1 | /** |
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2 | * @file |
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3 | */ |
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4 | |
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5 | /* |
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6 | * Copyright (c) 2012 Chris Johns (chrisj@rtems.org) |
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7 | * Copyright (c) 2017 Gedare Bloom (gedare@rtems.org) |
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8 | * Copyright (c) 2017 Kevin kirspel (kirspkt@gmail.com) |
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9 | * |
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10 | * The license and distribution terms for this file may be |
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11 | * found in the file LICENSE in this distribution or at |
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12 | * http://www.rtems.org/license/LICENSE. |
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13 | */ |
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14 | |
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15 | #if HAVE_CONFIG_H |
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16 | #include "config.h" |
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17 | #endif |
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18 | |
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19 | #include <rtems.h> |
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20 | #include <errno.h> |
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21 | #include <stdlib.h> |
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22 | #include <sys/mman.h> |
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23 | #include <sys/stat.h> |
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24 | #include <unistd.h> |
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25 | |
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26 | #include "rtems/libio_.h" |
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27 | |
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28 | #include <rtems/posix/mmanimpl.h> |
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29 | #include <rtems/posix/shmimpl.h> |
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30 | |
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31 | #define RTEMS_MUTEX_ATTRIBS \ |
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32 | (RTEMS_PRIORITY | RTEMS_SIMPLE_BINARY_SEMAPHORE | \ |
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33 | RTEMS_NO_INHERIT_PRIORITY | RTEMS_NO_PRIORITY_CEILING | RTEMS_LOCAL) |
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34 | |
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35 | /** |
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36 | * Mmap chain of mappings. |
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37 | */ |
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38 | rtems_chain_control mmap_mappings; |
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39 | |
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40 | /** |
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41 | * The id of the MMAP lock. |
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42 | */ |
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43 | static rtems_id mmap_mappings_lock; |
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44 | |
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45 | /** |
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46 | * Create the lock. |
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47 | */ |
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48 | static |
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49 | bool mmap_mappings_lock_create( |
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50 | void |
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51 | ) |
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52 | { |
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53 | /* |
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54 | * Lock the mapping table. We only create a lock if a call is made. First we |
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55 | * test if a mapping lock is present. If one is present we lock it. If not |
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56 | * the libio lock is locked and we then test the mapping lock again. If not |
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57 | * present we create the mapping lock then release libio lock. |
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58 | */ |
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59 | /* FIXME: double-checked locking anti-pattern. */ |
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60 | if ( mmap_mappings_lock == 0 ) { |
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61 | rtems_status_code sc = RTEMS_SUCCESSFUL; |
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62 | rtems_chain_initialize_empty( &mmap_mappings ); |
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63 | rtems_semaphore_obtain( rtems_libio_semaphore, |
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64 | RTEMS_WAIT, RTEMS_NO_TIMEOUT ); |
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65 | /* FIXME: account for semaphore in confdefs, or maybe just use the |
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66 | * rtems_libio_semaphore? */ |
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67 | if ( mmap_mappings_lock == 0 ) |
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68 | sc = rtems_semaphore_create( rtems_build_name( 'M', 'M', 'A', 'P' ), |
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69 | 1, |
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70 | RTEMS_MUTEX_ATTRIBS, |
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71 | RTEMS_NO_PRIORITY, |
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72 | &mmap_mappings_lock ); |
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73 | rtems_semaphore_release( rtems_libio_semaphore ); |
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74 | if ( sc != RTEMS_SUCCESSFUL ) { |
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75 | errno = EINVAL; |
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76 | return false; |
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77 | } |
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78 | } |
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79 | return true; |
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80 | } |
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81 | |
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82 | bool mmap_mappings_lock_obtain( |
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83 | void |
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84 | ) |
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85 | { |
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86 | if ( mmap_mappings_lock_create( ) ) { |
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87 | rtems_status_code sc; |
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88 | sc = rtems_semaphore_obtain( mmap_mappings_lock, |
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89 | RTEMS_WAIT, RTEMS_NO_TIMEOUT ); |
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90 | if ( sc != RTEMS_SUCCESSFUL ) { |
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91 | errno = EINVAL; |
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92 | return false; |
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93 | } |
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94 | } |
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95 | return true; |
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96 | } |
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97 | |
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98 | bool mmap_mappings_lock_release( |
