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      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 
     74 // This trampoline is called from the assembly _pthread_clone() function.
     75 extern "C" void __thread_entry(void* (*func)(void*), void* arg, void** tls) {
     76   // Wait for our creating thread to release us. This lets it have time to
     77   // notify gdb about this thread before we start doing anything.
     78   // This also provides the memory barrier needed to ensure that all memory
     79   // accesses previously made by the creating thread are visible to us.
     80   pthread_mutex_t* start_mutex = (pthread_mutex_t*) &tls[TLS_SLOT_SELF];
     81   pthread_mutex_lock(start_mutex);
     82   pthread_mutex_destroy(start_mutex);
     83 
     84   pthread_internal_t* thread = (pthread_internal_t*) tls[TLS_SLOT_THREAD_ID];
     85   thread->tls = tls;
     86   __init_tls(thread);
     87 
     88   if ((thread->internal_flags & kPthreadInitFailed) != 0) {
     89     pthread_exit(NULL);
     90   }
     91 
     92   void* result = func(arg);
     93   pthread_exit(result);
     94 }
     95 
     96 __LIBC_ABI_PRIVATE__
     97 int _init_thread(pthread_internal_t* thread, bool add_to_thread_list) {
     98   int error = 0;
     99 
    100   // Set the scheduling policy/priority of the thread.
    101   if (thread->attr.sched_policy != SCHED_NORMAL) {
    102     struct sched_param param;
    103     param.sched_priority = thread->attr.sched_priority;
    104     if (sched_setscheduler(thread->tid, thread->attr.sched_policy, &param) == -1) {
    105       // For backwards compatibility reasons, we just warn about failures here.
    106       // error = errno;
    107       const char* msg = "pthread_create sched_setscheduler call failed: %s\n";
    108       __libc_format_log(ANDROID_LOG_WARN, "libc", msg, strerror(errno));
    109     }
    110   }
    111 
    112   pthread_cond_init(&thread->join_cond, NULL);
    113   thread->join_count = 0;
    114   thread->cleanup_stack = NULL;
    115 
    116   if (add_to_thread_list) {
    117     _pthread_internal_add(thread);
    118   }
    119 
    120   return error;
    121 }
    122 
    123 static void* __create_thread_stack(size_t stack_size, size_t guard_size) {
    124   ScopedPthreadMutexLocker lock(&gPthreadStackCreationLock);
    125 
    126   // Create a new private anonymous map.
    127   int prot = PROT_READ | PROT_WRITE;
    128   int flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE;
    129   void* stack = mmap(NULL, stack_size, prot, flags, -1, 0);
    130   if (stack == MAP_FAILED) {
    131     return NULL;
    132   }
    133 
    134   // Set the guard region at the end of the stack to PROT_NONE.
    135   if (mprotect(stack, guard_size, PROT_NONE) == -1) {
    136     munmap(stack, stack_size);
    137     return NULL;
    138   }
    139 
    140   return stack;
    141 }
    142 
    143 int pthread_create(pthread_t* thread_out, pthread_attr_t const* attr,
    144                    void* (*start_routine)(void*), void* arg) {
    145   ErrnoRestorer errno_restorer;
    146 
    147   // Inform the rest of the C library that at least one thread
    148   // was created. This will enforce certain functions to acquire/release
    149   // locks (e.g. atexit()) to protect shared global structures.
    150   // This works because pthread_create() is not called by the C library
    151   // initialization routine that sets up the main thread's data structures.
    152   __isthreaded = 1;
    153 
    154   pthread_internal_t* thread = reinterpret_cast<pthread_internal_t*>(calloc(sizeof(*thread), 1));
    155   if (thread == NULL) {
    156     __libc_format_log(ANDROID_LOG_WARN, "libc", "pthread_create failed: couldn't allocate thread");
    157     return EAGAIN;
    158   }
    159   thread->allocated_on_heap = true;
    160 
    161   if (attr == NULL) {
    162     pthread_attr_init(&thread->attr);
    163   } else {
    164     thread->attr = *attr;
    165     attr = NULL; // Prevent misuse below.
    166   }
    167 
    168   // Make sure the stack size is PAGE_SIZE aligned.
    169   size_t stack_size = (thread->attr.stack_size + (PAGE_SIZE-1)) & ~(PAGE_SIZE-1);
    170 
    171   if (thread->attr.stack_base == NULL) {
    172     // The caller didn't provide a stack, so allocate one.
    173     thread->attr.stack_base = __create_thread_stack(stack_size, thread->attr.guard_size);
    174     if (thread->attr.stack_base == NULL) {
    175       free(thread);
    176       __libc_format_log(ANDROID_LOG_WARN, "libc", "pthread_create failed: couldn't allocate %zd-byte stack", stack_size);
    177       return EAGAIN;
    178     }
    179   } else {
    180     // The caller did provide a stack, so remember we're not supposed to free it.
    181     thread->attr.flags |= PTHREAD_ATTR_FLAG_USER_STACK;
    182   }
    183 
    184   // Make room for TLS.
    185   void** tls = (void**)((uint8_t*)(thread->attr.stack_base) + stack_size - BIONIC_TLS_SLOTS * sizeof(void*));
    186 
    187   // Create a mutex for the thread in TLS_SLOT_SELF to wait on once it starts so we can keep
    188   // it from doing anything until after we notify the debugger about it
    189   //
    190   // This also provides the memory barrier we need to ensure that all
    191   // memory accesses previously performed by this thread are visible to
    192   // the new thread.
    193   pthread_mutex_t* start_mutex = (pthread_mutex_t*) &tls[TLS_SLOT_SELF];
    194   pthread_mutex_init(start_mutex, NULL);
    195   ScopedPthreadMutexLocker start_locker(start_mutex);
    196 
    197   tls[TLS_SLOT_THREAD_ID] = thread;
    198 
    199   int flags = CLONE_FILES | CLONE_FS | CLONE_VM | CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM;
    200 
    201   int tid = __pthread_clone(start_routine, tls, flags, arg);
    202   if (tid < 0) {
    203     int clone_errno = errno;
    204     if ((thread->attr.flags & PTHREAD_ATTR_FLAG_USER_STACK) == 0) {
    205       munmap(thread->attr.stack_base, stack_size);
    206     }
    207     free(thread);
    208     __libc_format_log(ANDROID_LOG_WARN, "libc", "pthread_create failed: clone failed: %s", strerror(errno));
    209     return clone_errno;
    210   }
    211 
    212   thread->tid = tid;
    213 
    214   int init_errno = _init_thread(thread, true);
    215   if (init_errno != 0) {
    216     // Mark the thread detached and let its __thread_entry run to
    217     // completion. (It'll just exit immediately, cleaning up its resources.)
    218     thread->internal_flags |= kPthreadInitFailed;
    219     thread->attr.flags |= PTHREAD_ATTR_FLAG_DETACHED;
    220     return init_errno;
    221   }
    222 
    223   // Notify any debuggers about the new thread.
    224   {
    225     ScopedPthreadMutexLocker debugger_locker(&gDebuggerNotificationLock);
    226     _thread_created_hook(thread->tid);
    227   }
    228 
    229   // Publish the pthread_t and let the thread run.
    230   *thread_out = (pthread_t) thread;
    231 
    232   return 0;
    233 }
    234