1 | #define _GNU_SOURCE
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2 | #include "pthread_impl.h"
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3 | #include "stdio_impl.h"
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4 | #include "libc.h"
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5 | #include <sys/mman.h>
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6 | #include <string.h>
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7 | #include <stddef.h>
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8 |
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9 | void *__mmap(void *, size_t, int, int, int, off_t);
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10 | int __munmap(void *, size_t);
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11 | int __mprotect(void *, size_t, int);
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12 |
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13 | static void dummy_0()
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14 | {
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15 | }
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16 | weak_alias(dummy_0, __acquire_ptc);
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17 | weak_alias(dummy_0, __release_ptc);
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18 | weak_alias(dummy_0, __pthread_tsd_run_dtors);
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19 | weak_alias(dummy_0, __do_orphaned_stdio_locks);
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20 | weak_alias(dummy_0, __dl_thread_cleanup);
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21 |
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22 | _Noreturn void __pthread_exit(void *result)
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23 | {
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24 | pthread_t self = __pthread_self();
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25 | sigset_t set;
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26 |
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27 | self->canceldisable = 1;
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28 | self->cancelasync = 0;
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29 | self->result = result;
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30 |
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31 | while (self->cancelbuf) {
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32 | void (*f)(void *) = self->cancelbuf->__f;
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33 | void *x = self->cancelbuf->__x;
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34 | self->cancelbuf = self->cancelbuf->__next;
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35 | f(x);
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36 | }
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37 |
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38 | __pthread_tsd_run_dtors();
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39 |
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40 | __lock(self->exitlock);
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41 |
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42 | /* Mark this thread dead before decrementing count */
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43 | __lock(self->killlock);
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44 | self->dead = 1;
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45 |
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46 | /* Block all signals before decrementing the live thread count.
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47 | * This is important to ensure that dynamically allocated TLS
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48 | * is not under-allocated/over-committed, and possibly for other
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49 | * reasons as well. */
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50 | __block_all_sigs(&set);
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51 |
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52 | /* Wait to unlock the kill lock, which governs functions like
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53 | * pthread_kill which target a thread id, until signals have
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54 | * been blocked. This precludes observation of the thread id
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55 | * as a live thread (with application code running in it) after
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56 | * the thread was reported dead by ESRCH being returned. */
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57 | __unlock(self->killlock);
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58 |
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59 | /* It's impossible to determine whether this is "the last thread"
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60 | * until performing the atomic decrement, since multiple threads
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61 | * could exit at the same time. For the last thread, revert the
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62 | * decrement and unblock signals to give the atexit handlers and
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63 | * stdio cleanup code a consistent state. */
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64 | if (a_fetch_add(&libc.threads_minus_1, -1)==0) {
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65 | libc.threads_minus_1 = 0;
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66 | __restore_sigs(&set);
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67 | exit(0);
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68 | }
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69 |
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70 | /* Process robust list in userspace to handle non-pshared mutexes
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71 | * and the detached thread case where the robust list head will
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72 | * be invalid when the kernel would process it. */
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73 | __vm_lock();
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74 | volatile void *volatile *rp;
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75 | while ((rp=self->robust_list.head) && rp != &self->robust_list.head) {
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76 | pthread_mutex_t *m = (void *)((char *)rp
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77 | - offsetof(pthread_mutex_t, _m_next));
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78 | int waiters = m->_m_waiters;
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79 | int priv = (m->_m_type & 128) ^ 128;
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80 | self->robust_list.pending = rp;
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81 | self->robust_list.head = *rp;
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82 | int cont = a_swap(&m->_m_lock, 0x40000000);
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83 | self->robust_list.pending = 0;
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84 | if (cont < 0 || waiters)
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85 | __wake(&m->_m_lock, 1, priv);
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86 | }
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87 | __vm_unlock();
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88 |
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89 | __do_orphaned_stdio_locks();
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90 | __dl_thread_cleanup();
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91 |
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92 | if (self->detached && self->map_base) {
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93 | /* Detached threads must avoid the kernel clear_child_tid
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94 | * feature, since the virtual address will have been
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95 | * unmapped and possibly already reused by a new mapping
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96 | * at the time the kernel would perform the write. In
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97 | * the case of threads that started out detached, the
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98 | * initial clone flags are correct, but if the thread was
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99 | * detached later (== 2), we need to clear it here. */
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100 | if (self->detached == 2) __syscall(SYS_set_tid_address, 0);
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101 |
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102 | /* Robust list will no longer be valid, and was already
