1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 2 <html xmlns="http://www.w3.org/1999/xhtml"> 3 <head> 4 <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> 5 <link href="style.css" rel="stylesheet" type="text/css" /> 6 <title>Debug Sybmols on Mac OS X</title> 7 </head> 8 9 <body> 10 <div class="www_title"> 11 The <strong>LLDB</strong> Debugger 12 </div> 13 14 <div id="container"> 15 <div id="content"> 16 17 <!--#include virtual="sidebar.incl"--> 18 19 <div id="middle"> 20 <div class="post"> 21 <h1 class="postheader">Debug Symbols on MacOSX</h1> 22 <div class="postcontent"> 23 <p>On MacOSX, debug symbols are often in stand alone bundles called <b>dSYM</b> files. 24 These are bundles that contain DWARF debug information and other resources related to 25 builds and debug info.</p> 26 <p>The DebugSymbols.framework framework helps locate dSYM files when given a UUID. It can 27 locate the symbols using a variety of methods:</p> 28 <ul> 29 <li>Spotlight</li> 30 <li>Explicit search paths</li> 31 <li>Implicit search paths</li> 32 <li>File mapped UUID paths</li> 33 <li>Running one or more shell scripts</li> 34 </ul> 35 <p>DebugSymbols.framework also has global defaults that can be modified to allow 36 all of the debug tools (lldb, gdb, sample, CoreSymbolication.framework) to easily 37 find important debug symbols. The domain for the DebugSymbols.framework defaults 38 is <b>com.apple.DebugSymbols</b>, and the defaults can be read, written or modified 39 using the <b>defaults</b> shell command: 40 <code><pre><tt><b>% defaults read com.apple.DebugSymbols 41 % defaults write com.apple.DebugSymbols KEY ... 42 % defaults delete com.apple.DebugSymbols KEY</b> 43 </tt></pre></code> 44 45 <p>The following is a list of the defaults key value 46 setting pairs that can be used to enhance symbol location:</p> 47 <table class="stats" width="620" cellspacing="0"> 48 <tr> 49 <td class="hed" width="20%">Defaults Key</td> 50 <td class="hed" width="70%">Description</td> 51 </tr> 52 53 <tr> 54 <td class="content"> 55 <b>DBGFileMappedPaths</b> 56 </td> 57 <td class="content"> 58 This default can be specified as a single string, or an array of strings. 59 Each string represents a directory that contains file mapped UUID values 60 that point to dSYM files. See the "File Mapped UUID Directories" section 61 below for more details. Whenever DebugSymbols.framework is asked to lookup 62 a dSYM file, it will first look in any file mapped UUID directories 63 for a quick match. 64 </td> 65 </tr> 66 <td class="content" colspan="2"> 67 <code><pre><tt><b>% defaults write com.apple.DebugSymbols DBGFileMappedPaths -string /path/to/uuidmap1</b> 68 <b>% defaults write com.apple.DebugSymbols DBGFileMappedPaths -array /path/to/uuidmap1 69 /path/to/uuidmap2</b> 70 </tt></pre></code> 71 </tr> 72 <tr> 73 <td class="content"> 74 <b>DBGShellCommands</b> 75 </td> 76 <td class="content"> 77 This default can be specified as a single string, or an array of strings. 78 Specifies a shell script that will get run in order to find the dSYM. 79 The shell script will be run given a single UUID value as the shell 80 command arguments and the shell command is expected to return a property 81 list. See the property list format defined below. 82 </td> 83 </tr> 84 <td class="content" colspan="2"> 85 <code><pre><tt><b>% defaults write com.apple.DebugSymbols DBGShellCommands -string /path/to/script1</b> 86 <b>% defaults write com.apple.DebugSymbols DBGShellCommands -array /path/to/script1 87 /path/to/script2</b> 88 </tt></pre></code> 89 </td> 90 </tr> 91 <tr> 92 <td class="content"> 93 <b>DBGSpotlightPaths</b> 94 </td> 95 <td class="content"> 96 Specifies the directories to limit spotlight searches to as a string or array of strings. When any 97 other defaults are supplied to <b>com.apple.DebugSymbols</b>, spotlight 98 