType : public LinkedList<thread_info_t>
{
~AllThreadsListType()
{
if (!isEmpty()) {
__android_log_print(ANDROID_LOG_WARN, "Nuwa",
"Threads remaining at exit:\n");
int n = 0;
for (const thread_info_t* t = getFirst(); t; t = t->getNext()) {
__android_log_print(ANDROID_LOG_WARN, "Nuwa",
" %.*s (origNativeThreadID=%d recreatedNativeThreadID=%d)\n",
NATIVE_THREAD_NAME_LENGTH,
t->nativeThreadName,
t->origNativeThreadID,
t->recreatedNativeThreadID);
n++;
}
__android_log_print(ANDROID_LOG_WARN, "Nuwa",
"total: %d outstanding threads. "
"Please fix them so they're destroyed before this point!\n", n);
__android_log_print(ANDROID_LOG_WARN, "Nuwa",
"note: sThreadCount=%d, sThreadFreezeCount=%d\n",
sThreadCount,
sThreadFreezeCount);
}
clear();
}
};
static AllThreadsListType sAllThreads;
/**
* This mutex protects the access to thread info:
* sAllThreads, sThreadCount, sThreadFreezeCount, sRecreateVIPCount.
*/
static pthread_mutex_t sThreadCountLock = PTHREAD_MUTEX_INITIALIZER;
/**
* This condition variable lets MakeNuwaProcess() wait until all recreated
* threads are frozen.
*/
static pthread_cond_t sThreadChangeCond = PTHREAD_COND_INITIALIZER;
/**
* This mutex and condition variable is used to serialize the fork requests
* from the parent process.
*/
static pthread_mutex_t sForkLock = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t sForkWaitCond = PTHREAD_COND_INITIALIZER;
/**
* sForkWaitCondChanged will be reset to false on the IPC thread before
* and will be changed to true on the main thread to indicate that the condition
* that the IPC thread is waiting for has already changed.
*/
static bool sForkWaitCondChanged = false;
/**
* This mutex protects the access to sTLSKeys, which keeps track of existing
* TLS Keys.
*/
static pthread_mutex_t sTLSKeyLock = PTHREAD_MUTEX_INITIALIZER;
static int sThreadSkipCount = 0;
static thread_info_t *
GetThreadInfoInner(pthread_t threadID) {
for (thread_info_t *tinfo = sAllThreads.getFirst();
tinfo;
tinfo = tinfo->getNext()) {
if (pthread_equal(tinfo->origThreadID, threadID)) {
return tinfo;
}
}
return nullptr;
}
/**
* Get thread info using the specified thread ID.
*
* @return thread_info_t which has threadID == specified threadID
*/
static thread_info_t *
GetThreadInfo(pthread_t threadID) {
if (sIsNuwaProcess) {
REAL(pthread_mutex_lock)(&sThreadCountLock);
}
thread_info_t *tinfo = GetThreadInfoInner(threadID);
if (sIsNuwaProcess) {
pthread_mutex_unlock(&sThreadCountLock);
}
return tinfo;
}
#if !defined(HAVE_THREAD_TLS_KEYWORD)
/**
* Get thread info of the current thread.
*
* @return thread_info_t for the current thread.
*/
static thread_info_t *
GetCurThreadInfo() {
pthread_t threadID = REAL(pthread_self)();
pthread_t thread_info_t::*threadIDptr =
(sIsNuwaProcess ?
&thread_info_t::origThreadID :
&thread_info_t::recreatedThreadID);
REAL(pthread_mutex_lock)(&sThreadCountLock);
thread_info_t *tinfo;
for (tinfo = sAllThreads.getFirst();
tinfo;
tinfo = tinfo->getNext()) {
if (pthread_equal(tinfo->*threadIDptr, threadID)) {
break;
}
}
pthread_mutex_unlock(&sThreadCountLock);
return tinfo;
}
#define CUR_THREAD_INFO GetCurThreadInfo()
#define SET_THREAD_INFO(x) /* Nothing to do. */
#else
// Is not nullptr only for threads created by pthread_create() in an Nuwa process.
// It is always nullptr for the main thread.
static __thread thread_info_t *sCurThreadInfo = nullptr;
#define CUR_THREAD_INFO sCurThreadInfo
#define SET_THREAD_INFO(x) do { sCurThreadInfo = (x); } while(0)
#endif // HAVE_THREAD_TLS_KEYWORD
/*
* Track all epoll fds and handling events.
*/
class EpollManager {
public:
class EpollInfo {
public:
typedef struct epoll_event Events;
typedef std::map<int, Events> EpollEventsMap;
typedef EpollEventsMap::iterator iterator;
typedef EpollEventsMap::const_iterator const_iterator;
EpollInfo(): mBackSize(0) {}
EpollInfo(int aBackSize): mBackSize(aBackSize) {}
EpollInfo(const EpollInfo &aOther): mEvents(aOther.mEvents)
, mBackSize(aOther.mBackSize) {
}
~EpollInfo() {
mEvents.clear();
}
void AddEvents(int aFd, Events &aEvents) {
std::pair<iterator, bool> pair =
mEvents.insert(std::make_pair(aFd, aEvents));
if (!pair.second) {
abort();
}
}
void RemoveEvents(int aFd) {
if (!mEvents.erase(aFd)) {
abort();
}
}
void ModifyEvents(int aFd, Events &aEvents) {
iterator it = mEvents.find(aFd);
if (it == mEvents.end()) {
abort();
}
it->second = aEvents;
}
const Events &FindEvents(int aFd) const {
const_iterator it = mEvents.find(aFd);
if (it == mEvents.end()) {
abort();
}
return it->second;
}
int Size() const { return mEvents.size(); }
// Iterator with values of <fd, Events> pairs.
const_iterator begin() const { return mEvents.begin(); }
const_iterator end() const { return mEvents.end(); }
int BackSize() const { return mBackSize; }
private:
EpollEventsMap mEvents;
int mBackSize;
friend class EpollManager;
};
typedef std::map<int, EpollInfo> EpollInfoMap;
typedef EpollInfoMap::iterator iterator;
typedef EpollInfoMap::const_iterator const_iterator;
public:
void AddEpollInfo(int aEpollFd, int aBackSize) {
EpollInfo *oldinfo = FindEpollInfo(aEpollFd);
if (oldinfo != nullptr) {
abort();
}
mEpollFdsInfo[aEpollFd] = EpollInfo(aBackSize);
}
EpollInfo *FindEpollInfo(int aEpollFd) {
iterator it = mEpollFdsInfo.find(aEpollFd);
if (it == mEpollFdsInfo.end()) {
return nullptr;
}
return &it->second;
}
void RemoveEpollInfo(int aEpollFd) {
if (!mEpollFdsInfo.erase(aEpollFd)) {
abort();
}
}
int Size() const { return mEpollFdsInfo.size(); }
// Iterator of <epollfd, EpollInfo> pairs.