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103 | * processed above, so unregister it with the kernel. */
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104 | if (self->robust_list.off)
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105 | __syscall(SYS_set_robust_list, 0, 3*sizeof(long));
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106 |
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107 | /* Since __unmapself bypasses the normal munmap code path,
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108 | * explicitly wait for vmlock holders first. */
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109 | __vm_wait();
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110 |
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111 | /* The following call unmaps the thread's stack mapping
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112 | * and then exits without touching the stack. */
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113 | __unmapself(self->map_base, self->map_size);
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114 | }
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115 |
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116 | for (;;) __syscall(SYS_exit, 0);
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117 | }
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118 |
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119 | void __do_cleanup_push(struct __ptcb *cb)
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120 | {
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121 | struct pthread *self = __pthread_self();
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122 | cb->__next = self->cancelbuf;
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123 | self->cancelbuf = cb;
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124 | }
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125 |
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126 | void __do_cleanup_pop(struct __ptcb *cb)
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127 | {
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128 | __pthread_self()->cancelbuf = cb->__next;
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129 | }
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130 |
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131 | static int start(void *p)
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132 | {
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133 | pthread_t self = p;
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134 | /* States for startlock:
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135 | * 0 = no need for start sync
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136 | * 1 = waiting for parent to do work
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137 | * 2 = failure in parent, child must abort
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138 | * 3 = success in parent, child must restore sigmask */
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139 | if (self->startlock[0]) {
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140 | __wait(self->startlock, 0, 1, 1);
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141 | if (self->startlock[0] == 2) {
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142 | self->detached = 2;
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143 | pthread_exit(0);
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144 | }
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145 | __restore_sigs(self->sigmask);
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146 | }
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147 | if (self->unblock_cancel)
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148 | __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK,
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149 | SIGPT_SET, 0, _NSIG/8);
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150 | __pthread_exit(self->start(self->start_arg));
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151 | return 0;
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152 | }
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153 |
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154 | static int start_c11(void *p)
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155 | {
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156 | pthread_t self = p;
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157 | int (*start)(void*) = (int(*)(void*)) self->start;
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158 | __pthread_exit((void *)(uintptr_t)start(self->start_arg));
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159 | return 0;
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160 | }
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161 |
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162 | #define ROUND(x) (((x)+PAGE_SIZE-1)&-PAGE_SIZE)
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163 |
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164 | /* pthread_key_create.c overrides this */
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165 | static volatile size_t dummy = 0;
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166 | weak_alias(dummy, __pthread_tsd_size);
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167 | static void *dummy_tsd[1] = { 0 };
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168 | weak_alias(dummy_tsd, __pthread_tsd_main);
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169 |
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170 | volatile int __block_new_threads = 0;
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171 | size_t __default_stacksize = DEFAULT_STACK_SIZE;
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172 | size_t __default_guardsize = DEFAULT_GUARD_SIZE;
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173 |
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174 | static FILE *volatile dummy_file = 0;
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175 | weak_alias(dummy_file, __stdin_used);
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176 | weak_alias(dummy_file, __stdout_used);
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177 | weak_alias(dummy_file, __stderr_used);
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178 |
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179 | static void init_file_lock(FILE *f)
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180 | {
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181 | if (f && f->lock<0) f->lock = 0;
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182 | }
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183 |
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184 | void *__copy_tls(unsigned char *);
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185 |
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186 | int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attrp, void *(*entry)(void *), void *restrict arg)
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187 | {
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188 | int ret, c11 = (attrp == __ATTRP_C11_THREAD);
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189 | size_t size, guard;
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190 | struct pthread *self, *new;
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191 | unsigned char *map = 0, *stack = 0, *tsd = 0, *stack_limit;
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192 | unsigned flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND
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193 | | CLONE_THREAD | CLONE_SYSVSEM | CLONE_SETTLS
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194 | | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID | CLONE_DETACHED;
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195 | int do_sched = 0;
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196 | pthread_attr_t attr = { 0 };
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197 |
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198 | if (!libc.can_do_threads) return ENOSYS;
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199 | self = __pthread_self();
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200 | if (!libc.threaded) {
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201 | for (FILE *f=*__ofl_lock(); f; f=f->next)
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202 | init_file_lock(f);
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203 | __ofl_unlock();
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204 | init_file_lock(__stdin_used);
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205 | init_file_lock(__stdout_used);
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206 | init_file_lock(__stderr_used);
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207 | __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK, SIGPT_SET, 0, _NSIG/8);
