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 #include <unistd.h> 34 35 #include "pthread_internal.h" 36 37 #include "private/bionic_macros.h" 38 #include "private/bionic_ssp.h" 39 #include "private/bionic_tls.h" 40 #include "private/libc_logging.h" 41 #include "private/ErrnoRestorer.h" 42 #include "private/ScopedPthreadMutexLocker.h" 43 44 // x86 uses segment descriptors rather than a direct pointer to TLS. 45 #if __i386__ 46 #include <asm/ldt.h> 47 extern "C" __LIBC_HIDDEN__ void __init_user_desc(struct user_desc*, int, void*); 48 #endif 49 50 extern "C" int __isthreaded; 51 52 // This code is used both by each new pthread and the code that initializes the main thread. 53 void __init_tls(pthread_internal_t* thread) { 54 if (thread->user_allocated_stack()) { 55 // We don't know where the user got their stack, so assume the worst and zero the TLS area. 56 memset(&thread->tls[0], 0, BIONIC_TLS_SLOTS * sizeof(void*)); 57 } 58 59 // Slot 0 must point to itself. The x86 Linux kernel reads the TLS from %fs:0. 60 thread->tls[TLS_SLOT_SELF] = thread->tls; 61 thread->tls[TLS_SLOT_THREAD_ID] = thread; 62 // GCC looks in the TLS for the stack guard on x86, so copy it there from our global. 63 thread->tls[TLS_SLOT_STACK_GUARD] = (void*) __stack_chk_guard; 64 } 65 66 void __init_alternate_signal_stack(pthread_internal_t* thread) { 67 // Create and set an alternate signal stack. 68 stack_t ss; 69 ss.ss_sp = mmap(NULL, SIGSTKSZ, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); 70 if (ss.ss_sp != MAP_FAILED) { 71 ss.ss_size = SIGSTKSZ; 72 ss.ss_flags = 0; 73 sigaltstack(&ss, NULL); 74 thread->alternate_signal_stack = ss.ss_sp; 75 } 76 } 77 78 int __init_thread(pthread_internal_t* thread, bool add_to_thread_list) { 79 int error = 0; 80 81 // Set the scheduling policy/priority of the thread. 82 if (thread->attr.sched_policy != SCHED_NORMAL) { 83 sched_param param; 84 param.sched_priority = thread->attr.sched_priority; 85 if (sched_setscheduler(thread->tid, thread->attr.sched_policy, ¶m) == -1) { 86 #if __LP64__ 87 // For backwards compatibility reasons, we only report failures on 64-bit devices. 88 error = errno; 89 #endif 90 __libc_format_log(ANDROID_LOG_WARN, "libc", 91 "pthread_create sched_setscheduler call failed: %s", strerror(errno)); 92 } 93 } 94 95 thread->cleanup_stack = NULL; 96 97 if (add_to_thread_list) { 98 _pthread_internal_add(thread); 99 } 100 101 return error; 102 } 103 104 static void* __create_thread_stack(pthread_internal_t* thread) { 105 // Create a new private anonymous map. 106 int prot = PROT_READ | PROT_WRITE; 107 int flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE; 108 void* stack = mmap(NULL, thread->attr.stack_size, prot, flags, -1, 0); 109 if (stack == MAP_FAILED) { 110 __libc_format_log(ANDROID_LOG_WARN, 111 "libc", 112 "pthread_create failed: couldn't allocate %zd-byte stack: %s", 113 thread->attr.stack_size, strerror(errno)); 114 return NULL; 115 } 116 117 // Set the guard region at the end of the stack to PROT_NONE. 118 if (mprotect(stack, thread->attr.guard_size, PROT_NONE) == -1) { 119 __libc_format_log(ANDROID_LOG_WARN, "libc", 120 "pthread_create failed: couldn't mprotect PROT_NONE %zd-byte stack guard region: %s", 121 thread->attr.guard_size, strerror(errno)); 122 munmap(stack, thread->attr.stack_size); 123 return NULL; 124 } 125 126 return stack; 127 } 128 129 static int __pthread_start(void* arg) { 130 pthread_internal_t* thread = reinterpret_cast<pthread_internal_t*>(arg); 131 132 // Wait for our creating thread to release us. This lets it have time to 133 // notify gdb about this thread before we start doing anything. 134 // This also provides the memory barrier needed to ensure that all memory 135 // accesses previously made by the creating thread are visible to us. 136 pthread_mutex_lock(&thread->startup_handshake_mutex); 137 pthread_mutex_destroy(&thread->startup_handshake_mutex); 138 139 __init_alternate_signal_stack(thread); 140 141 void* result = thread->start_routine(thread->start_routine_arg); 142 pthread_exit(result); 143 144 return 0; 145 } 146 147 // A dummy start routine for pthread_create failures where we've created a thread but aren't 148 // going to run user code on it. We swap out the user's start routine for this and take advantage 149 // of the regular thread teardown to free up resources. 