const_iterator begin() const { return mEpollFdsInfo.begin(); }
const_iterator end() const { return mEpollFdsInfo.end(); }
static EpollManager *Singleton() {
if (!sInstance) {
sInstance = new EpollManager();
}
return sInstance;
}
static void Shutdown() {
if (!sInstance) {
abort();
}
delete sInstance;
sInstance = nullptr;
}
private:
static EpollManager *sInstance;
~EpollManager() {
mEpollFdsInfo.clear();
}
EpollInfoMap mEpollFdsInfo;
EpollManager() {}
};
EpollManager* EpollManager::sInstance;
static thread_info_t *
thread_info_new(void) {
/* link tinfo to sAllThreads */
thread_info_t *tinfo = new thread_info_t();
tinfo->flags = 0;
tinfo->recrFunctions = nullptr;
tinfo->recreatedThreadID = 0;
tinfo->recreatedNativeThreadID = 0;
tinfo->condMutex = nullptr;
tinfo->condMutexNeedsBalancing = false;
tinfo->stk = MozTaggedAnonymousMmap(nullptr,
NUWA_STACK_SIZE + getPageSize(),
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS,
/* fd */ -1,
/* offset */ 0,
"nuwa-thread-stack");
// We use a smaller stack size. Add protection to stack overflow: mprotect()
// stack top (the page at the lowest address) so we crash instead of corrupt
// other content that is malloc()'d.
mprotect(tinfo->stk, getPageSize(), PROT_NONE);
pthread_attr_init(&tinfo->threadAttr);
REAL(pthread_mutex_lock)(&sThreadCountLock);
// Insert to the tail.
sAllThreads.insertBack(tinfo);
sThreadCount++;
pthread_cond_signal(&sThreadChangeCond);
pthread_mutex_unlock(&sThreadCountLock);
return tinfo;
}
static void
thread_info_cleanup(void *arg) {
if (sNuwaForking) {
// We shouldn't have any thread exiting when we are forking a new process.
abort();
}
thread_info_t *tinfo = (thread_info_t *)arg;
pthread_attr_destroy(&tinfo->threadAttr);
munmap(tinfo->stk, NUWA_STACK_SIZE + getPageSize());
REAL(pthread_mutex_lock)(&sThreadCountLock);
/* unlink tinfo from sAllThreads */
tinfo->remove();
pthread_mutex_unlock(&sThreadCountLock);
if (tinfo->recrFunctions) {
delete tinfo->recrFunctions;
}
// while sThreadCountLock is held, since delete calls wrapped functions
// which try to lock sThreadCountLock. This results in deadlock. And we
// need to delete |tinfo| before decreasing sThreadCount, so Nuwa won't
// get ready before tinfo is cleaned.
delete tinfo;
REAL(pthread_mutex_lock)(&sThreadCountLock);
sThreadCount--;
pthread_cond_signal(&sThreadChangeCond);
pthread_mutex_unlock(&sThreadCountLock);
}
static void*
cleaner_thread(void *arg) {
thread_info_t *tinfo = (thread_info_t *)arg;
pthread_t *thread = sIsNuwaProcess ? &tinfo->origThreadID
: &tinfo->recreatedThreadID;
// Wait until target thread end.
while (!pthread_kill(*thread, 0)) {
sched_yield();
}
thread_info_cleanup(tinfo);
return nullptr;
}
static void
thread_cleanup(void *arg) {
pthread_t thread;
REAL(pthread_create)(&thread, nullptr, &cleaner_thread, arg);
pthread_detach(thread);
}
static void *
_thread_create_startup(void *arg) {
thread_info_t *tinfo = (thread_info_t *)arg;
void *r;
// Save thread info; especially, stackaddr & stacksize.
// Reuse the stack in the new thread.
pthread_getattr_np(REAL(pthread_self)(), &tinfo->threadAttr);
SET_THREAD_INFO(tinfo);
tinfo->origThreadID = REAL(pthread_self)();
tinfo->origNativeThreadID = gettid();
pthread_cleanup_push(thread_cleanup, tinfo);
r = tinfo->startupFunc(tinfo->startupArg);
if (!sIsNuwaProcess) {
return r;
}
pthread_cleanup_pop(1);
return r;
}
// reserve STACK_RESERVED_SZ * 4 bytes for thread_recreate_startup().
#define STACK_RESERVED_SZ 64
#define STACK_SENTINEL(v) ((v)[0])
#define STACK_SENTINEL_VALUE(v) ((uint32_t)(v) ^ 0xdeadbeef)
static void *
thread_create_startup(void *arg) {
/*
* Dark Art!! Never try to do the same unless you are ABSOLUTELY sure of
* what you are doing!
*
* This function is here for reserving stack space before calling
* _thread_create_startup(). see also thread_create_startup();
*/
void *r;
volatile uint32_t reserved[STACK_RESERVED_SZ];
// Reserve stack space.
STACK_SENTINEL(reserved) = STACK_SENTINEL_VALUE(reserved);
r = _thread_create_startup(arg);
// Check if the reservation is enough.
if (STACK_SENTINEL(reserved) != STACK_SENTINEL_VALUE(reserved)) {
abort(); // Did not reserve enough stack space.
}
thread_info_t *tinfo = CUR_THREAD_INFO;
if (!sIsNuwaProcess) {
longjmp(tinfo->retEnv, 1);
// Never go here!
abort();
}
return r;
}
extern "C" MFBT_API int
__wrap_pthread_create(pthread_t *thread,
const pthread_attr_t *attr,
void *(*start_routine) (void *),
void *arg) {
if (!sIsNuwaProcess) {
return REAL(pthread_create)(thread, attr, start_routine, arg);
}
thread_info_t *tinfo = thread_info_new();
tinfo->startupFunc = start_routine;
tinfo->startupArg = arg;
pthread_attr_setstack(&tinfo->threadAttr,
(char*)tinfo->stk + getPageSize(),
NUWA_STACK_SIZE);
int rv = REAL(pthread_create)(thread,
&tinfo->threadAttr,
thread_create_startup,
tinfo);
if (rv) {
thread_info_cleanup(tinfo);
} else {
tinfo->origThreadID = *thread;
}
return rv;
}
// TLS related
/**
* Iterates over the existing TLS keys and store the TLS data for the current
* thread in tinfo.
