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 43 extern "C" int __pthread_clone(void* (*fn)(void*), void* child_stack, int flags, void* arg); 44 45 #ifdef __i386__ 46 #define ATTRIBUTES __attribute__((noinline)) __attribute__((fastcall)) 47 #else 48 #define ATTRIBUTES __attribute__((noinline)) 49 #endif 50 51 extern "C" void ATTRIBUTES _thread_created_hook(pid_t thread_id); 52 53 static const int kPthreadInitFailed = 1; 54 55 static pthread_mutex_t gPthreadStackCreationLock = PTHREAD_MUTEX_INITIALIZER; 56 57 static pthread_mutex_t gDebuggerNotificationLock = PTHREAD_MUTEX_INITIALIZER; 58 59 void __init_tls(pthread_internal_t* thread) { 60 // Zero-initialize all the slots. 61 for (size_t i = 0; i < BIONIC_TLS_SLOTS; ++i) { 62 thread->tls[i] = NULL; 63 } 64 65 // Slot 0 must point to itself. The x86 Linux kernel reads the TLS from %fs:0. 66 thread->tls[TLS_SLOT_SELF] = thread->tls; 67 thread->tls[TLS_SLOT_THREAD_ID] = thread; 68 // GCC looks in the TLS for the stack guard on x86, so copy it there from our global. 69 thread->tls[TLS_SLOT_STACK_GUARD] = (void*) __stack_chk_guard; 70 71 __set_tls(thread->tls); 72 73 // Create and set an alternate signal stack. 74 // This must happen after __set_tls, in case a system call fails and tries to set errno. 75 stack_t ss; 76 ss.ss_sp = mmap(NULL, SIGSTKSZ, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, 0, 0); 77 if (ss.ss_sp != MAP_FAILED) { 78 ss.ss_size = SIGSTKSZ; 79 ss.ss_flags = 0; 80 sigaltstack(&ss, NULL); 81 thread->alternate_signal_stack = ss.ss_sp; 82 } 83 } 84 85 // This trampoline is called from the assembly _pthread_clone function. 86 // Our 'tls' and __pthread_clone's 'child_stack' are one and the same, just growing in 87 // opposite directions. 88 extern "C" void __thread_entry(void* (*func)(void*), void* arg, void** tls) { 89 // Wait for our creating thread to release us. This lets it have time to 90 // notify gdb about this thread before we start doing anything. 91 // This also provides the memory barrier needed to ensure that all memory 92 // accesses previously made by the creating thread are visible to us. 93 pthread_mutex_t* start_mutex = (pthread_mutex_t*) &tls[TLS_SLOT_SELF]; 94 pthread_mutex_lock(start_mutex); 95 pthread_mutex_destroy(start_mutex); 96 97 pthread_internal_t* thread = (pthread_internal_t*) tls[TLS_SLOT_THREAD_ID]; 98 thread->tls = tls; 99 __init_tls(thread); 100 101 if ((thread->internal_flags & kPthreadInitFailed) != 0) { 102 pthread_exit(NULL); 103 } 104 105 void* result = func(arg); 106 pthread_exit(result); 107 } 108 109 __LIBC_ABI_PRIVATE__ 110 int _init_thread(pthread_internal_t* thread, bool add_to_thread_list) { 111 int error = 0; 112 113 // Set the scheduling policy/priority of the thread. 114 if (thread->attr.sched_policy != SCHED_NORMAL) { 115 struct sched_param param; 116 param.sched_priority = thread->attr.sched_priority; 117 if (sched_setscheduler(thread->tid, thread->attr.sched_policy, ¶m) == -1) { 118 // For backwards compatibility reasons, we just warn about failures here. 119 // error = errno; 120 __libc_format_log(ANDROID_LOG_WARN, "libc", 121 "pthread_create sched_setscheduler call failed: %s", strerror(errno)); 122 } 123 } 124 125 pthread_cond_init(&thread->join_cond, NULL); 126 thread->cleanup_stack = NULL; 127 128 if (add_to_thread_list) { 129 _pthread_internal_add(thread); 130 } 131 132 return error; 133 } 134 135 static void* __create_thread_stack(pthread_internal_t* thread) { 136 ScopedPthreadMutexLocker lock(&gPthreadStackCreationLock); 137 138 // Create a new private anonymous map. 139 int prot = PROT_READ | PROT_WRITE; 140 int flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE; 141 void* stack = mmap(NULL, thread->attr.stack_size, prot, flags, -1, 0); 142 if (stack == MAP_FAILED) { 143 __libc_format_log(ANDROID_LOG_WARN, 144 "libc", 145 "pthread_create failed: couldn't allocate %zd-byte stack: %s", 146 thread->attr.stack_size, strerror(errno)); 147 return NULL; 148 } 149 150 // Set the guard region at the end of the stack to PROT_NONE. 151 if (mprotect(stack, thread->attr.guard_size, PROT_NONE) == -1) { 152 __libc_format_log(ANDROID_LOG_WARN, "libc", 153 "pthread_create failed: couldn't mprotect PROT_NONE %zd-byte stack guard region: %s", 154 thread->attr.guard_size, strerror(errno)); 155 munmap(stack, thread->attr.stack_size); 156 return NULL; 157 } 158 159 return stack; 160 } 161 162 int 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_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 void** tls = (void**)((uint8_t*)(thread->attr.stack_base) + thread->attr.stack_size - BIONIC_TLS_SLOTS * sizeof(void*)); 208 void* child_stack = tls; 209 210 // Create a mutex for the thread in TLS_SLOT_SELF 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*) &tls[TLS_SLOT_SELF]; 217 pthread_mutex_init(start_mutex, NULL); 218 ScopedPthreadMutexLocker start_locker(start_mutex); 219 220 tls[TLS_SLOT_THREAD_ID] = thread; 221 222 int flags = CLONE_FILES | CLONE_FS | CLONE_VM | CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM; 223 224 int tid = __pthread_clone(start_routine, child_stack, flags, arg); 225 if (tid < 0) { 226 int clone_errno = errno; 227 if ((thread->attr.flags & PTHREAD_ATTR_FLAG_USER_STACK) == 0) { 228 munmap(thread->attr.stack_base, thread->attr.stack_size); 229 } 230 free(thread); 231 __libc_format_log(ANDROID_LOG_WARN, "libc", "pthread_create failed: clone failed: %s", strerror(errno)); 232 return clone_errno; 233 } 234 235 thread->tid = tid; 236 237 int init_errno = _init_thread(thread, true); 238 if (init_errno != 0) { 239 // Mark the thread detached and let its __thread_entry run to 240 // completion. (It'll just exit immediately, cleaning up its resources.) 241 thread->internal_flags |= kPthreadInitFailed; 242 thread->attr.flags |= PTHREAD_ATTR_FLAG_DETACHED; 243 return init_errno; 244 } 245 246 // Notify any debuggers about the new thread. 247 { 248 ScopedPthreadMutexLocker debugger_locker(&gDebuggerNotificationLock); 249 _thread_created_hook(thread->tid); 250 } 251 252 // Publish the pthread_t and let the thread run. 253 *thread_out = (pthread_t) thread; 254 255 return 0; 256 } 257
