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 <string.h> |
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23 | #include <sys/mman.h> |
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24 | #include <sys/stat.h> |
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25 | #include <unistd.h> |
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26 | |
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27 | #include "rtems/libio_.h" |
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28 | |
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29 | #include <rtems/posix/mmanimpl.h> |
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30 | #include <rtems/posix/shmimpl.h> |
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31 | |
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32 | |
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33 | /** |
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34 | * mmap chain of mappings. |
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35 | */ |
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36 | CHAIN_DEFINE_EMPTY( mmap_mappings ); |
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37 | |
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38 | void *mmap( |
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39 | void *addr, size_t len, int prot, int flags, int fildes, off_t off |
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40 | ) |
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41 | { |
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42 | struct stat sb; |
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43 | mmap_mapping *mapping; |
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44 | mmap_mapping *current_mapping; |
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45 | ssize_t r; |
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46 | rtems_libio_t *iop; |
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47 | bool map_fixed; |
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48 | bool map_anonymous; |
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49 | bool map_shared; |
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50 | bool map_private; |
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51 | bool is_shared_shm; |
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52 | int err; |
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53 | |
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54 | map_fixed = (flags & MAP_FIXED) == MAP_FIXED; |
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55 | map_anonymous = (flags & MAP_ANON) == MAP_ANON; |
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56 | map_shared = (flags & MAP_SHARED) == MAP_SHARED; |
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57 | map_private = (flags & MAP_PRIVATE) == MAP_PRIVATE; |
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58 | |
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59 | /* Clear errno. */ |
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60 | errno = 0; |
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61 | iop = NULL; |
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62 | |
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63 | if ( len == 0 ) { |
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64 | errno = EINVAL; |
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65 | return MAP_FAILED; |
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66 | } |
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67 | |
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68 | /* |
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69 | * We can provide read, write and execute because the memory in RTEMS does |
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70 | * not normally have protections but we cannot hide access to memory. |
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71 | */ |
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72 | if ( prot == PROT_NONE ) { |
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73 | errno = ENOTSUP; |
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74 | return MAP_FAILED; |
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75 | } |
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76 | |
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77 | /* |
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78 | * We can not normally provide restriction of write access. Reject any |
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79 | * attempt to map without write permission, since we are not able to |
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80 | * prevent a write from succeeding. |
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81 | */ |
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82 | if ( PROT_WRITE != (prot & PROT_WRITE) ) { |
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83 | errno = ENOTSUP; |
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84 | return MAP_FAILED; |
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85 | } |
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86 | |
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87 | /* |
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88 | * Anonymous mappings must have file descriptor set to -1 and the offset |
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89 | * set to 0. Shared mappings are not supported with Anonymous mappings at |
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90 | * this time |
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91 | */ |
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92 | if ( map_anonymous && (fildes != -1 || off != 0 || map_shared) ) { |
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93 | errno = EINVAL; |
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94 | return MAP_FAILED; |
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95 | } |
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96 | |
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97 | /* |
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98 | * If MAP_ANON is declared without MAP_PRIVATE or MAP_SHARED, |
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99 | * force MAP_PRIVATE |
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100 | */ |
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101 | if ( map_anonymous && !map_private && !map_shared ) { |
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102 | flags |= MAP_PRIVATE; |
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103 | map_private = true; |
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104 | } |
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105 | |
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106 | /* Check for supported flags */ |
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107 | if ((flags & ~(MAP_SHARED | MAP_PRIVATE | MAP_FIXED | MAP_ANON)) != 0) { |
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108 | errno = EINVAL; |
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109 | return MAP_FAILED; |
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110 | } |
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111 | |
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112 | /* Either MAP_SHARED or MAP_PRIVATE must be defined, but not both */ |
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113 | if ( map_shared ) { |
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114 | if ( map_private ) { |
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115 | errno = EINVAL; |
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116 | return MAP_FAILED; |
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117 | } |
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118 | } else if ( !map_private ) { |
