pthread_create.cpp revision cef3faec0ea40fdfe58e425fd0be64f00de6a26d
1/* 2 * Copyright (C) 2008 The Android Open Source Project 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * * Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * * Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in 12 * the documentation and/or other materials provided with the 13 * distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS 22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29#include <pthread.h> 30 31#include <errno.h> 32#include <sys/mman.h> 33 34#include "pthread_internal.h" 35 36#include "private/bionic_ssp.h" 37#include "private/bionic_tls.h" 38#include "private/libc_logging.h" 39#include "private/thread_private.h" 40#include "private/ErrnoRestorer.h" 41#include "private/ScopedPthreadMutexLocker.h" 42 43extern "C" pid_t __bionic_clone(uint32_t flags, void* child_stack, int* parent_tid, void* tls, int* child_tid, int (*fn)(void*), void* arg); 44 45#ifdef __i386__ 46#define ATTRIBUTES __attribute__((noinline)) __attribute__((fastcall)) 47#else 48#define ATTRIBUTES __attribute__((noinline)) 49#endif 50 51extern "C" void ATTRIBUTES _thread_created_hook(pid_t thread_id); 52 53static pthread_mutex_t gPthreadStackCreationLock = PTHREAD_MUTEX_INITIALIZER; 54 55static pthread_mutex_t gDebuggerNotificationLock = PTHREAD_MUTEX_INITIALIZER; 56 57// This code is used both by each new pthread and the code that initializes the main thread. 58void __init_tls(pthread_internal_t* thread) { 59 // Zero-initialize all the slots after TLS_SLOT_SELF and TLS_SLOT_THREAD_ID. 60 for (size_t i = TLS_SLOT_ERRNO; i < BIONIC_TLS_SLOTS; ++i) { 61 thread->tls[i] = NULL; 62 } 63 64 // Slot 0 must point to itself. The x86 Linux kernel reads the TLS from %fs:0. 65 thread->tls[TLS_SLOT_SELF] = thread->tls; 66 thread->tls[TLS_SLOT_THREAD_ID] = thread; 67 // GCC looks in the TLS for the stack guard on x86, so copy it there from our global. 68 thread->tls[TLS_SLOT_STACK_GUARD] = (void*) __stack_chk_guard; 69} 70 71void __init_alternate_signal_stack(pthread_internal_t* thread) { 72 // Create and set an alternate signal stack. 73 stack_t ss; 74 ss.ss_sp = mmap(NULL, SIGSTKSZ, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, 0, 0); 75 if (ss.ss_sp != MAP_FAILED) { 76 ss.ss_size = SIGSTKSZ; 77 ss.ss_flags = 0; 78 sigaltstack(&ss, NULL); 79 thread->alternate_signal_stack = ss.ss_sp; 80 } 81} 82 83int __init_thread(pthread_internal_t* thread, bool add_to_thread_list) { 84 int error = 0; 85 86 // Set the scheduling policy/priority of the thread. 87 if (thread->attr.sched_policy != SCHED_NORMAL) { 88 sched_param param; 89 param.sched_priority = thread->attr.sched_priority; 90 if (sched_setscheduler(thread->tid, thread->attr.sched_policy, ¶m) == -1) { 91#if __LP64__ 92 // For backwards compatibility reasons, we only report failures on 64-bit devices. 93 error = errno; 94#endif 95 __libc_format_log(ANDROID_LOG_WARN, "libc", 96 "pthread_create sched_setscheduler call failed: %s", strerror(errno)); 97 } 98 } 99 100 thread->cleanup_stack = NULL; 101 102 if (add_to_thread_list) { 103 _pthread_internal_add(thread); 104 } 105 106 return error; 107} 108 109static void* __create_thread_stack(pthread_internal_t* thread) { 110 ScopedPthreadMutexLocker lock(&gPthreadStackCreationLock); 111 112 // Create a new private anonymous map. 113 int prot = PROT_READ | PROT_WRITE; 114 int flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE; 115 void* stack = mmap(NULL, thread->attr.stack_size, prot, flags, -1, 0); 116 if (stack == MAP_FAILED) { 117 __libc_format_log(ANDROID_LOG_WARN, 118 "libc", 119 "pthread_create failed: couldn't allocate %zd-byte stack: %s", 120 thread->attr.stack_size, strerror(errno)); 121 return NULL; 122 } 123 124 // Set the guard region at the end of the stack to PROT_NONE. 125 if (mprotect(stack, thread->attr.guard_size, PROT_NONE) == -1) { 126 __libc_format_log(ANDROID_LOG_WARN, "libc", 127 "pthread_create failed: couldn't mprotect PROT_NONE %zd-byte stack guard region: %s", 128 thread->attr.guard_size, strerror(errno)); 129 munmap(stack, thread->attr.stack_size); 130 return NULL; 131 } 132 133 return stack; 134} 135 136static int __pthread_start(void* arg) { 137 pthread_internal_t* thread = reinterpret_cast<pthread_internal_t*>(arg); 138 139 // Wait for our creating thread to release us. This lets it have time to 140 // notify gdb about this thread before we start doing anything. 141 // This also provides the memory barrier needed to ensure that all memory 142 // accesses previously made by the creating thread are visible to us. 143 pthread_mutex_t* start_mutex = (pthread_mutex_t*) &thread->tls[TLS_SLOT_START_MUTEX]; 144 pthread_mutex_lock(start_mutex); 145 pthread_mutex_destroy(start_mutex); 146 147 __init_tls(thread); 148 149 __init_alternate_signal_stack(thread); 150 151 void* result = thread->start_routine(thread->start_routine_arg); 152 pthread_exit(result); 153 154 return 0; 155} 156 157// A dummy start routine for pthread_create failures where we've created a thread but aren't 158// going to run user code on it. We swap out the user's start routine for this and take advantage 159// of the regular thread teardown to free up resources. 