*/
static void
SaveTLSInfo(thread_info_t *tinfo) {
REAL(pthread_mutex_lock)(&sTLSKeyLock);
tinfo->tlsInfo.clear();
for (TLSKeySet::const_iterator it = sTLSKeys.begin();
it != sTLSKeys.end();
it++) {
void *value = pthread_getspecific(it->first);
if (value == nullptr) {
continue;
}
pthread_key_t key = it->first;
tinfo->tlsInfo.push_back(TLSInfoList::value_type(key, value));
}
pthread_mutex_unlock(&sTLSKeyLock);
}
/**
* Restores the TLS data for the current thread from tinfo.
*/
static void
RestoreTLSInfo(thread_info_t *tinfo) {
for (TLSInfoList::const_iterator it = tinfo->tlsInfo.begin();
it != tinfo->tlsInfo.end();
it++) {
pthread_key_t key = it->first;
const void *value = it->second;
if (pthread_setspecific(key, value)) {
abort();
}
}
SET_THREAD_INFO(tinfo);
tinfo->recreatedThreadID = REAL(pthread_self)();
tinfo->recreatedNativeThreadID = gettid();
}
extern "C" MFBT_API int
__wrap_pthread_key_create(pthread_key_t *key, void (*destructor)(void*)) {
int rv = REAL(pthread_key_create)(key, destructor);
if (rv != 0) {
return rv;
}
REAL(pthread_mutex_lock)(&sTLSKeyLock);
sTLSKeys.insert(TLSKeySet::value_type(*key, destructor));
pthread_mutex_unlock(&sTLSKeyLock);
return 0;
}
extern "C" MFBT_API int
__wrap_pthread_key_delete(pthread_key_t key) {
if (!sIsNuwaProcess) {
return REAL(pthread_key_delete)(key);
}
int rv = REAL(pthread_key_delete)(key);
if (rv != 0) {
return rv;
}
REAL(pthread_mutex_lock)(&sTLSKeyLock);
sTLSKeys.erase(key);
pthread_mutex_unlock(&sTLSKeyLock);
return 0;
}
extern "C" MFBT_API pthread_t
__wrap_pthread_self() {
thread_info_t *tinfo = CUR_THREAD_INFO;
if (tinfo) {
// For recreated thread, masquerade as the original thread in the Nuwa
// process.
return tinfo->origThreadID;
}
return REAL(pthread_self)();
}
extern "C" MFBT_API int
__wrap_pthread_join(pthread_t thread, void **retval) {
thread_info_t *tinfo = GetThreadInfo(thread);
if (tinfo == nullptr) {
return REAL(pthread_join)(thread, retval);
}
// pthread_join() need to use the real thread ID in the spawned process.
return REAL(pthread_join)(tinfo->recreatedThreadID, retval);
}
/**
* The following are used to synchronize between the main thread and the
* thread being recreated. The main thread will wait until the thread is woken
* up from the freeze points or the blocking intercepted functions and then
* proceed to recreate the next frozen thread.
*
* In thread recreation, the main thread recreates the frozen threads one by
* one. The recreated threads will be "gated" until the main thread "opens the
* gate" to let them run freely as if they were created from scratch. The VIP
* threads gets the chance to run first after their thread stacks are recreated
* (using longjmp()) so they can adjust their contexts to a valid, consistent
* state. The threads frozen waiting for pthread condition variables are VIP
* threads. After woken up they need to run first to make the associated mutex
* in a valid state to maintain the semantics of the intercepted function calls
* (like pthread_cond_wait()).
*/
// Used to synchronize the main thread and the thread being recreated so that
// only one thread is allowed to be recreated at a time.
static pthread_mutex_t sRecreateWaitLock = PTHREAD_MUTEX_INITIALIZER;
// Used to block recreated threads until the main thread "opens the gate".
static pthread_mutex_t sRecreateGateLock = PTHREAD_MUTEX_INITIALIZER;
// Used to block the main thread from "opening the gate" until all VIP threads
// have been recreated.
static pthread_mutex_t sRecreateVIPGateLock = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t sRecreateVIPCond = PTHREAD_COND_INITIALIZER;
static int sRecreateVIPCount = 0;
static int sRecreateGatePassed = 0;
/**
* Thread recreation macros.
*
* The following macros are used in the forked process to synchronize and
* control the progress of thread recreation.
*
* 1. RECREATE_START() is first called in the beginning of thread
* recreation to set sRecreateWaitLock and sRecreateGateLock in locked
* state.
* 2. For each frozen thread:
* 2.1. RECREATE_BEFORE() to set the thread being recreated.
* 2.2. thread_recreate() to recreate the frozen thread.
* 2.3. Main thread calls RECREATE_WAIT() to wait on sRecreateWaitLock until
* the thread is recreated from the freeze point and calls
* RECREATE_CONTINUE() to release sRecreateWaitLock.
* 2.3. Non-VIP threads are blocked on RECREATE_GATE(). VIP threads calls
* RECREATE_PASS_VIP() to mark that a VIP thread is successfully
* recreated and then is blocked by calling RECREATE_GATE_VIP().
* 3. RECREATE_WAIT_ALL_VIP() to wait until all VIP threads passed, that is,
* VIP threads already has their contexts (mainly pthread mutex) in a valid
* state.
* 4. RECREATE_OPEN_GATE() to unblock threads blocked by sRecreateGateLock.
* 5. RECREATE_FINISH() to complete thread recreation.