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119 | errno = EINVAL; |
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120 | return MAP_FAILED; |
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121 | } |
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122 | |
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123 | /* Check for illegal addresses. Watch out for address wrap. */ |
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124 | if ( map_fixed ) { |
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125 | if ((uintptr_t)addr & PAGE_MASK) { |
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126 | errno = EINVAL; |
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127 | return MAP_FAILED; |
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128 | } |
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129 | if ( addr == NULL ) { |
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130 | errno = EINVAL; |
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131 | return MAP_FAILED; |
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132 | } |
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133 | if (addr + len < addr) { |
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134 | errno = EINVAL; |
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135 | return MAP_FAILED; |
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136 | } |
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137 | } |
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138 | |
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139 | if ( !map_anonymous ) { |
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140 | /* |
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141 | * Get a stat of the file to get the dev + inode number and to make sure the |
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142 | * fd is ok. The normal libio calls cannot be used because we need to return |
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143 | * MAP_FAILED on error and they return -1 directly without coming back to |
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144 | * here. |
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145 | */ |
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146 | if ( fstat( fildes, &sb ) < 0 ) { |
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147 | errno = EBADF; |
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148 | return MAP_FAILED; |
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149 | } |
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150 | |
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151 | /* fstat ensures we have a good file descriptor. Hold on to iop. */ |
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152 | iop = rtems_libio_iop( fildes ); |
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153 | |
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154 | /* Check the type of file we have and make sure it is supported. */ |
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155 | if ( S_ISDIR( sb.st_mode ) || S_ISLNK( sb.st_mode )) { |
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156 | errno = ENODEV; |
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157 | return MAP_FAILED; |
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158 | } |
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159 | |
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160 | /* Check to see if the mapping is valid for a regular file. */ |
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161 | if ( S_ISREG( sb.st_mode ) |
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162 | /* FIXME: Should this be using strict inequality (>) comparisons? It would |
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163 | * be valid to map a region exactly equal to the st_size, e.g. see below. */ |
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164 | && (( off >= sb.st_size ) || (( off + len ) >= sb.st_size ))) { |
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165 | errno = EOVERFLOW; |
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166 | return MAP_FAILED; |
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167 | } |
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168 | |
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169 | /* Check to see if the mapping is valid for other file/object types. */ |
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170 | if ( !S_ISCHR( sb.st_mode ) && sb.st_size < off + len ) { |
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171 | errno = ENXIO; |
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172 | return MAP_FAILED; |
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173 | } |
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174 | |
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175 | /* Do not seek on character devices, pipes, sockets, or memory objects. */ |
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176 | if ( S_ISREG( sb.st_mode ) || S_ISBLK( sb.st_mode ) ) { |
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177 | if ( lseek( fildes, off, SEEK_SET ) < 0 ) { |
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178 | return MAP_FAILED; |
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179 | } |
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180 | } |
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181 | |
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182 | /* cdevs do not provide private mappings of any kind. */ |
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183 | if ( S_ISCHR( sb.st_mode ) && map_private ) { |
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184 | errno = EINVAL; |
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185 | return MAP_FAILED; |
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186 | } |
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187 | } |
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188 | |
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189 | /* Create the mapping */ |
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190 | mapping = malloc( sizeof( mmap_mapping )); |
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191 | if ( !mapping ) { |
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192 | errno = ENOMEM; |
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193 | return MAP_FAILED; |
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194 | } |
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195 | memset( mapping, 0, sizeof( mmap_mapping )); |
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196 | mapping->len = len; |
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197 | mapping->flags = flags; |
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198 | |
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199 | if ( !map_anonymous ) { |
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200 | /* |
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201 | * HACK: We should have a better generic way to distinguish between |
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202 | * shm objects and other mmap'd files. We need to know at munmap time |
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203 | * if the mapping is to a shared memory object in order to refcnt shms. |
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204 | * We could do this by providing mmap in the file operations if needed. |
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205 | */ |
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206 | if ( S_ISREG( sb.st_mode ) || S_ISBLK( sb.st_mode ) || |
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207 | S_ISCHR( sb.st_mode ) || S_ISFIFO( sb.st_mode ) || |
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208 | S_ISSOCK( sb.st_mode ) ) { |
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209 | is_shared_shm = false; |
