pthread_create.cpp revision e48b68570d872ef7ece1d873c0ea298ea76393f3
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 pthread_cond_init(&thread->join_cond, NULL); 101 thread->cleanup_stack = NULL; 102 103 if (add_to_thread_list) { 104 _pthread_internal_add(thread); 105 } 106 107 return error; 108} 109 110static void* __create_thread_stack(pthread_internal_t* thread) { 111 ScopedPthreadMutexLocker lock(&gPthreadStackCreationLock); 112 113 // Create a new private anonymous map. 114 int prot = PROT_READ | PROT_WRITE; 115 int flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE; 116 void* stack = mmap(NULL, thread->attr.stack_size, prot, flags, -1, 0); 117 if (stack == MAP_FAILED) { 118 __libc_format_log(ANDROID_LOG_WARN, 119 "libc", 120 "pthread_create failed: couldn't allocate %zd-byte stack: %s", 121 thread->attr.stack_size, strerror(errno)); 122 return NULL; 123 } 124 125 // Set the guard region at the end of the stack to PROT_NONE. 126 if (mprotect(stack, thread->attr.guard_size, PROT_NONE) == -1) { 127 __libc_format_log(ANDROID_LOG_WARN, "libc", 128 "pthread_create failed: couldn't mprotect PROT_NONE %zd-byte stack guard region: %s", 129 thread->attr.guard_size, strerror(errno)); 130 munmap(stack, thread->attr.stack_size); 131 return NULL; 132 } 133 134 return stack; 135} 136 137static int __pthread_start(void* arg) { 138 pthread_internal_t* thread = reinterpret_cast<pthread_internal_t*>(arg); 139 140 // Wait for our creating thread to release us. This lets it have time to 141 // notify gdb about this thread before we start doing anything. 142 // This also provides the memory barrier needed to ensure that all memory 143 // accesses previously made by the creating thread are visible to us. 144 pthread_mutex_t* start_mutex = (pthread_mutex_t*) &thread->tls[TLS_SLOT_START_MUTEX]; 145 pthread_mutex_lock(start_mutex); 146 pthread_mutex_destroy(start_mutex); 147 148 __init_tls(thread); 149 150 __init_alternate_signal_stack(thread); 151 152 if ((thread->internal_flags & PTHREAD_INTERNAL_FLAG_THREAD_INIT_FAILED) != 0) { 153 pthread_exit(NULL); 154 } 155 156 void* result = thread->start_routine(thread->start_routine_arg); 157 pthread_exit(result); 158 159 return 0; 160} 161 162int pthread_create(pthread_t* thread_out, pthread_attr_t const* attr, 163 void* (*start_routine)(void*), void* arg) { 164 ErrnoRestorer errno_restorer; 165 166 // Inform the rest of the C library that at least one thread 167 // was created. This will enforce certain functions to acquire/release 168 // locks (e.g. atexit()) to protect shared global structures. 169 // This works because pthread_create() is not called by the C library 170 // initialization routine that sets up the main thread's data structures. 171 __isthreaded = 1; 172 173 pthread_internal_t* thread = reinterpret_cast<pthread_internal_t*>(calloc(sizeof(*thread), 1)); 174 if (thread == NULL) { 175 __libc_format_log(ANDROID_LOG_WARN, "libc", "pthread_create failed: couldn't allocate thread"); 176 return EAGAIN; 177 } 178 thread->allocated_on_heap = true; 179 180 if (attr == NULL) { 181 pthread_attr_init(&thread->attr); 182 } else { 183 thread->attr = *attr; 184 attr = NULL; // Prevent misuse below. 185 } 186 187 // Make sure the stack size and guard size are multiples of PAGE_SIZE. 188 thread->attr.stack_size = (thread->attr.stack_size + (PAGE_SIZE-1)) & ~(PAGE_SIZE-1); 189 thread->attr.guard_size = (thread->attr.guard_size + (PAGE_SIZE-1)) & ~(PAGE_SIZE-1); 190 191 if (thread->attr.stack_base == NULL) { 192 // The caller didn't provide a stack, so allocate one. 193 thread->attr.stack_base = __create_thread_stack(thread); 194 if (thread->attr.stack_base == NULL) { 195 free(thread); 196 return EAGAIN; 197 } 198 } else { 199 // The caller did provide a stack, so remember we're not supposed to free it. 200 thread->attr.flags |= PTHREAD_ATTR_FLAG_USER_ALLOCATED_STACK; 201 } 202 203 // Make room for the TLS area. 204 // The child stack is the same address, just growing in the opposite direction. 205 // At offsets >= 0, we have the TLS slots. 206 // At offsets < 0, we have the child stack. 207 thread->tls = (void**)((uint8_t*)(thread->attr.stack_base) + thread->attr.stack_size - BIONIC_TLS_SLOTS * sizeof(void*)); 208 void* child_stack = thread->tls; 209 210 // Create a mutex for the thread in TLS to wait on once it starts so we can keep 211 // it from doing anything until after we notify the debugger about it 212 // 213 // This also provides the memory barrier we need to ensure that all 214 // memory accesses previously performed by this thread are visible to 215 // the new thread. 216 pthread_mutex_t* start_mutex = (pthread_mutex_t*) &thread->tls[TLS_SLOT_START_MUTEX]; 217 pthread_mutex_init(start_mutex, NULL); 218 ScopedPthreadMutexLocker start_locker(start_mutex); 219 220 thread->tls[TLS_SLOT_THREAD_ID] = thread; 221 222 thread->start_routine = start_routine; 223 thread->start_routine_arg = arg; 224 225 int flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM | CLONE_SETTLS; 226 int tid = __bionic_clone(flags, child_stack, NULL, thread->tls, NULL, __pthread_start, thread); 227 if (tid < 0) { 228 int clone_errno = errno; 229 if ((thread->attr.flags & PTHREAD_ATTR_FLAG_USER_ALLOCATED_STACK) == 0) { 230 munmap(thread->attr.stack_base, thread->attr.stack_size); 231 } 232 free(thread); 233 __libc_format_log(ANDROID_LOG_WARN, "libc", "pthread_create failed: clone failed: %s", strerror(errno)); 234 return clone_errno; 235 } 236 237 thread->tid = tid; 238 239 int init_errno = _init_thread(thread, true); 240 if (init_errno != 0) { 241 // Mark the thread detached and let its __pthread_start run to 242 // completion. (It'll just exit immediately, cleaning up its resources.) 243 thread->internal_flags |= PTHREAD_INTERNAL_FLAG_THREAD_INIT_FAILED; 244 thread->attr.flags |= PTHREAD_ATTR_FLAG_DETACHED; 245 return init_errno; 246 } 247 248 // Notify any debuggers about the new thread. 249 { 250 ScopedPthreadMutexLocker debugger_locker(&gDebuggerNotificationLock); 251 _thread_created_hook(thread->tid); 252 } 253 254 // Publish the pthread_t and let the thread run. 255 *thread_out = (pthread_t) thread; 256 257 return 0; 258} 259