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99 | void |
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100 | ) |
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101 | { |
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102 | rtems_status_code sc; |
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103 | sc = rtems_semaphore_release( mmap_mappings_lock ); |
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104 | if (( sc != RTEMS_SUCCESSFUL ) && ( errno == 0 )) { |
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105 | errno = EINVAL; |
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106 | return false; |
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107 | } |
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108 | return true; |
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109 | } |
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110 | |
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111 | void *mmap( |
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112 | void *addr, size_t len, int prot, int flags, int fildes, off_t off |
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113 | ) |
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114 | { |
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115 | struct stat sb; |
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116 | mmap_mapping *mapping; |
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117 | mmap_mapping *current_mapping; |
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118 | ssize_t r; |
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119 | rtems_libio_t *iop; |
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120 | bool map_fixed; |
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121 | bool map_anonymous; |
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122 | bool map_shared; |
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123 | bool map_private; |
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124 | int err; |
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125 | |
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126 | map_fixed = (flags & MAP_FIXED) == MAP_FIXED; |
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127 | map_anonymous = (flags & MAP_ANON) == MAP_ANON; |
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128 | map_shared = (flags & MAP_SHARED) == MAP_SHARED; |
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129 | map_private = (flags & MAP_PRIVATE) == MAP_PRIVATE; |
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130 | |
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131 | /* Clear errno. */ |
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132 | errno = 0; |
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133 | iop = NULL; |
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134 | |
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135 | if ( len == 0 ) { |
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136 | errno = EINVAL; |
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137 | return MAP_FAILED; |
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138 | } |
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139 | |
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140 | /* |
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141 | * We can provide read, write and execute because the memory in RTEMS does |
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142 | * not normally have protections but we cannot hide access to memory. |
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143 | */ |
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144 | if ( prot == PROT_NONE ) { |
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145 | errno = ENOTSUP; |
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146 | return MAP_FAILED; |
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147 | } |
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148 | |
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149 | /* |
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150 | * We can not normally provide restriction of write access. Reject any |
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151 | * attempt to map without write permission, since we are not able to |
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152 | * prevent a write from succeeding. |
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153 | */ |
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154 | if ( PROT_WRITE != (prot & PROT_WRITE) ) { |
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155 | errno = ENOTSUP; |
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156 | return MAP_FAILED; |
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157 | } |
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158 | |
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159 | /* |
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160 | * Anonymous mappings must have file descriptor set to -1 and the offset |
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161 | * set to 0. Shared mappings are not supported with Anonymous mappings at |
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162 | * this time |
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163 | */ |
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164 | if ( map_anonymous && (fildes != -1 || off != 0 || map_shared) ) { |
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165 | errno = EINVAL; |
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166 | return MAP_FAILED; |
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167 | } |
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168 | |
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169 | /* |
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170 | * If MAP_ANON is declared without MAP_PRIVATE or MAP_SHARED, |
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171 | * force MAP_PRIVATE |
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172 | */ |
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173 | if ( map_anonymous && !map_private && !map_shared ) { |
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174 | flags |= MAP_PRIVATE; |
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175 | map_private = true; |
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176 | } |
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177 | |
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178 | /* Check for supported flags */ |
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179 | if ((flags & ~(MAP_SHARED | MAP_PRIVATE | MAP_FIXED | MAP_ANON)) != 0) { |
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180 | errno = EINVAL; |
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181 | return MAP_FAILED; |
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182 | } |
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183 | |
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184 | /* Either MAP_SHARED or MAP_PRIVATE must be defined, but not both */ |
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185 | if ( map_shared ) { |
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186 | if ( map_private ) { |
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187 | errno = EINVAL; |
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188 | return MAP_FAILED; |
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189 | } |
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190 | } else if ( !map_private ) { |
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191 | errno = EINVAL; |
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192 | return MAP_FAILED; |
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193 | } |
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194 | |
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195 | /* Check for illegal addresses. Watch out for address wrap. */ |