*/
#define RECREATE_START() \
do { \
REAL(pthread_mutex_lock)(&sRecreateWaitLock); \
REAL(pthread_mutex_lock)(&sRecreateGateLock); \
} while(0)
#define RECREATE_BEFORE(info) do { sCurrentRecreatingThread = info; } while(0)
#define RECREATE_WAIT() REAL(pthread_mutex_lock)(&sRecreateWaitLock)
#define RECREATE_CONTINUE() do { \
RunCustomRecreation(); \
pthread_mutex_unlock(&sRecreateWaitLock); \
} while(0)
#define RECREATE_FINISH() pthread_mutex_unlock(&sRecreateWaitLock)
#define RECREATE_GATE() \
do { \
REAL(pthread_mutex_lock)(&sRecreateGateLock); \
sRecreateGatePassed++; \
pthread_mutex_unlock(&sRecreateGateLock); \
} while(0)
#define RECREATE_OPEN_GATE() pthread_mutex_unlock(&sRecreateGateLock)
#define RECREATE_GATE_VIP() \
do { \
REAL(pthread_mutex_lock)(&sRecreateGateLock); \
pthread_mutex_unlock(&sRecreateGateLock); \
} while(0)
#define RECREATE_PASS_VIP() \
do { \
REAL(pthread_mutex_lock)(&sRecreateVIPGateLock); \
sRecreateGatePassed++; \
pthread_cond_signal(&sRecreateVIPCond); \
pthread_mutex_unlock(&sRecreateVIPGateLock); \
} while(0)
#define RECREATE_WAIT_ALL_VIP() \
do { \
REAL(pthread_mutex_lock)(&sRecreateVIPGateLock); \
while(sRecreateGatePassed < sRecreateVIPCount) { \
REAL(pthread_cond_wait)(&sRecreateVIPCond, \
&sRecreateVIPGateLock); \
} \
pthread_mutex_unlock(&sRecreateVIPGateLock); \
} while(0)
/**
* Thread freeze points. Note that the freeze points are implemented as macros
* so as not to garble the content of the stack after setjmp().
*
* In the nuwa process, when a thread supporting nuwa calls a wrapper
* function, freeze point 1 setjmp()s to save the state. We only allow the
* thread to be frozen in the wrapper functions. If thread freezing is not
* enabled yet, the wrapper functions act like their wrapped counterparts,
* except for the extra actions in the freeze points. If thread freezing is
* enabled, the thread will be frozen by calling one of the wrapper functions.
* The threads can be frozen in any of the following points:
*
* 1) Freeze point 1: this is the point where we setjmp() in the nuwa process
* and longjmp() in the spawned process. If freezing is enabled, then the
* current thread blocks by acquiring an already locked mutex,
* sThreadFreezeLock.
* 2) The wrapped function: the function that might block waiting for some
* resource or condition.
* 3) Freeze point 2: blocks the current thread by acquiring sThreadFreezeLock.
* If freezing is not enabled then revert the counter change in freeze
* point 1.
*
* Note: the purpose of the '(void) variable;' statements is to avoid
* -Wunused-but-set-variable warnings.
*/
#define THREAD_FREEZE_POINT1() \
bool freezeCountChg = false; \
bool recreated = false; \
(void) recreated; \
volatile bool freezePoint2 = false; \
(void) freezePoint2; \
thread_info_t *tinfo; \
if (sIsNuwaProcess && \
(tinfo = CUR_THREAD_INFO) && \
(tinfo->flags & TINFO_FLAG_NUWA_SUPPORT) && \
!(tinfo->flags & TINFO_FLAG_NUWA_EXPLICIT_CHECKPOINT)) { \
if (!setjmp(tinfo->jmpEnv)) { \
REAL(pthread_mutex_lock)(&sThreadCountLock); \
SaveTLSInfo(tinfo); \
sThreadFreezeCount++; \
freezeCountChg = true; \
pthread_cond_signal(&sThreadChangeCond); \
pthread_mutex_unlock(&sThreadCountLock); \
\
if (sIsFreezing) { \
REAL(pthread_mutex_lock)(&sThreadFreezeLock); \
/* Never return from the pthread_mutex_lock() call. */ \
abort(); \
} \
} else { \
RECREATE_CONTINUE(); \
RECREATE_GATE(); \
freezeCountChg = false; \
recreated = true; \
} \
}
#define THREAD_FREEZE_POINT1_VIP() \
bool freezeCountChg = false; \
bool recreated = false; \
volatile bool freezePoint1 = false; \
volatile bool freezePoint2 = false; \
thread_info_t *tinfo; \
if (sIsNuwaProcess && \
(tinfo = CUR_THREAD_INFO) && \
(tinfo->flags & TINFO_FLAG_NUWA_SUPPORT) && \
!(tinfo->flags & TINFO_FLAG_NUWA_EXPLICIT_CHECKPOINT)) { \
if (!setjmp(tinfo->jmpEnv)) { \
REAL(pthread_mutex_lock)(&sThreadCountLock); \
SaveTLSInfo(tinfo); \
sThreadFreezeCount++; \
sRecreateVIPCount++; \
freezeCountChg = true; \
pthread_cond_signal(&sThreadChangeCond); \
pthread_mutex_unlock(&sThreadCountLock); \
\
if (sIsFreezing) { \
freezePoint1 = true; \
REAL(pthread_mutex_lock)(&sThreadFreezeLock); \
/* Never return from the pthread_mutex_lock() call. */ \
abort(); \
} \
} else { \
freezeCountChg = false; \
recreated = true; \
} \
}
#define THREAD_FREEZE_POINT2() \
if (freezeCountChg) { \
REAL(pthread_mutex_lock)(&sThreadCountLock); \
if (sNuwaReady && sIsNuwaProcess) { \
pthread_mutex_unlock(&sThreadCountLock); \
freezePoint2 = true; \
REAL(pthread_mutex_lock)(&sThreadFreezeLock); \
/* Never return from the pthread_mutex_lock() call. */ \
abort(); \
} \
sThreadFreezeCount--; \
pthread_cond_signal(&sThreadChangeCond); \
pthread_mutex_unlock(&sThreadCountLock); \
}
#define THREAD_FREEZE_POINT2_VIP() \
if (freezeCountChg) { \
REAL(pthread_mutex_lock)(&sThreadCountLock); \
if (sNuwaReady && sIsNuwaProcess) { \
pthread_mutex_unlock(&sThreadCountLock); \
freezePoint2 = true; \
REAL(pthread_mutex_lock)(&sThreadFreezeLock); \
/* Never return from the pthread_mutex_lock() call. */ \
abort(); \
} \
sThreadFreezeCount--; \
sRecreateVIPCount--; \
pthread_cond_signal(&sThreadChangeCond); \
pthread_mutex_unlock(&sThreadCountLock); \
}
/**
* Wrapping the blocking functions: epoll_wait(), poll(), pthread_mutex_lock(),
* pthread_cond_wait() and pthread_cond_timedwait():
*
* These functions are wrapped by the above freeze point macros. Once a new
* process is forked, the recreated thread will be blocked in one of the wrapper
* functions. When recreating the thread, we longjmp() to
* THREAD_FREEZE_POINT1() to recover the thread stack. Care must be taken to
* maintain the semantics of the wrapped function:
*
* - epoll_wait() and poll(): just retry the function.