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208 | self->tsd = (void **)__pthread_tsd_main;
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209 | libc.threaded = 1;
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210 | }
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211 | if (attrp && !c11) attr = *attrp;
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212 |
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213 | __acquire_ptc();
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214 | if (!attrp || c11) {
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215 | attr._a_stacksize = __default_stacksize;
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216 | attr._a_guardsize = __default_guardsize;
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217 | }
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218 |
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219 | if (__block_new_threads) __wait(&__block_new_threads, 0, 1, 1);
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220 |
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221 | if (attr._a_stackaddr) {
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222 | size_t need = libc.tls_size + __pthread_tsd_size;
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223 | size = attr._a_stacksize;
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224 | stack = (void *)(attr._a_stackaddr & -16);
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225 | stack_limit = (void *)(attr._a_stackaddr - size);
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226 | /* Use application-provided stack for TLS only when
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227 | * it does not take more than ~12% or 2k of the
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228 | * application's stack space. */
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229 | if (need < size/8 && need < 2048) {
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230 | tsd = stack - __pthread_tsd_size;
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231 | stack = tsd - libc.tls_size;
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232 | memset(stack, 0, need);
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233 | } else {
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234 | size = ROUND(need);
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235 | guard = 0;
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236 | }
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237 | } else {
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238 | guard = ROUND(attr._a_guardsize);
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239 | size = guard + ROUND(attr._a_stacksize
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240 | + libc.tls_size + __pthread_tsd_size);
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241 | }
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242 |
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243 | if (!tsd) {
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244 | if (guard) {
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245 | map = __mmap(0, size, PROT_NONE, MAP_PRIVATE|MAP_ANON, -1, 0);
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246 | if (map == MAP_FAILED) goto fail;
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247 | if (__mprotect(map+guard, size-guard, PROT_READ|PROT_WRITE)
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248 | && errno != ENOSYS) {
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249 | __munmap(map, size);
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250 | goto fail;
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251 | }
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252 | } else {
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253 | map = __mmap(0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0);
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254 | if (map == MAP_FAILED) goto fail;
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255 | }
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256 | tsd = map + size - __pthread_tsd_size;
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257 | if (!stack) {
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258 | stack = tsd - libc.tls_size;
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259 | stack_limit = map + guard;
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260 | }
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261 | }
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262 |
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263 | new = __copy_tls(tsd - libc.tls_size);
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264 | new->map_base = map;
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265 | new->map_size = size;
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266 | new->stack = stack;
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267 | new->stack_size = stack - stack_limit;
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268 | new->start = entry;
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269 | new->start_arg = arg;
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270 | new->self = new;
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271 | new->tsd = (void *)tsd;
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272 | new->locale = &libc.global_locale;
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273 | if (attr._a_detach) {
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274 | new->detached = 1;
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275 | flags -= CLONE_CHILD_CLEARTID;
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276 | }
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277 | if (attr._a_sched) {
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278 | do_sched = new->startlock[0] = 1;
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279 | __block_app_sigs(new->sigmask);
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280 | }
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281 | new->robust_list.head = &new->robust_list.head;
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282 | new->unblock_cancel = self->cancel;
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283 | new->CANARY = self->CANARY;
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284 |
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285 | a_inc(&libc.threads_minus_1);
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286 | ret = __clone((c11 ? start_c11 : start), stack, flags, new, &new->tid, TP_ADJ(new), &new->tid);
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287 |
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288 | __release_ptc();
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289 |
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290 | if (do_sched) {
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291 | __restore_sigs(new->sigmask);
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292 | }
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293 |
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294 | if (ret < 0) {
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295 | a_dec(&libc.threads_minus_1);
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296 | if (map) __munmap(map, size);
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297 | return EAGAIN;
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298 | }
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299 |
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300 | if (do_sched) {
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301 | ret = __syscall(SYS_sched_setscheduler, new->tid,
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302 | attr._a_policy, &attr._a_prio);
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303 | a_store(new->startlock, ret<0 ? 2 : 3);
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304 | __wake(new->startlock, 1, 1);
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305 | if (ret < 0) return -ret;
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306 | }
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307 |
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308 | *res = new;
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309 | return 0;
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310 | fail:
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311 | __release_ptc();
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312 | return EAGAIN;
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313 | }
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314 |
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315 | weak_alias(__pthread_exit, pthread_exit);
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316 | weak_alias(__pthread_create, pthread_create);
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