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210 | } else { |
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211 | is_shared_shm = true; |
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212 | } |
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213 | } else { |
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214 | is_shared_shm = false; |
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215 | } |
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216 | |
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217 | if ( map_fixed ) { |
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218 | mapping->addr = addr; |
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219 | } else if ( map_private ) { |
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220 | /* private mappings of shared memory do not need special treatment. */ |
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221 | is_shared_shm = false; |
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222 | posix_memalign( &mapping->addr, PAGE_SIZE, len ); |
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223 | if ( !mapping->addr ) { |
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224 | free( mapping ); |
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225 | errno = ENOMEM; |
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226 | return MAP_FAILED; |
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227 | } |
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228 | } |
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229 | |
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230 | /* MAP_FIXED is not supported for shared memory objects with MAP_SHARED. */ |
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231 | if ( map_fixed && is_shared_shm ) { |
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232 | free( mapping ); |
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233 | errno = ENOTSUP; |
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234 | return MAP_FAILED; |
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235 | } |
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236 | |
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237 | mmap_mappings_lock_obtain(); |
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238 | |
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239 | if ( map_fixed ) { |
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240 | rtems_chain_node* node = rtems_chain_first (&mmap_mappings); |
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241 | while ( !rtems_chain_is_tail( &mmap_mappings, node )) { |
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242 | /* |
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243 | * If the map is fixed see if this address is already mapped. At this |
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244 | * point in time if there is an overlap in the mappings we return an |
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245 | * error. POSIX allows us to also return successfully by unmapping |
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246 | * the overlapping prior mappings. |
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247 | */ |
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248 | current_mapping = (mmap_mapping*) node; |
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249 | if ( ( addr >= current_mapping->addr ) && |
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250 | ( addr < ( current_mapping->addr + current_mapping->len )) ) { |
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251 | free( mapping ); |
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252 | mmap_mappings_lock_release( ); |
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253 | errno = ENXIO; |
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254 | return MAP_FAILED; |
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255 | } |
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256 | node = rtems_chain_next( node ); |
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257 | } |
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258 | } |
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259 | |
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260 | /* Populate the data */ |
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261 | if ( map_private ) { |
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262 | if ( !map_anonymous ) { |
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263 | /* |
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264 | * Use read() for private mappings. This updates atime as needed. |
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265 | * Changes to the underlying object will NOT be reflected in the mapping. |
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266 | * The underlying object can be removed while the mapping exists. |
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267 | */ |
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268 | r = read( fildes, mapping->addr, len ); |
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269 | |
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270 | if ( r != len ) { |
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271 | mmap_mappings_lock_release( ); |
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272 | if ( !map_fixed ) { |
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273 | free( mapping->addr ); |
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274 | } |
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275 | free( mapping ); |
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276 | errno = ENXIO; |
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277 | return MAP_FAILED; |
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278 | } |
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279 | } else if ( !map_fixed ) { |
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280 | memset( mapping->addr, 0, len ); |
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281 | } |
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282 | } else if ( map_shared ) { |
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283 | if ( is_shared_shm ) { |
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284 | /* FIXME: This use of implementation details is a hack. */ |
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285 | mapping->shm = iop_to_shm( iop ); |
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286 | } |
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287 | |
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288 | err = (*iop->pathinfo.handlers->mmap_h)( |
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289 | iop, &mapping->addr, len, prot, off ); |
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290 | if ( err != 0 ) { |
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291 | mmap_mappings_lock_release( ); |
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292 | free( mapping ); |
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293 | return MAP_FAILED; |
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294 | } |
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295 | } |
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296 | |
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297 | rtems_chain_append_unprotected( &mmap_mappings, &mapping->node ); |
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298 | |
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299 | mmap_mappings_lock_release( ); |
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300 | |
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301 | return mapping->addr; |
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302 | } |
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