* - pthread_mutex_lock(): don't lock if frozen at freeze point 2 (lock is
* already acquired).
* - pthread_cond_wait() and pthread_cond_timedwait(): if the thread is frozen
* waiting the condition variable, the mutex is already released, we need to
* reacquire the mutex before calling the wrapped function again so the mutex
* will be in a valid state.
*/
extern "C" MFBT_API int
__wrap_epoll_wait(int epfd,
struct epoll_event *events,
int maxevents,
int timeout) {
int rv;
THREAD_FREEZE_POINT1();
rv = REAL(epoll_wait)(epfd, events, maxevents, timeout);
THREAD_FREEZE_POINT2();
return rv;
}
extern "C" MFBT_API int
__wrap_pthread_cond_wait(pthread_cond_t *cond,
pthread_mutex_t *mtx) {
int rv = 0;
THREAD_FREEZE_POINT1_VIP();
if (freezePoint2) {
RECREATE_CONTINUE();
RECREATE_PASS_VIP();
RECREATE_GATE_VIP();
return rv;
}
if (recreated && mtx) {
if (!freezePoint1) {
tinfo->condMutex = mtx;
// The thread was frozen in pthread_cond_wait() after releasing mtx in the
// Nuwa process. In recreating this thread, We failed to reacquire mtx
// with the pthread_mutex_trylock() call, that is, mtx was acquired by
// another thread. Because of this, we need the main thread's help to
// reacquire mtx so that it will be in a valid state.
if (!pthread_mutex_trylock(mtx)) {
tinfo->condMutexNeedsBalancing = true;
}
}
RECREATE_CONTINUE();
RECREATE_PASS_VIP();
}
rv = REAL(pthread_cond_wait)(cond, mtx);
if (recreated && mtx) {
// We have reacquired mtx. The main thread also wants to acquire mtx to
// synchronize with us. If the main thread didn't get a chance to acquire
// mtx let it do that now. The main thread clears condMutex after acquiring
// it to signal us.
if (tinfo->condMutex) {
// We need mtx to end up locked, so tell the main thread not to unlock
// mtx after it locks it.
tinfo->condMutexNeedsBalancing = false;
pthread_mutex_unlock(mtx);
}
// We still need to be gated as not to acquire another mutex associated with
// another VIP thread and interfere with it.
RECREATE_GATE_VIP();
}
THREAD_FREEZE_POINT2_VIP();
return rv;
}
extern "C" MFBT_API int
__wrap_pthread_cond_timedwait(pthread_cond_t *cond,
pthread_mutex_t *mtx,
const struct timespec *abstime) {
int rv = 0;
THREAD_FREEZE_POINT1_VIP();
if (freezePoint2) {
RECREATE_CONTINUE();
RECREATE_PASS_VIP();
RECREATE_GATE_VIP();
return rv;
}
if (recreated && mtx) {
if (!freezePoint1) {
tinfo->condMutex = mtx;
if (!pthread_mutex_trylock(mtx)) {
tinfo->condMutexNeedsBalancing = true;
}
}
RECREATE_CONTINUE();
RECREATE_PASS_VIP();
}
rv = REAL(pthread_cond_timedwait)(cond, mtx, abstime);
if (recreated && mtx) {
if (tinfo->condMutex) {
tinfo->condMutexNeedsBalancing = false;
pthread_mutex_unlock(mtx);
}
RECREATE_GATE_VIP();
}
THREAD_FREEZE_POINT2_VIP();
return rv;
}
extern "C" MFBT_API int
__wrap_pthread_mutex_lock(pthread_mutex_t *mtx) {
int rv = 0;
THREAD_FREEZE_POINT1();
if (freezePoint2) {
return rv;
}
rv = REAL(pthread_mutex_lock)(mtx);
THREAD_FREEZE_POINT2();
return rv;
}
extern "C" MFBT_API int
__wrap_poll(struct pollfd *fds, nfds_t nfds, int timeout) {
int rv;
THREAD_FREEZE_POINT1();
rv = REAL(poll)(fds, nfds, timeout);
THREAD_FREEZE_POINT2();
return rv;
}
extern "C" MFBT_API int
__wrap_epoll_create(int size) {
int epollfd = REAL(epoll_create)(size);
if (!sIsNuwaProcess) {
return epollfd;
}
if (epollfd >= 0) {
EpollManager::Singleton()->AddEpollInfo(epollfd, size);
}
return epollfd;
}
/**
* Wrapping the functions to create file descriptor pairs. In the child process
* FD pairs are created for intra-process signaling. The generation of FD pairs
* need to be tracked in the nuwa process so they can be recreated in the
* spawned process.
*/
struct FdPairInfo {
enum {
kPipe,
kSocketpair
} call;
int FDs[2];
int flags;
int domain;
int type;
int protocol;
};
/**
* Protects the access to sSingalFds.
*/
static pthread_mutex_t sSignalFdLock = PTHREAD_MUTEX_INITIALIZER;
static std::vector<FdPairInfo> sSignalFds;
extern "C" MFBT_API int
__wrap_socketpair(int domain, int type, int protocol, int sv[2])
{
int rv = REAL(socketpair)(domain, type, protocol, sv);
if (!sIsNuwaProcess || rv < 0) {
return rv;
}
REAL(pthread_mutex_lock)(&sSignalFdLock);
FdPairInfo signalFd;
signalFd.call = FdPairInfo::kSocketpair;
signalFd.FDs[0] = sv[0];
signalFd.FDs[1] = sv[1];
signalFd.domain = domain;
signalFd.type = type;
signalFd.protocol = protocol;
sSignalFds.push_back(signalFd);
pthread_mutex_unlock(&sSignalFdLock);
return rv;
}
extern "C" MFBT_API int
__wrap_pipe2(int __pipedes[2], int flags)
{
int rv = REAL(pipe2)(__pipedes, flags);
if (!sIsNuwaProcess || rv < 0) {
return rv;
}
REAL(pthread_mutex_lock)(&sSignalFdLock);
FdPairInfo signalFd;
signalFd.call = FdPairInfo::kPipe;
signalFd.FDs[0] = __pipedes[0];
signalFd.FDs[1] = __pipedes[1];
signalFd.flags = flags;
sSignalFds.push_back(signalFd);
pthread_mutex_unlock(&sSignalFdLock);
return rv;
}
extern "C" MFBT_API int
__wrap_pipe(int __pipedes[2])
{
return __wrap_pipe2(__pipedes, 0);
}
static void
DupeSingleFd(int newFd, int origFd)
{
struct stat sb;
if (fstat(origFd, &sb)) {
// Maybe the original FD is closed.
