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1 /* Mudflap: narrow-pointer bounds-checking by tree rewriting.
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2 Copyright (C) 2002, 2003, 2004, 2005, 2009
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3 Free Software Foundation, Inc.
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4 Contributed by Frank Ch. Eigler <fche@redhat.com>
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5 and Graydon Hoare <graydon@redhat.com>
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6
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7 This file is part of GCC.
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8
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9 GCC is free software; you can redistribute it and/or modify it under
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10 the terms of the GNU General Public License as published by the Free
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11 Software Foundation; either version 3, or (at your option) any later
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12 version.
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13
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14 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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15 WARRANTY; without even the implied warranty of MERCHANTABILITY or
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16 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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17 for more details.
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18
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19 Under Section 7 of GPL version 3, you are granted additional
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20 permissions described in the GCC Runtime Library Exception, version
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21 3.1, as published by the Free Software Foundation.
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22
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23 You should have received a copy of the GNU General Public License and
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24 a copy of the GCC Runtime Library Exception along with this program;
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25 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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26 <http://www.gnu.org/licenses/>. */
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27
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28
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29 #include "config.h"
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30
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31 #ifndef HAVE_SOCKLEN_T
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32 #define socklen_t int
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33 #endif
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34
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35 /* These attempt to coax various unix flavours to declare all our
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36 needed tidbits in the system headers. */
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37 #if !defined(__FreeBSD__) && !defined(__APPLE__)
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38 #define _POSIX_SOURCE
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39 #endif /* Some BSDs break <sys/socket.h> if this is defined. */
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40 #define _GNU_SOURCE
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41 #define _XOPEN_SOURCE
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42 #define _BSD_TYPES
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43 #define __EXTENSIONS__
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44 #define _ALL_SOURCE
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45 #define _LARGE_FILE_API
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46 #define _XOPEN_SOURCE_EXTENDED 1
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47
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48 #include <string.h>
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49 #include <stdio.h>
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50 #include <stdlib.h>
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51 #include <unistd.h>
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52 #include <assert.h>
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53 #include <errno.h>
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54 #include <stdbool.h>
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55
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56 #include "mf-runtime.h"
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57 #include "mf-impl.h"
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58
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59 #ifdef _MUDFLAP
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60 #error "Do not compile this file with -fmudflap!"
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61 #endif
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62
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63 #ifndef LIBMUDFLAPTH
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64 #error "pthreadstuff is to be included only in libmudflapth"
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65 #endif
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66
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67 /* ??? Why isn't this done once in the header files. */
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68 DECLARE(void *, malloc, size_t sz);
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69 DECLARE(void, free, void *ptr);
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70 DECLARE(int, pthread_create, pthread_t *thr, const pthread_attr_t *attr,
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71 void * (*start) (void *), void *arg);
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72
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73
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74 /* Multithreading support hooks. */
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75
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76
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77 #if !defined(HAVE_TLS) || defined(USE_EMUTLS)
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78 /* We don't have TLS. Ordinarily we could use pthread keys, but since we're
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79 commandeering malloc/free that presents a few problems. The first is that
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80 we'll recurse from __mf_get_state to pthread_setspecific to malloc back to
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81 __mf_get_state during thread startup. This can be solved with clever uses
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82 of a mutex. The second problem is that thread shutdown is indistinguishable
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83 from thread startup, since libpthread is deallocating our state variable.
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84 I've no good solution for this.
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85
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86 Which leaves us to handle this mess by totally by hand. */
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87
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88 /* Yes, we want this prime. If pthread_t is a pointer, it's almost always
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89 page aligned, and if we use a smaller power of 2, this results in "%N"
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90 being the worst possible hash -- all threads hash to zero. */
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91 #define LIBMUDFLAPTH_THREADS_MAX 1021
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92
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93 struct mf_thread_data
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94 {
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95 pthread_t self;
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96 unsigned char used_p;
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97 unsigned char state;
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98 };
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99
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100 static struct mf_thread_data mf_thread_data[LIBMUDFLAPTH_THREADS_MAX];
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101 static pthread_mutex_t mf_thread_data_lock = PTHREAD_MUTEX_INITIALIZER;
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102
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103 #define PTHREAD_HASH(p) ((unsigned long) (p) % LIBMUDFLAPTH_THREADS_MAX)
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104
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105 static struct mf_thread_data *
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106 __mf_find_threadinfo (int alloc)
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107 {
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108 pthread_t self = pthread_self ();
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109 unsigned long hash = PTHREAD_HASH (self);
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110 unsigned long rehash;
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111
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112 #ifdef __alpha__
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113 /* Alpha has the loosest memory ordering rules of all. We need a memory
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114 barrier to flush the reorder buffer before considering a *read* of a
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115 shared variable. Since we're not always taking a lock, we have to do
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116 this by hand. */
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117 __sync_synchronize ();
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118 #endif
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119
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120 rehash = hash;
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121 while (1)
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122 {
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123 if (mf_thread_data[rehash].used_p && mf_thread_data[rehash].self == self)
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124 return &mf_thread_data[rehash];
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125
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126 rehash += 7;
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127 if (rehash >= LIBMUDFLAPTH_THREADS_MAX)
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128 rehash -= LIBMUDFLAPTH_THREADS_MAX;
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129 if (rehash == hash)
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130 break;
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131 }
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132
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133 if (alloc)
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134 {
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135 pthread_mutex_lock (&mf_thread_data_lock);
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136
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137 rehash = hash;
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138 while (1)
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139 {
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140 if (!mf_thread_data[rehash].used_p)
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141 {
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142 mf_thread_data[rehash].self = self;
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143 __sync_synchronize ();
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144 mf_thread_data[rehash].used_p = 1;
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145
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146 pthread_mutex_unlock (&mf_thread_data_lock);
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147 return &mf_thread_data[rehash];
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148 }
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149
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150 rehash += 7;
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151 if (rehash >= LIBMUDFLAPTH_THREADS_MAX)
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152 rehash -= LIBMUDFLAPTH_THREADS_MAX;
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153 if (rehash == hash)
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154 break;
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155 }
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156
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157 pthread_mutex_unlock (&mf_thread_data_lock);
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158 }
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159
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160 return NULL;
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161 }
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162
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163 enum __mf_state_enum
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164 __mf_get_state (void)
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165 {
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166 struct mf_thread_data *data = __mf_find_threadinfo (0);
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167 if (data)
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168 return data->state;
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169
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170 /* If we've never seen this thread before, consider it to be in the
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171 reentrant state. The state gets reset to active for the main thread
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172 in __mf_init, and for child threads in __mf_pthread_spawner.
