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 45// x86 uses segment descriptors rather than a direct pointer to TLS. 46#if defined(__i386__) 47#include <asm/ldt.h> 48void __init_user_desc(struct user_desc*, bool, void*); 49#endif 50 51extern "C" int __isthreaded; 52 53// This code is used both by each new pthread and the code that initializes the main thread. 54void __init_tls(pthread_internal_t* thread) { 55 // Slot 0 must point to itself. The x86 Linux kernel reads the TLS from %fs:0. 56 thread->tls[TLS_SLOT_SELF] = thread->tls; 57 thread->tls[TLS_SLOT_THREAD_ID] = thread; 58 59 // Add a guard page before and after. 60 size_t allocation_size = BIONIC_TLS_SIZE + 2 * PAGE_SIZE; 61 void* allocation = mmap(nullptr, allocation_size, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); 62 if (allocation == MAP_FAILED) { 63 __libc_fatal("failed to allocate TLS"); 64 } 65 prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, allocation, allocation_size, "bionic TLS guard page"); 66 67 thread->bionic_tls = reinterpret_cast<bionic_tls*>(static_cast<char*>(allocation) + PAGE_SIZE); 68 if (mprotect(thread->bionic_tls, BIONIC_TLS_SIZE, PROT_READ | PROT_WRITE) != 0) { 69 __libc_fatal("failed to mprotect TLS"); 70 } 71 prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, thread->bionic_tls, BIONIC_TLS_SIZE, "bionic TLS"); 72} 73 74void __init_thread_stack_guard(pthread_internal_t* thread) { 75 // GCC looks in the TLS for the stack guard on x86, so copy it there from our global. 76 thread->tls[TLS_SLOT_STACK_GUARD] = reinterpret_cast<void*>(__stack_chk_guard); 77} 78 79void __init_alternate_signal_stack(pthread_internal_t* thread) { 80 // Create and set an alternate signal stack. 81 void* stack_base = mmap(NULL, SIGNAL_STACK_SIZE, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); 82 if (stack_base != MAP_FAILED) { 83 84 // Create a guard page to catch stack overflows in signal handlers. 85 if (mprotect(stack_base, PAGE_SIZE, PROT_NONE) == -1) { 86 munmap(stack_base, SIGNAL_STACK_SIZE); 87 return; 88 } 89 stack_t ss; 90 ss.ss_sp = reinterpret_cast<uint8_t*>(stack_base) + PAGE_SIZE; 91 ss.ss_size = SIGNAL_STACK_SIZE - PAGE_SIZE; 92 ss.ss_flags = 0; 93 sigaltstack(&ss, NULL); 94 thread->alternate_signal_stack = stack_base; 95 96 // We can only use const static allocated string for mapped region name, as Android kernel 97 // uses the string pointer directly when dumping /proc/pid/maps. 98 prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, ss.ss_sp, ss.ss_size, "thread signal stack"); 99 prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, stack_base, PAGE_SIZE, "thread signal stack guard page"); 100 } 101} 102 103int __init_thread(pthread_internal_t* thread) { 104 int error = 0; 105 106 if (__predict_true((thread->attr.flags & PTHREAD_ATTR_FLAG_DETACHED) == 0)) { 107 atomic_init(&thread->join_state, THREAD_NOT_JOINED); 108 } else { 109 atomic_init(&thread->join_state, THREAD_DETACHED); 110 } 111 112 // Set the scheduling policy/priority of the thread. 113 if (thread->attr.sched_policy != SCHED_NORMAL) { 114 sched_param param; 115 param.sched_priority = thread->attr.sched_priority; 116 if (sched_setscheduler(thread->tid, thread->attr.sched_policy, ¶m) == -1) { 117#if defined(__LP64__) 118 // For backwards compatibility reasons, we only report failures on 64-bit devices. 119 error = errno; 120#endif 121 __libc_format_log(ANDROID_LOG_WARN, "libc", 122 "pthread_create sched_setscheduler call failed: %s", strerror(errno)); 123 } 124 } 125 126 thread->cleanup_stack = NULL; 127 128 return error; 129} 130 131static void* __create_thread_mapped_space(size_t mmap_size, size_t stack_guard_size) { 132 // Create a new private anonymous map. 133 int prot = PROT_READ | PROT_WRITE; 134 int flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE; 135 void* space = mmap(NULL, mmap_size, prot, flags, -1, 0); 136 if (space == MAP_FAILED) { 137 __libc_format_log(ANDROID_LOG_WARN, 138 "libc", 139 "pthread_create failed: couldn't allocate %zu-bytes mapped space: %s", 140 mmap_size, strerror(errno)); 141 return NULL; 142 } 143 144 // Stack is at the lower end of mapped space, stack guard region is at the lower end of stack. 145 // Set the stack guard region to PROT_NONE, so we can detect thread stack overflow. 146 if (mprotect(space, stack_guard_size, PROT_NONE) == -1) { 147 __libc_format_log(ANDROID_LOG_WARN, "libc", 148 "pthread_create failed: couldn't mprotect PROT_NONE %zu-byte stack guard region: %s", 149 stack_guard_size, strerror(errno)); 150 munmap(space, mmap_size); 151 return NULL; 152 } 153 prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, space, stack_guard_size, "thread stack guard page"); 154 155 return space; 156} 157 158static int __allocate_thread(pthread_attr_t* attr, pthread_internal_t** threadp, void** child_stack) { 159 size_t mmap_size; 160 uint8_t* stack_top; 161 162 if (attr->stack_base == NULL) { 163 // The caller didn't provide a stack, so allocate one. 164 // Make sure the stack size and guard size are multiples of PAGE_SIZE. 165 mmap_size = BIONIC_ALIGN(attr->stack_size + sizeof(pthread_internal_t), PAGE_SIZE); 166 attr->guard_size = BIONIC_ALIGN(attr->guard_size, PAGE_SIZE); 167 attr->stack_base = __create_thread_mapped_space(mmap_size, attr->guard_size); 168 if (attr->stack_base == NULL) { 169 return EAGAIN; 170 } 171 stack_top = reinterpret_cast<uint8_t*>(attr->stack_base) + mmap_size; 172 } else { 173 // Remember the mmap size is zero and we don't need to free it. 174 mmap_size = 0; 175 stack_top = reinterpret_cast<uint8_t*>(attr->stack_base) + attr->stack_size; 176 } 177 178 // Mapped space(or user allocated stack) is used for: 179 // pthread_internal_t 180 // thread stack (including guard page) 181 182 // To safely access the pthread_internal_t and thread stack, we need to find a 16-byte aligned boundary. 