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196 | if ( map_fixed ) { |
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197 | if ((uintptr_t)addr & PAGE_MASK) { |
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198 | errno = EINVAL; |
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199 | return MAP_FAILED; |
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200 | } |
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201 | if ( addr == NULL ) { |
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202 | errno = EINVAL; |
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203 | return MAP_FAILED; |
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204 | } |
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205 | if (addr + len < addr) { |
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206 | errno = EINVAL; |
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207 | return MAP_FAILED; |
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208 | } |
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209 | } |
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210 | |
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211 | if ( !map_anonymous ) { |
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212 | /* |
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213 | * Get a stat of the file to get the dev + inode number and to make sure the |
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214 | * fd is ok. The normal libio calls cannot be used because we need to return |
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215 | * MAP_FAILED on error and they return -1 directly without coming back to |
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216 | * here. |
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217 | */ |
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218 | if ( fstat( fildes, &sb ) < 0 ) { |
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219 | errno = EBADF; |
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220 | return MAP_FAILED; |
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221 | } |
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222 | |
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223 | /* fstat ensures we have a good file descriptor. Hold on to iop. */ |
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224 | iop = rtems_libio_iop( fildes ); |
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225 | |
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226 | /* Check the type of file we have and make sure it is supported. */ |
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227 | if ( S_ISDIR( sb.st_mode ) || S_ISLNK( sb.st_mode )) { |
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228 | errno = ENODEV; |
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229 | return MAP_FAILED; |
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230 | } |
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231 | |
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232 | /* Check to see if the mapping is valid for a regular file. */ |
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233 | if ( S_ISREG( sb.st_mode ) |
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234 | /* FIXME: Should this be using strict inequality (>) comparisons? It would |
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235 | * be valid to map a region exactly equal to the st_size, e.g. see below. */ |
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236 | && (( off >= sb.st_size ) || (( off + len ) >= sb.st_size ))) { |
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237 | errno = EOVERFLOW; |
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238 | return MAP_FAILED; |
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239 | } |
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240 | |
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241 | /* Check to see if the mapping is valid for other file/object types. */ |
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242 | if ( !S_ISCHR( sb.st_mode ) && sb.st_size < off + len ) { |
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243 | errno = ENXIO; |
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244 | return MAP_FAILED; |
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245 | } |
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246 | |
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247 | /* Do not seek on character devices, pipes, sockets, or memory objects. */ |
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248 | if ( S_ISREG( sb.st_mode ) || S_ISBLK( sb.st_mode ) ) { |
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249 | if ( lseek( fildes, off, SEEK_SET ) < 0 ) { |
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250 | return MAP_FAILED; |
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251 | } |
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252 | } |
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253 | |
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254 | /* cdevs do not provide private mappings of any kind. */ |
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255 | if ( S_ISCHR( sb.st_mode ) && map_private ) { |
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256 | errno = EINVAL; |
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257 | return MAP_FAILED; |
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258 | } |
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259 | } |
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260 | |
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261 | /* Create the mapping */ |
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262 | mapping = malloc( sizeof( mmap_mapping )); |
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263 | if ( !mapping ) { |
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264 | errno = ENOMEM; |
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265 | return MAP_FAILED; |
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266 | } |
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267 | memset( mapping, 0, sizeof( mmap_mapping )); |
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268 | mapping->len = len; |
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269 | mapping->flags = flags; |
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270 | mapping->iop = iop; |
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271 | |
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272 | if ( !map_anonymous ) { |
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273 | /* |
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274 | * HACK: We should have a better generic way to distinguish between |
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275 | * shm objects and other mmap'd files. We need to know at munmap time |
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276 | * if the mapping is to a shared memory object in order to refcnt shms. |
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277 | * We could do this by providing mmap in the file operations if needed. |
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278 | */ |
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279 | if ( S_ISREG( sb.st_mode ) || S_ISBLK( sb.st_mode ) || |
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280 | S_ISCHR( sb.st_mode ) || S_ISFIFO( sb.st_mode ) || |
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281 | S_ISSOCK( sb.st_mode ) ) { |
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282 | mapping->is_shared_shm = false; |
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283 | } else { |
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284 | mapping->is_shared_shm = true; |
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285 | } |
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286 | } else { |
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287 | mapping->is_shared_shm = false; |
