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 <string.h> 33 #include <sys/mman.h> 34 #include <unistd.h> 35 36 #include "pthread_internal.h" 37 38 #include "private/bionic_macros.h" 39 #include "private/bionic_prctl.h" 40 #include "private/bionic_ssp.h" 41 #include "private/bionic_tls.h" 42 #include "private/libc_logging.h" 43 #include "private/ErrnoRestorer.h" 44 #include "private/ScopedPthreadMutexLocker.h" 45 46 // x86 uses segment descriptors rather than a direct pointer to TLS. 47 #if __i386__ 48 #include <asm/ldt.h> 49 extern "C" __LIBC_HIDDEN__ void __init_user_desc(struct user_desc*, int, void*); 50 #endif 51 52 extern "C" int __isthreaded; 53 54 // This code is used both by each new pthread and the code that initializes the main thread. 55 void __init_tls(pthread_internal_t* thread) { 56 // Slot 0 must point to itself. The x86 Linux kernel reads the TLS from %fs:0. 57 thread->tls[TLS_SLOT_SELF] = thread->tls; 58 thread->tls[TLS_SLOT_THREAD_ID] = thread; 59 // GCC looks in the TLS for the stack guard on x86, so copy it there from our global. 60 thread->tls[TLS_SLOT_STACK_GUARD] = reinterpret_cast<void*>(__stack_chk_guard); 61 } 62 63 void __init_alternate_signal_stack(pthread_internal_t* thread) { 64 // Create and set an alternate signal stack. 65 void* stack_base = mmap(NULL, SIGNAL_STACK_SIZE, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); 66 if (stack_base != MAP_FAILED) { 67 68 // Create a guard page to catch stack overflows in signal handlers. 69 if (mprotect(stack_base, PAGE_SIZE, PROT_NONE) == -1) { 70 munmap(stack_base, SIGNAL_STACK_SIZE); 71 return; 72 } 73 stack_t ss; 74 ss.ss_sp = reinterpret_cast<uint8_t*>(stack_base) + PAGE_SIZE; 75 ss.ss_size = SIGNAL_STACK_SIZE - PAGE_SIZE; 76 ss.ss_flags = 0; 77 sigaltstack(&ss, NULL); 78 thread->alternate_signal_stack = stack_base; 79 80 // We can only use const static allocated string for mapped region name, as Android kernel 81 // uses the string pointer directly when dumping /proc/pid/maps. 82 prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, ss.ss_sp, ss.ss_size, "thread signal stack"); 83 prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, stack_base, PAGE_SIZE, "thread signal stack guard page"); 84 } 85 } 86 87 int __init_thread(pthread_internal_t* thread) { 88 int error = 0; 89 90 if (__predict_true((thread->attr.flags & PTHREAD_ATTR_FLAG_DETACHED) == 0)) { 91 atomic_init(&thread->join_state, THREAD_NOT_JOINED); 92 } else { 93 atomic_init(&thread->join_state, THREAD_DETACHED); 94 } 95 96 // Set the scheduling policy/priority of the thread. 97 if (thread->attr.sched_policy != SCHED_NORMAL) { 98 sched_param param; 99 param.sched_priority = thread->attr.sched_priority; 100 if (sched_setscheduler(thread->tid, thread->attr.sched_policy, ¶m) == -1) { 101 #if __LP64__ 102 // For backwards compatibility reasons, we only report failures on 64-bit devices. 103 error = errno; 104 #endif 105 __libc_format_log(ANDROID_LOG_WARN, "libc", 106 "pthread_create sched_setscheduler call failed: %s", strerror(errno)); 107 } 108 } 109 110 thread->cleanup_stack = NULL; 111 112 return error; 113 } 114 115 static void* __create_thread_mapped_space(size_t mmap_size, size_t stack_guard_size) { 116 // Create a new private anonymous map. 117 int prot = PROT_READ | PROT_WRITE; 118 int flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE; 119 void* space = mmap(NULL, mmap_size, prot, flags, -1, 0); 120 if (space == MAP_FAILED) { 121 __libc_format_log(ANDROID_LOG_WARN, 122 "libc", 123 "pthread_create failed: couldn't allocate %zu-bytes mapped space: %s", 124 mmap_size, strerror(errno)); 125 return NULL; 126 } 127 128 // Stack is at the lower end of mapped space, stack guard region is at the lower end of stack. 129 // Set the stack guard region to PROT_NONE, so we can detect thread stack overflow. 130 if (mprotect(space, stack_guard_size, PROT_NONE) == -1) { 131 __libc_format_log(ANDROID_LOG_WARN, "libc", 132 "pthread_create failed: couldn't mprotect PROT_NONE %zu-byte stack guard region: %s", 133 stack_guard_size, strerror(errno)); 134 munmap(space, mmap_size); 135 return NULL; 136 } 137 prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, space, stack_guard_size, "thread stack guard page"); 138 139 return space; 140 } 141 142 static int __allocate_thread(pthread_attr_t* attr, pthread_internal_t** threadp, void** child_stack) { 143 size_t mmap_size; 144 uint8_t* stack_top; 145 146 if (attr->stack_base == NULL) { 147 // The caller didn't provide a stack, so allocate one. 148 // Make sure the stack size and guard size are multiples of PAGE_SIZE. 149 mmap_size = BIONIC_ALIGN(attr->stack_size + sizeof(pthread_internal_t), PAGE_SIZE); 150 attr->guard_size = BIONIC_ALIGN(attr->guard_size, PAGE_SIZE); 151 attr->stack_base = __create_thread_mapped_space(mmap_size, attr->guard_size); 152 if (attr->stack_base == NULL) { 153 return EAGAIN; 154 } 155 stack_top = reinterpret_cast<uint8_t*>(attr->stack_base) + mmap_size; 156 } else { 157 // Remember the mmap size is zero and we don't need to free it. 158 mmap_size = 0; 159 stack_top = reinterpret_cast<uint8_t*>(attr->stack_base) + attr->stack_size; 160 } 161 162 // Mapped space(or user allocated stack) is used for: 163 // pthread_internal_t 164 // thread stack (including guard page) 165 166 // To safely access the pthread_internal_t and thread stack, we need to find a 16-byte aligned boundary. 