return;
}
int fd = fcntl(origFd, F_GETFD);
int fl = fcntl(origFd, F_GETFL);
dup2(newFd, origFd);
fcntl(origFd, F_SETFD, fd);
fcntl(origFd, F_SETFL, fl);
REAL(close)(newFd);
}
extern "C" MFBT_API void
ReplaceSignalFds()
{
for (std::vector<FdPairInfo>::iterator it = sSignalFds.begin();
it < sSignalFds.end(); ++it) {
int fds[2];
int rc = 0;
switch (it->call) {
case FdPairInfo::kPipe:
rc = REAL(pipe2)(fds, it->flags);
break;
case FdPairInfo::kSocketpair:
rc = REAL(socketpair)(it->domain, it->type, it->protocol, fds);
break;
default:
continue;
}
if (rc == 0) {
DupeSingleFd(fds[0], it->FDs[0]);
DupeSingleFd(fds[1], it->FDs[1]);
}
}
}
extern "C" MFBT_API int
__wrap_epoll_ctl(int aEpollFd, int aOp, int aFd, struct epoll_event *aEvent) {
int rv = REAL(epoll_ctl)(aEpollFd, aOp, aFd, aEvent);
if (!sIsNuwaProcess || rv == -1) {
return rv;
}
EpollManager::EpollInfo *info =
EpollManager::Singleton()->FindEpollInfo(aEpollFd);
if (info == nullptr) {
abort();
}
switch(aOp) {
case EPOLL_CTL_ADD:
info->AddEvents(aFd, *aEvent);
break;
case EPOLL_CTL_MOD:
info->ModifyEvents(aFd, *aEvent);
break;
case EPOLL_CTL_DEL:
info->RemoveEvents(aFd);
break;
default:
abort();
}
return rv;
}
// XXX: thinker: Maybe, we should also track dup, dup2, and other functions.
extern "C" MFBT_API int
__wrap_close(int aFd) {
int rv = REAL(close)(aFd);
if (!sIsNuwaProcess || rv == -1) {
return rv;
}
EpollManager::EpollInfo *info =
EpollManager::Singleton()->FindEpollInfo(aFd);
if (info) {
EpollManager::Singleton()->RemoveEpollInfo(aFd);
}
return rv;
}
static void *
thread_recreate_startup(void *arg) {
/*
* Dark Art!! Never do the same unless you are ABSOLUTELY sure what you are
* doing!
*
* The stack space collapsed by this frame had been reserved by
* thread_create_startup(). And thread_create_startup() will
* return immediately after returning from real start routine, so
* all collapsed values does not affect the result.
*
* All outer frames of thread_create_startup() and
* thread_recreate_startup() are equivalent, so
* thread_create_startup() will return successfully.
*/
thread_info_t *tinfo = (thread_info_t *)arg;
prctl(PR_SET_NAME, (unsigned long)&tinfo->nativeThreadName, 0, 0, 0);
RestoreTLSInfo(tinfo);
if (setjmp(tinfo->retEnv) != 0) {
return nullptr;
}
// longjump() to recreate the stack on the new thread.
longjmp(tinfo->jmpEnv, 1);
// Never go here!
abort();
return nullptr;
}
/**
* Recreate the context given by tinfo at a new thread.
*/
static void
thread_recreate(thread_info_t *tinfo) {
pthread_t thread;
// Note that the thread_recreate_startup() runs on the stack specified by
// tinfo.
pthread_create(&thread, &tinfo->threadAttr, thread_recreate_startup, tinfo);
}
/**
* Recreate all threads in a process forked from an Nuwa process.
*/
static void
RecreateThreads() {
sIsNuwaProcess = false;
sIsFreezing = false;
sMainThread.recreatedThreadID = pthread_self();
sMainThread.recreatedNativeThreadID = gettid();
// Run registered constructors.
for (std::vector<nuwa_construct_t>::iterator ctr = sConstructors.begin();
ctr != sConstructors.end();
ctr++) {
(*ctr).construct((*ctr).arg);
}
sConstructors.clear();
REAL(pthread_mutex_lock)(&sThreadCountLock);
thread_info_t *tinfo = sAllThreads.getFirst();
pthread_mutex_unlock(&sThreadCountLock);
RECREATE_START();
while (tinfo != nullptr) {
if (tinfo->flags & TINFO_FLAG_NUWA_SUPPORT) {
RECREATE_BEFORE(tinfo);
thread_recreate(tinfo);
RECREATE_WAIT();
if (tinfo->condMutex) {
// Synchronize with the recreated thread in pthread_cond_wait().
REAL(pthread_mutex_lock)(tinfo->condMutex);
// Tell the other thread that we have successfully locked the mutex.
// NB: condMutex can only be touched while it is held, so we must clear
// it here and store the mutex locally.
pthread_mutex_t *mtx = tinfo->condMutex;
tinfo->condMutex = nullptr;
if (tinfo->condMutexNeedsBalancing) {
pthread_mutex_unlock(mtx);
}
}
} else if(!(tinfo->flags & TINFO_FLAG_NUWA_SKIP)) {
// An unmarked thread is found other than the main thread.
// All threads should be marked as one of SUPPORT or SKIP, or
// abort the process to make sure all threads in the Nuwa
// process are Nuwa-aware.
abort();
}
tinfo = tinfo->getNext();
}
RECREATE_WAIT_ALL_VIP();
RECREATE_OPEN_GATE();
RECREATE_FINISH();
// Run registered final constructors.
for (std::vector<nuwa_construct_t>::iterator ctr = sFinalConstructors.begin();
ctr != sFinalConstructors.end();
ctr++) {
(*ctr).construct((*ctr).arg);
}
sFinalConstructors.clear();
}
extern "C" {
/**
* Recreate all epoll fds and restore status; include all events.