183 stack_top = reinterpret_cast<uint8_t*>( 184 (reinterpret_cast<uintptr_t>(stack_top) - sizeof(pthread_internal_t)) & ~0xf); 185 186 pthread_internal_t* thread = reinterpret_cast<pthread_internal_t*>(stack_top); 187 if (mmap_size == 0) { 188 // If thread was not allocated by mmap(), it may not have been cleared to zero. 189 // So assume the worst and zero it. 190 memset(thread, 0, sizeof(pthread_internal_t)); 191 } 192 attr->stack_size = stack_top - reinterpret_cast<uint8_t*>(attr->stack_base); 193 194 thread->mmap_size = mmap_size; 195 thread->attr = *attr; 196 __init_tls(thread); 197 __init_thread_stack_guard(thread); 198 199 *threadp = thread; 200 *child_stack = stack_top; 201 return 0; 202} 203 204static int __pthread_start(void* arg) { 205 pthread_internal_t* thread = reinterpret_cast<pthread_internal_t*>(arg); 206 207 // Wait for our creating thread to release us. This lets it have time to 208 // notify gdb about this thread before we start doing anything. 209 // This also provides the memory barrier needed to ensure that all memory 210 // accesses previously made by the creating thread are visible to us. 211 thread->startup_handshake_lock.lock(); 212 213 __init_alternate_signal_stack(thread); 214 215 void* result = thread->start_routine(thread->start_routine_arg); 216 pthread_exit(result); 217 218 return 0; 219} 220 221// A dummy start routine for pthread_create failures where we've created a thread but aren't 222// going to run user code on it. We swap out the user's start routine for this and take advantage 223// of the regular thread teardown to free up resources. 224static void* __do_nothing(void*) { 225 return NULL; 226} 227 228int pthread_create(pthread_t* thread_out, pthread_attr_t const* attr, 229 void* (*start_routine)(void*), void* arg) { 230 ErrnoRestorer errno_restorer; 231 232 // Inform the rest of the C library that at least one thread was created. 233 __isthreaded = 1; 234 235 pthread_attr_t thread_attr; 236 if (attr == NULL) { 237 pthread_attr_init(&thread_attr); 238 } else { 239 thread_attr = *attr; 240 attr = NULL; // Prevent misuse below. 241 } 242 243 pthread_internal_t* thread = NULL; 244 void* child_stack = NULL; 245 int result = __allocate_thread(&thread_attr, &thread, &child_stack); 246 if (result != 0) { 247 return result; 248 } 249 250 // Create a lock for the thread to wait on once it starts so we can keep 251 // it from doing anything until after we notify the debugger about it 252 // 253 // This also provides the memory barrier we need to ensure that all 254 // memory accesses previously performed by this thread are visible to 255 // the new thread. 256 thread->startup_handshake_lock.init(false); 257 thread->startup_handshake_lock.lock(); 258 259 thread->start_routine = start_routine; 260 thread->start_routine_arg = arg; 261 262 thread->set_cached_pid(getpid()); 263 264 int flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM | 265 CLONE_SETTLS | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID; 266 void* tls = reinterpret_cast<void*>(thread->tls); 267#if defined(__i386__) 268 // On x86 (but not x86-64), CLONE_SETTLS takes a pointer to a struct user_desc rather than 269 // a pointer to the TLS itself. 270 user_desc tls_descriptor; 271 __init_user_desc(&tls_descriptor, false, tls); 272 tls = &tls_descriptor; 273#endif 274 int rc = clone(__pthread_start, child_stack, flags, thread, &(thread->tid), tls, &(thread->tid)); 275 if (rc == -1) { 276 int clone_errno = errno; 277 // We don't have to unlock the mutex at all because clone(2) failed so there's no child waiting to 278 // be unblocked, but we're about to unmap the memory the mutex is stored in, so this serves as a 279 // reminder that you can't rewrite this function to use a ScopedPthreadMutexLocker. 280 thread->startup_handshake_lock.unlock(); 281 if (thread->mmap_size != 0) { 282 munmap(thread->attr.stack_base, thread->mmap_size); 283 } 284 __libc_format_log(ANDROID_LOG_WARN, "libc", "pthread_create failed: clone failed: %s", strerror(errno)); 285 return clone_errno; 286 } 287 288 int init_errno = __init_thread(thread); 289 if (init_errno != 0) { 290 // Mark the thread detached and replace its start_routine with a no-op. 291 // Letting the thread run is the easiest way to clean up its resources. 292 atomic_store(&thread->join_state, THREAD_DETACHED); 293 __pthread_internal_add(thread); 294 thread->start_routine = __do_nothing; 295 thread->startup_handshake_lock.unlock(); 296 return init_errno; 297 } 298 299 // Publish the pthread_t and unlock the mutex to let the new thread start running. 300 *thread_out = __pthread_internal_add(thread); 301 thread->startup_handshake_lock.unlock(); 302 303 return 0; 304} 305