167 stack_top = reinterpret_cast<uint8_t*>( 168 (reinterpret_cast<uintptr_t>(stack_top) - sizeof(pthread_internal_t)) & ~0xf); 169 170 pthread_internal_t* thread = reinterpret_cast<pthread_internal_t*>(stack_top); 171 if (mmap_size == 0) { 172 // If thread was not allocated by mmap(), it may not have been cleared to zero. 173 // So assume the worst and zero it. 174 memset(thread, 0, sizeof(pthread_internal_t)); 175 } 176 attr->stack_size = stack_top - reinterpret_cast<uint8_t*>(attr->stack_base); 177 178 thread->mmap_size = mmap_size; 179 thread->attr = *attr; 180 __init_tls(thread); 181 182 *threadp = thread; 183 *child_stack = stack_top; 184 return 0; 185 } 186 187 static int __pthread_start(void* arg) { 188 pthread_internal_t* thread = reinterpret_cast<pthread_internal_t*>(arg); 189 190 // Wait for our creating thread to release us. This lets it have time to 191 // notify gdb about this thread before we start doing anything. 192 // This also provides the memory barrier needed to ensure that all memory 193 // accesses previously made by the creating thread are visible to us. 194 thread->startup_handshake_lock.lock(); 195 196 __init_alternate_signal_stack(thread); 197 198 void* result = thread->start_routine(thread->start_routine_arg); 199 pthread_exit(result); 200 201 return 0; 202 } 203 204 // A dummy start routine for pthread_create failures where we've created a thread but aren't 205 // going to run user code on it. We swap out the user's start routine for this and take advantage 206 // of the regular thread teardown to free up resources. 207 static void* __do_nothing(void*) { 208 return NULL; 209 } 210 211 int pthread_create(pthread_t* thread_out, pthread_attr_t const* attr, 212 void* (*start_routine)(void*), void* arg) { 213 ErrnoRestorer errno_restorer; 214 215 // Inform the rest of the C library that at least one thread was created. 216 __isthreaded = 1; 217 218 pthread_attr_t thread_attr; 219 if (attr == NULL) { 220 pthread_attr_init(&thread_attr); 221 } else { 222 thread_attr = *attr; 223 attr = NULL; // Prevent misuse below. 224 } 225 226 pthread_internal_t* thread = NULL; 227 void* child_stack = NULL; 228 int result = __allocate_thread(&thread_attr, &thread, &child_stack); 229 if (result != 0) { 230 return result; 231 } 232 233 // Create a lock for the thread to wait on once it starts so we can keep 234 // it from doing anything until after we notify the debugger about it 235 // 236 // This also provides the memory barrier we need to ensure that all 237 // memory accesses previously performed by this thread are visible to 238 // the new thread. 239 thread->startup_handshake_lock.init(false); 240 thread->startup_handshake_lock.lock(); 241 242 thread->start_routine = start_routine; 243 thread->start_routine_arg = arg; 244 245 thread->set_cached_pid(getpid()); 246 247 int flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM | 248 CLONE_SETTLS | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID; 249 void* tls = reinterpret_cast<void*>(thread->tls); 250 #if defined(__i386__) 251 // On x86 (but not x86-64), CLONE_SETTLS takes a pointer to a struct user_desc rather than 252 // a pointer to the TLS itself. 253 user_desc tls_descriptor; 254 __init_user_desc(&tls_descriptor, false, tls); 255 tls = &tls_descriptor; 256 #endif 257 int rc = clone(__pthread_start, child_stack, flags, thread, &(thread->tid), tls, &(thread->tid)); 258 if (rc == -1) { 259 int clone_errno = errno; 260 // We don't have to unlock the mutex at all because clone(2) failed so there's no child waiting to 261 // be unblocked, but we're about to unmap the memory the mutex is stored in, so this serves as a 262 // reminder that you can't rewrite this function to use a ScopedPthreadMutexLocker. 263 thread->startup_handshake_lock.unlock(); 264 if (thread->mmap_size != 0) { 265 munmap(thread->attr.stack_base, thread->mmap_size); 266 } 267 __libc_format_log(ANDROID_LOG_WARN, "libc", "pthread_create failed: clone failed: %s", strerror(errno)); 268 return clone_errno; 269 } 270 271 int init_errno = __init_thread(thread); 272 if (init_errno != 0) { 273 // Mark the thread detached and replace its start_routine with a no-op. 274 // Letting the thread run is the easiest way to clean up its resources. 275 atomic_store(&thread->join_state, THREAD_DETACHED); 276 __pthread_internal_add(thread); 277 thread->start_routine = __do_nothing; 278 thread->startup_handshake_lock.unlock(); 279 return init_errno; 280 } 281 282 // Publish the pthread_t and unlock the mutex to let the new thread start running. 283 *thread_out = __pthread_internal_add(thread); 284 thread->startup_handshake_lock.unlock(); 285 286 return 0; 287 } 288