*/
static void
RecreateEpollFds() {
EpollManager *man = EpollManager::Singleton();
for (EpollManager::const_iterator info_it = man->begin();
info_it != man->end();
info_it++) {
int epollfd = info_it->first;
const EpollManager::EpollInfo *info = &info_it->second;
int fdflags = fcntl(epollfd, F_GETFD);
if (fdflags == -1) {
abort();
}
int fl = fcntl(epollfd, F_GETFL);
if (fl == -1) {
abort();
}
int newepollfd = REAL(epoll_create)(info->BackSize());
if (newepollfd == -1) {
abort();
}
int rv = REAL(close)(epollfd);
if (rv == -1) {
abort();
}
rv = dup2(newepollfd, epollfd);
if (rv == -1) {
abort();
}
rv = REAL(close)(newepollfd);
if (rv == -1) {
abort();
}
rv = fcntl(epollfd, F_SETFD, fdflags);
if (rv == -1) {
abort();
}
rv = fcntl(epollfd, F_SETFL, fl);
if (rv == -1) {
abort();
}
for (EpollManager::EpollInfo::const_iterator events_it = info->begin();
events_it != info->end();
events_it++) {
int fd = events_it->first;
epoll_event events;
events = events_it->second;
rv = REAL(epoll_ctl)(epollfd, EPOLL_CTL_ADD, fd, &events);
if (rv == -1) {
abort();
}
}
}
// Shutdown EpollManager. It won't be needed in the spawned process.
EpollManager::Shutdown();
}
/**
* Fix IPC to make it ready.
*
* Especially, fix ContentChild.
*/
static void
ReplaceIPC(NuwaProtoFdInfo *aInfoList, int aInfoSize) {
int i;
int rv;
for (i = 0; i < aInfoSize; i++) {
int fd = fcntl(aInfoList[i].originFd, F_GETFD);
if (fd == -1) {
abort();
}
int fl = fcntl(aInfoList[i].originFd, F_GETFL);
if (fl == -1) {
abort();
}
rv = dup2(aInfoList[i].newFds[NUWA_NEWFD_CHILD], aInfoList[i].originFd);
if (rv == -1) {
abort();
}
rv = fcntl(aInfoList[i].originFd, F_SETFD, fd);
if (rv == -1) {
abort();
}
rv = fcntl(aInfoList[i].originFd, F_SETFL, fl);
if (rv == -1) {
abort();
}
}
}
/**
* Add a new content process at the chrome process.
*/
static void
AddNewProcess(pid_t pid, NuwaProtoFdInfo *aInfoList, int aInfoSize) {
static bool (*AddNewIPCProcess)(pid_t, NuwaProtoFdInfo *, int) = nullptr;
if (AddNewIPCProcess == nullptr) {
AddNewIPCProcess = (bool (*)(pid_t, NuwaProtoFdInfo *, int))
dlsym(RTLD_DEFAULT, "AddNewIPCProcess");
}
AddNewIPCProcess(pid, aInfoList, aInfoSize);
}
static void
PrepareProtoSockets(NuwaProtoFdInfo *aInfoList, int aInfoSize) {
int i;
int rv;
for (i = 0; i < aInfoSize; i++) {
rv = REAL(socketpair)(PF_UNIX, SOCK_STREAM, 0, aInfoList[i].newFds);
if (rv == -1) {
abort();
}
}
}
static void
CloseAllProtoSockets(NuwaProtoFdInfo *aInfoList, int aInfoSize) {
int i;
for (i = 0; i < aInfoSize; i++) {
REAL(close)(aInfoList[i].newFds[0]);
REAL(close)(aInfoList[i].newFds[1]);
}
}
static void
AfterForkHook()
{
void (*AfterNuwaFork)();
// This is defined in dom/ipc/ContentChild.cpp
AfterNuwaFork = (void (*)())
dlsym(RTLD_DEFAULT, "AfterNuwaFork");
AfterNuwaFork();
}
/**
* Fork a new process that is ready for running IPC.
*
* @return the PID of the new process.
*/
static int
ForkIPCProcess() {
int pid;
REAL(pthread_mutex_lock)(&sForkLock);
PrepareProtoSockets(sProtoFdInfos, sProtoFdInfosSize);
sNuwaForking = true;
pid = fork();
sNuwaForking = false;
if (pid == -1) {
abort();
}
if (pid > 0) {
// in the parent
AddNewProcess(pid, sProtoFdInfos, sProtoFdInfosSize);
CloseAllProtoSockets(sProtoFdInfos, sProtoFdInfosSize);
} else {
// in the child
if (getenv("MOZ_DEBUG_CHILD_PROCESS")) {
printf("\n\nNUWA CHILDCHILDCHILDCHILD\n debug me @ %d\n\n", getpid());
sleep(30);
}
AfterForkHook();
ReplaceSignalFds();
ReplaceIPC(sProtoFdInfos, sProtoFdInfosSize);
RecreateEpollFds();
RecreateThreads();
CloseAllProtoSockets(sProtoFdInfos, sProtoFdInfosSize);
}
sForkWaitCondChanged = true;
pthread_cond_signal(&sForkWaitCond);
pthread_mutex_unlock(&sForkLock);
return pid;
}
/**
* Prepare for spawning a new process. Called on the IPC thread.
*/
MFBT_API void
NuwaSpawnPrepare() {
REAL(pthread_mutex_lock)(&sForkLock);
sForkWaitCondChanged = false; // Will be modified on the main thread.
}
/**
* Let IPC thread wait until fork action on the main thread has completed.
*/
MFBT_API void
NuwaSpawnWait() {
while (!sForkWaitCondChanged) {
REAL(pthread_cond_wait)(&sForkWaitCond, &sForkLock);
}
pthread_mutex_unlock(&sForkLock);
}
/**
* Spawn a new process. If not ready for spawn (still waiting for some threads
* to freeze), postpone the spawn request until ready.
*
* @return the pid of the new process, or 0 if not ready.
*/
MFBT_API pid_t
NuwaSpawn() {
if (gettid() != getpid()) {
// Not the main thread.
abort();
}
pid_t pid = 0;
if (sNuwaReady) {
pid = ForkIPCProcess();
} else {
sNuwaPendingSpawn = true;
}
return pid;
}
/**
* Prepare to freeze the Nuwa-supporting threads.
*/
MFBT_API void
PrepareNuwaProcess() {
sIsNuwaProcess = true;
// Explicitly ignore SIGCHLD so we don't have to call watpid() to reap
// dead child processes.
signal(SIGCHLD, SIG_IGN);
// Make marked threads block in one freeze point.
REAL(pthread_mutex_lock)(&sThreadFreezeLock);
// Populate sMainThread for mapping of tgkill.
sMainThread.origThreadID = pthread_self();
sMainThread.origNativeThreadID = gettid();
}
// Make current process as a Nuwa process.