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288 | } |
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289 | |
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290 | if ( map_fixed ) { |
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291 | mapping->addr = addr; |
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292 | } else if ( map_private ) { |
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293 | /* private mappings of shared memory do not need special treatment. */ |
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294 | mapping->is_shared_shm = false; |
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295 | posix_memalign( &mapping->addr, PAGE_SIZE, len ); |
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296 | if ( !mapping->addr ) { |
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297 | free( mapping ); |
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298 | errno = ENOMEM; |
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299 | return MAP_FAILED; |
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300 | } |
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301 | } |
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302 | |
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303 | /* MAP_FIXED is not supported for shared memory objects with MAP_SHARED. */ |
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304 | if ( map_fixed && mapping->is_shared_shm ) { |
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305 | free( mapping ); |
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306 | errno = ENOTSUP; |
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307 | return MAP_FAILED; |
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308 | } |
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309 | |
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310 | /* Lock access to mmap_mappings. Sets errno on failure. */ |
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311 | if ( !mmap_mappings_lock_obtain( ) ) |
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312 | return MAP_FAILED; |
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313 | |
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314 | if ( map_fixed ) { |
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315 | rtems_chain_node* node = rtems_chain_first (&mmap_mappings); |
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316 | while ( !rtems_chain_is_tail( &mmap_mappings, node )) { |
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317 | /* |
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318 | * If the map is fixed see if this address is already mapped. At this |
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319 | * point in time if there is an overlap in the mappings we return an |
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320 | * error. POSIX allows us to also return successfully by unmapping |
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321 | * the overlapping prior mappings. |
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322 | */ |
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323 | current_mapping = (mmap_mapping*) node; |
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324 | if ( ( addr >= current_mapping->addr ) && |
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325 | ( addr < ( current_mapping->addr + current_mapping->len )) ) { |
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326 | free( mapping ); |
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327 | mmap_mappings_lock_release( ); |
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328 | errno = ENXIO; |
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329 | return MAP_FAILED; |
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330 | } |
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331 | node = rtems_chain_next( node ); |
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332 | } |
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333 | } |
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334 | |
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335 | /* Populate the data */ |
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336 | if ( map_private ) { |
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337 | if ( !map_anonymous ) { |
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338 | /* |
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339 | * Use read() for private mappings. This updates atime as needed. |
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340 | * Changes to the underlying object will NOT be reflected in the mapping. |
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341 | * The underlying object can be removed while the mapping exists. |
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342 | */ |
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343 | r = read( fildes, mapping->addr, len ); |
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344 | |
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345 | if ( r != len ) { |
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346 | mmap_mappings_lock_release( ); |
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347 | if ( !map_fixed ) { |
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348 | free( mapping->addr ); |
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349 | } |
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350 | free( mapping ); |
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351 | errno = ENXIO; |
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352 | return MAP_FAILED; |
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353 | } |
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354 | } else if ( !map_fixed ) { |
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355 | memset( mapping->addr, 0, len ); |
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356 | } |
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357 | } else if ( map_shared ) { |
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358 | err = (*iop->pathinfo.handlers->mmap_h)( |
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359 | iop, &mapping->addr, len, prot, off ); |
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360 | if ( err != 0 ) { |
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361 | mmap_mappings_lock_release( ); |
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362 | free( mapping ); |
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363 | return MAP_FAILED; |
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364 | } |
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365 | } |
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366 | |
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367 | if ( iop != NULL ) { |
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368 | /* add an extra reference to the file associated with fildes that |
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369 | * is not removed by a subsequent close(). This reference shall be removed |
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370 | * when there are no more mappings to the file. */ |
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371 | rtems_libio_increment_mapping_refcnt(iop); |
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372 | } |
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373 | |
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374 | rtems_chain_append_unprotected( &mmap_mappings, &mapping->node ); |
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375 | |
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376 | mmap_mappings_lock_release( ); |
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377 | |
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378 | return mapping->addr; |
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379 | } |
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