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173
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174 The trickiest bit here is that the LinuxThreads pthread_manager thread
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175 should *always* be considered to be reentrant, so that none of our
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176 hooks actually do anything. Why? Because that thread isn't a real
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177 thread from the point of view of the thread library, and so lots of
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178 stuff isn't initialized, leading to SEGV very quickly. Even calling
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179 pthread_self is a bit suspect, but it happens to work. */
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180
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181 return reentrant;
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182 }
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183
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184 void
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185 __mf_set_state (enum __mf_state_enum new_state)
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186 {
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187 struct mf_thread_data *data = __mf_find_threadinfo (1);
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188 data->state = new_state;
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189 }
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190 #endif
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191
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192 /* The following two functions are used only with __mf_opts.heur_std_data.
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193 We're interested in recording the location of the thread-local errno
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194 variable.
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195
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196 Note that this doesn't handle TLS references in general; we have no
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197 visibility into __tls_get_data for when that memory is allocated at
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198 runtime. Hopefully we get to see the malloc or mmap operation that
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199 eventually allocates the backing store. */
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200
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201 /* Describe the startup information for a new user thread. */
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202 struct mf_thread_start_info
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203 {
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204 /* The user's thread entry point and argument. */
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205 void * (*user_fn)(void *);
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206 void *user_arg;
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207 };
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208
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209
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210 static void
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211 __mf_pthread_cleanup (void *arg)
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212 {
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213 if (__mf_opts.heur_std_data)
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214 __mf_unregister (&errno, sizeof (errno), __MF_TYPE_GUESS);
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215
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216 #if !defined(HAVE_TLS) || defined(USE_EMUTLS)
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217 struct mf_thread_data *data = __mf_find_threadinfo (0);
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218 if (data)
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219 data->used_p = 0;
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220 #endif
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221 }
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222
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223
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224 static void *
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225 __mf_pthread_spawner (void *arg)
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226 {
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227 void *result = NULL;
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228
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229 __mf_set_state (active);
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230
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231 /* NB: We could use __MF_TYPE_STATIC here, but we guess that the thread
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232 errno is coming out of some dynamically allocated pool that we already
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233 know of as __MF_TYPE_HEAP. */
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234 if (__mf_opts.heur_std_data)
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235 __mf_register (&errno, sizeof (errno), __MF_TYPE_GUESS,
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236 "errno area (thread)");
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237
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238 /* We considered using pthread_key_t objects instead of these
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239 cleanup stacks, but they were less cooperative with the
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240 interposed malloc hooks in libmudflap. */
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241 /* ??? The pthread_key_t problem is solved above... */
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242 pthread_cleanup_push (__mf_pthread_cleanup, NULL);
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243
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244 /* Extract given entry point and argument. */
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245 struct mf_thread_start_info *psi = arg;
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246 void * (*user_fn)(void *) = psi->user_fn;
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247 void *user_arg = psi->user_arg;
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248 CALL_REAL (free, arg);
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249
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250 result = (*user_fn)(user_arg);
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251
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252 pthread_cleanup_pop (1 /* execute */);
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253
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254 return result;
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255 }
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256
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257
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258 #if PIC
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259 /* A special bootstrap variant. */
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260 int
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261 __mf_0fn_pthread_create (pthread_t *thr, const pthread_attr_t *attr,
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262 void * (*start) (void *), void *arg)
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263 {
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264 return -1;
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265 }
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266 #endif
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267
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268
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269 #undef pthread_create
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270 WRAPPER(int, pthread_create, pthread_t *thr, const pthread_attr_t *attr,
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271 void * (*start) (void *), void *arg)
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272 {
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273 struct mf_thread_start_info *si;
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274
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275 TRACE ("pthread_create\n");
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276
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277 /* Fill in startup-control fields. */
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278 si = CALL_REAL (malloc, sizeof (*si));
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279 si->user_fn = start;
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280 si->user_arg = arg;
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281
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282 /* Actually create the thread. */
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283 return CALL_REAL (pthread_create, thr, attr, __mf_pthread_spawner, si);
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284 }
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