MFBT_API void
MakeNuwaProcess() {
void (*GetProtoFdInfos)(NuwaProtoFdInfo *, int, int *) = nullptr;
void (*OnNuwaProcessReady)() = nullptr;
sIsFreezing = true;
REAL(pthread_mutex_lock)(&sThreadCountLock);
// wait until all threads are frozen.
while ((sThreadFreezeCount + sThreadSkipCount) != sThreadCount) {
REAL(pthread_cond_wait)(&sThreadChangeCond, &sThreadCountLock);
}
GetProtoFdInfos = (void (*)(NuwaProtoFdInfo *, int, int *))
dlsym(RTLD_DEFAULT, "GetProtoFdInfos");
GetProtoFdInfos(sProtoFdInfos, NUWA_TOPLEVEL_MAX, &sProtoFdInfosSize);
sNuwaReady = true;
pthread_mutex_unlock(&sThreadCountLock);
OnNuwaProcessReady = (void (*)())dlsym(RTLD_DEFAULT, "OnNuwaProcessReady");
OnNuwaProcessReady();
if (sNuwaPendingSpawn) {
sNuwaPendingSpawn = false;
NuwaSpawn();
}
}
/**
* Mark the current thread as supporting Nuwa. The thread will be recreated in
* the spawned process.
*/
MFBT_API void
NuwaMarkCurrentThread(void (*recreate)(void *), void *arg) {
if (!sIsNuwaProcess) {
return;
}
thread_info_t *tinfo = CUR_THREAD_INFO;
if (tinfo == nullptr) {
abort();
}
tinfo->flags |= TINFO_FLAG_NUWA_SUPPORT;
if (recreate) {
nuwa_construct_t construct(recreate, arg);
tinfo->addThreadConstructor(&construct);
}
// XXX Thread name might be set later than this call. If this is the case, we
// might need to delay getting the thread name.
prctl(PR_GET_NAME, (unsigned long)&tinfo->nativeThreadName, 0, 0, 0);
}
/**
* Mark the current thread as not supporting Nuwa. Don't recreate this thread in
* the spawned process.
*/
MFBT_API void
NuwaSkipCurrentThread() {
if (!sIsNuwaProcess) return;
thread_info_t *tinfo = CUR_THREAD_INFO;
if (tinfo == nullptr) {
abort();
}
if (!(tinfo->flags & TINFO_FLAG_NUWA_SKIP)) {
sThreadSkipCount++;
}
tinfo->flags |= TINFO_FLAG_NUWA_SKIP;
}
/**
* Force to freeze the current thread.
*
* This method does not return in Nuwa process. It returns for the
* recreated thread.
*/
MFBT_API void
NuwaFreezeCurrentThread() {
thread_info_t *tinfo = CUR_THREAD_INFO;
if (sIsNuwaProcess &&
(tinfo = CUR_THREAD_INFO) &&
(tinfo->flags & TINFO_FLAG_NUWA_SUPPORT)) {
if (!setjmp(tinfo->jmpEnv)) {
REAL(pthread_mutex_lock)(&sThreadCountLock);
SaveTLSInfo(tinfo);
sThreadFreezeCount++;
pthread_cond_signal(&sThreadChangeCond);
pthread_mutex_unlock(&sThreadCountLock);
REAL(pthread_mutex_lock)(&sThreadFreezeLock);
} else {
RECREATE_CONTINUE();
RECREATE_GATE();
}
}
}
/**
* The caller of NuwaCheckpointCurrentThread() is at the line it wishes to
* return after the thread is recreated.
*
* The checkpointed thread will restart at the calling line of
* NuwaCheckpointCurrentThread(). This macro returns true in the Nuwa process
* and false on the recreated thread in the forked process.
*
* NuwaCheckpointCurrentThread() is implemented as a macro so we can place the
* setjmp() call in the calling method without changing its stack pointer. This
* is essential for not corrupting the stack when the calling thread continues
* to request the main thread for forking a new process. The caller of
* NuwaCheckpointCurrentThread() should not return before the process forking
* finishes.
*
* @return true for Nuwa process, and false in the forked process.
*/
MFBT_API jmp_buf*
NuwaCheckpointCurrentThread1() {
thread_info_t *tinfo = CUR_THREAD_INFO;
if (sIsNuwaProcess &&
(tinfo = CUR_THREAD_INFO) &&
(tinfo->flags & TINFO_FLAG_NUWA_SUPPORT)) {
return &tinfo->jmpEnv;
}
abort();
return nullptr;
}
MFBT_API bool
NuwaCheckpointCurrentThread2(int setjmpCond) {
thread_info_t *tinfo = CUR_THREAD_INFO;
if (setjmpCond == 0) {
REAL(pthread_mutex_lock)(&sThreadCountLock);
if (!(tinfo->flags & TINFO_FLAG_NUWA_EXPLICIT_CHECKPOINT)) {
tinfo->flags |= TINFO_FLAG_NUWA_EXPLICIT_CHECKPOINT;
SaveTLSInfo(tinfo);
sThreadFreezeCount++;
}
pthread_cond_signal(&sThreadChangeCond);
pthread_mutex_unlock(&sThreadCountLock);
return true;
}
RECREATE_CONTINUE();
RECREATE_GATE();
return false; // Recreated thread.
}
/**
* Register methods to be invoked before recreating threads in the spawned
* process.
*/
MFBT_API void
NuwaAddConstructor(void (*construct)(void *), void *arg) {
nuwa_construct_t ctr(construct, arg);
sConstructors.push_back(ctr);
}
/**
* Register methods to be invoked after recreating threads in the spawned
* process.
*/
MFBT_API void
NuwaAddFinalConstructor(void (*construct)(void *), void *arg) {
nuwa_construct_t ctr(construct, arg);
sFinalConstructors.push_back(ctr);
}
MFBT_API void
NuwaAddThreadConstructor(void (*aConstruct)(void *), void *aArg) {
thread_info *tinfo = CUR_THREAD_INFO;
if (!tinfo || !aConstruct) {
return;
}
nuwa_construct_t construct(aConstruct, aArg);
tinfo->addThreadConstructor(&construct);
}
/**
* @return if the current process is the nuwa process.
*/
MFBT_API bool
IsNuwaProcess() {
return sIsNuwaProcess;
}
/**
* @return if the nuwa process is ready for spawning new processes.
*/
MFBT_API bool
IsNuwaReady() {
return sNuwaReady;
}
} // extern "C"
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