160static void* __do_nothing(void*) { 161 return NULL; 162} 163 164int pthread_create(pthread_t* thread_out, pthread_attr_t const* attr, 165 void* (*start_routine)(void*), void* arg) { 166 ErrnoRestorer errno_restorer; 167 168 // Inform the rest of the C library that at least one thread 169 // was created. This will enforce certain functions to acquire/release 170 // locks (e.g. atexit()) to protect shared global structures. 171 // This works because pthread_create() is not called by the C library 172 // initialization routine that sets up the main thread's data structures. 173 __isthreaded = 1; 174 175 pthread_internal_t* thread = reinterpret_cast<pthread_internal_t*>(calloc(sizeof(*thread), 1)); 176 if (thread == NULL) { 177 __libc_format_log(ANDROID_LOG_WARN, "libc", "pthread_create failed: couldn't allocate thread"); 178 return EAGAIN; 179 } 180 181 if (attr == NULL) { 182 pthread_attr_init(&thread->attr); 183 } else { 184 thread->attr = *attr; 185 attr = NULL; // Prevent misuse below. 186 } 187 188 // Make sure the stack size and guard size are multiples of PAGE_SIZE. 189 thread->attr.stack_size = (thread->attr.stack_size + (PAGE_SIZE-1)) & ~(PAGE_SIZE-1); 190 thread->attr.guard_size = (thread->attr.guard_size + (PAGE_SIZE-1)) & ~(PAGE_SIZE-1); 191 192 if (thread->attr.stack_base == NULL) { 193 // The caller didn't provide a stack, so allocate one. 194 thread->attr.stack_base = __create_thread_stack(thread); 195 if (thread->attr.stack_base == NULL) { 196 free(thread); 197 return EAGAIN; 198 } 199 } else { 200 // The caller did provide a stack, so remember we're not supposed to free it. 201 thread->attr.flags |= PTHREAD_ATTR_FLAG_USER_ALLOCATED_STACK; 202 } 203 204 // Make room for the TLS area. 205 // The child stack is the same address, just growing in the opposite direction. 206 // At offsets >= 0, we have the TLS slots. 207 // At offsets < 0, we have the child stack. 208 thread->tls = (void**)((uint8_t*)(thread->attr.stack_base) + thread->attr.stack_size - BIONIC_TLS_SLOTS * sizeof(void*)); 209 void* child_stack = thread->tls; 210 211 // Create a mutex for the thread in TLS to wait on once it starts so we can keep 212 // it from doing anything until after we notify the debugger about it 213 // 214 // This also provides the memory barrier we need to ensure that all 215 // memory accesses previously performed by this thread are visible to 216 // the new thread. 217 pthread_mutex_t* start_mutex = (pthread_mutex_t*) &thread->tls[TLS_SLOT_START_MUTEX]; 218 pthread_mutex_init(start_mutex, NULL); 219 pthread_mutex_lock(start_mutex); 220 221 thread->tls[TLS_SLOT_THREAD_ID] = thread; 222 223 thread->start_routine = start_routine; 224 thread->start_routine_arg = arg; 225 226 int flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM | 227 CLONE_SETTLS | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID; 228 int rc = __bionic_clone(flags, child_stack, &(thread->tid), thread->tls, &(thread->tid), __pthread_start, thread); 229 if (rc == -1) { 230 int clone_errno = errno; 231 // We don't have to unlock the mutex at all because clone(2) failed so there's no child waiting to 232 // be unblocked, but we're about to unmap the memory the mutex is stored in, so this serves as a 233 // reminder that you can't rewrite this function to use a ScopedPthreadMutexLocker. 234 pthread_mutex_unlock(start_mutex); 235 if ((thread->attr.flags & PTHREAD_ATTR_FLAG_USER_ALLOCATED_STACK) == 0) { 236 munmap(thread->attr.stack_base, thread->attr.stack_size); 237 } 238 free(thread); 239 __libc_format_log(ANDROID_LOG_WARN, "libc", "pthread_create failed: clone failed: %s", strerror(errno)); 240 return clone_errno; 241 } 242 243 int init_errno = __init_thread(thread, true); 244 if (init_errno != 0) { 245 // Mark the thread detached and replace its start_routine with a no-op. 246 // Letting the thread run is the easiest way to clean up its resources. 247 thread->attr.flags |= PTHREAD_ATTR_FLAG_DETACHED; 248 thread->start_routine = __do_nothing; 249 pthread_mutex_unlock(start_mutex); 250 return init_errno; 251 } 252 253 // Notify any debuggers about the new thread. 254 { 255 ScopedPthreadMutexLocker debugger_locker(&gDebuggerNotificationLock); 256 _thread_created_hook(thread->tid); 257 } 258 259 // Publish the pthread_t and unlock the mutex to let the new thread start running. 260 *thread_out = reinterpret_cast<pthread_t>(thread); 261 pthread_mutex_unlock(start_mutex); 262 263 return 0; 264} 265