150 static void* __do_nothing(void*) { 151 return NULL; 152 } 153 154 int pthread_create(pthread_t* thread_out, pthread_attr_t const* attr, 155 void* (*start_routine)(void*), void* arg) { 156 ErrnoRestorer errno_restorer; 157 158 // Inform the rest of the C library that at least one thread was created. 159 __isthreaded = 1; 160 161 pthread_internal_t* thread = reinterpret_cast<pthread_internal_t*>(calloc(sizeof(*thread), 1)); 162 if (thread == NULL) { 163 __libc_format_log(ANDROID_LOG_WARN, "libc", "pthread_create failed: couldn't allocate thread"); 164 return EAGAIN; 165 } 166 167 if (attr == NULL) { 168 pthread_attr_init(&thread->attr); 169 } else { 170 thread->attr = *attr; 171 attr = NULL; // Prevent misuse below. 172 } 173 174 // Make sure the stack size and guard size are multiples of PAGE_SIZE. 175 thread->attr.stack_size = BIONIC_ALIGN(thread->attr.stack_size, PAGE_SIZE); 176 thread->attr.guard_size = BIONIC_ALIGN(thread->attr.guard_size, PAGE_SIZE); 177 178 if (thread->attr.stack_base == NULL) { 179 // The caller didn't provide a stack, so allocate one. 180 thread->attr.stack_base = __create_thread_stack(thread); 181 if (thread->attr.stack_base == NULL) { 182 free(thread); 183 return EAGAIN; 184 } 185 } else { 186 // The caller did provide a stack, so remember we're not supposed to free it. 187 thread->attr.flags |= PTHREAD_ATTR_FLAG_USER_ALLOCATED_STACK; 188 } 189 190 // Make room for the TLS area. 191 // The child stack is the same address, just growing in the opposite direction. 192 // At offsets >= 0, we have the TLS slots. 193 // At offsets < 0, we have the child stack. 194 thread->tls = reinterpret_cast<void**>(reinterpret_cast<uint8_t*>(thread->attr.stack_base) + 195 thread->attr.stack_size - BIONIC_TLS_SLOTS * sizeof(void*)); 196 void* child_stack = thread->tls; 197 __init_tls(thread); 198 199 // Create a mutex for the thread in TLS to wait on once it starts so we can keep 200 // it from doing anything until after we notify the debugger about it 201 // 202 // This also provides the memory barrier we need to ensure that all 203 // memory accesses previously performed by this thread are visible to 204 // the new thread. 205 pthread_mutex_init(&thread->startup_handshake_mutex, NULL); 206 pthread_mutex_lock(&thread->startup_handshake_mutex); 207 208 thread->start_routine = start_routine; 209 thread->start_routine_arg = arg; 210 211 thread->set_cached_pid(getpid()); 212 213 int flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM | 214 CLONE_SETTLS | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID; 215 void* tls = thread->tls; 216 #if defined(__i386__) 217 // On x86 (but not x86-64), CLONE_SETTLS takes a pointer to a struct user_desc rather than 218 // a pointer to the TLS itself. 219 user_desc tls_descriptor; 220 __init_user_desc(&tls_descriptor, false, tls); 221 tls = &tls_descriptor; 222 #endif 223 int rc = clone(__pthread_start, child_stack, flags, thread, &(thread->tid), tls, &(thread->tid)); 224 if (rc == -1) { 225 int clone_errno = errno; 226 // We don't have to unlock the mutex at all because clone(2) failed so there's no child waiting to 227 // be unblocked, but we're about to unmap the memory the mutex is stored in, so this serves as a 228 // reminder that you can't rewrite this function to use a ScopedPthreadMutexLocker. 229 pthread_mutex_unlock(&thread->startup_handshake_mutex); 230 if (!thread->user_allocated_stack()) { 231 munmap(thread->attr.stack_base, thread->attr.stack_size); 232 } 233 free(thread); 234 __libc_format_log(ANDROID_LOG_WARN, "libc", "pthread_create failed: clone failed: %s", strerror(errno)); 235 return clone_errno; 236 } 237 238 int init_errno = __init_thread(thread, true); 239 if (init_errno != 0) { 240 // Mark the thread detached and replace its start_routine with a no-op. 241 // Letting the thread run is the easiest way to clean up its resources. 242 thread->attr.flags |= PTHREAD_ATTR_FLAG_DETACHED; 243 thread->start_routine = __do_nothing; 244 pthread_mutex_unlock(&thread->startup_handshake_mutex); 245 return init_errno; 246 } 247 248 // Publish the pthread_t and unlock the mutex to let the new thread start running. 249 *thread_out = reinterpret_cast<pthread_t>(thread); 250 pthread_mutex_unlock(&thread->startup_handshake_mutex); 251 252 return 0; 253 } 254