searches will be disabled unless this default is set to an empty array: 99 </td> 100 </tr> 101 <td class="content" colspan="2"> 102 <code><pre><tt><font color="green"># Specify an empty array to keep Spotlight searches enabled in all locations</font> 103 <b>% defaults write com.apple.DebugSymbols DBGSpotlightPaths -array</b> 104 105 <font color="green"># Specify an array of paths to limit spotlight searches to certain directories</font> 106 <b>% defaults write com.apple.DebugSymbols DBGSpotlightPaths -array /path/dir1 /path/dir2</b> 107 </tt></pre></code> 108 </td> 109 </tr> 110 </table> 111 </div> 112 <div class="postfooter"></div> 113 </div> 114 <div class="post"> 115 <h1 class="postheader">Shell Script Property List Format</h1> 116 <div class="postcontent"> 117 <p>Shell scripts that are specified with the <b>DBGShellCommands</b> defaults key 118 will be run in the order in which they are specified until a match is found. 119 The shell script will be invoked with a single UUID string value like 120 "23516BE4-29BE-350C-91C9-F36E7999F0F1". The shell script must respond with a 121 property list being written to STDOUT. 122 The property list returned must contain UUID string values as the root key values, with 123 a dictionary for each UUID. The dictionaries can contain one or more of the following keys: 124 125 <table class="stats" width="620" cellspacing="0"> 126 <tr> 127 <td class="hed" width="20%">Key</td> 128 <td class="hed" width="70%">Description</td> 129 </tr> 130 <tr> 131 <td class="content"> 132 <b>DBGArchitecture</b> 133 </td> 134 <td class="content">A textual architecture or target triple like "x86_64", "i386", or "x86_64-apple-macosx". 135 </td> 136 </tr> 137 <tr> 138 <td class="content"> 139 <b>DBGBuildSourcePath</b> 140 </td> 141 <td class="content">A path prefix that was used when building the dSYM file. The debug information will 142 contain paths with this prefix. 143 </td> 144 </tr> 145 <tr> 146 <td class="content"> 147 <b>DBGSourcePath</b> 148 </td> 149 <td class="content">A path prefix for where the sources exist after the build has completed. Often when 150 building projects, build machines will host the sources in a temporary directory while building, then 151 move the sources to another location for archiving. If the paths in the debug info don't match where 152 the sources are currently hosted, then specifying this path along with the <b>DBGBuildSourcePath</b> 153 will help the developer tools always show you sources when debugging or symbolicating. 154 </td> 155 </tr> 156 <tr> 157 <td class="content"> 158 <b>DBGDSYMPath</b> 159 </td> 160 <td class="content">A path to the dSYM mach-o file inside the dSYM bundle. 161 </td> 162 </tr> 163 <tr> 164 <td class="content"> 165 <b>DBGSymbolRichExecutable</b> 166 </td> 167 <td class="content">A path to the symbol rich executable. Binaries are often stripped after 168 being built and packaged into a release. If your build systems saves an unstripped executable 169 a path to this executable can be provided. 170 </td> 171 </tr> 172 <tr> 173 <td class="content"> 174 <b>DBGError</b> 175 </td> 176 <td class="content">If a binary can not be located for the supplied UUID, a user readable error 177 can be returned. 178 </td> 179 </tr> 180 </table> 181 182 <p>Below is a sample shell script output for a binary that contains two architectures: 183 <code><pre><tt> 184 <?xml version="1.0" encoding="UTF-8"?> 185 <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> 186 <plist version="1.0"> 187 <dict> 188 <key>23516BE4-29BE-350C-91C9-F36E7999F0F1</key> 189 <dict> 190 <key>DBGArchitecture</key> 191 <string>i386</string> 192 <key>DBGBuildSourcePath</key> 193 <string>/path/to/build/sources</string> 194 <key>DBGSourcePath</key> 195 <string>/path/to/actual/sources</string> 196 <key>DBGDSYMPath</key> 197 <string>/path/to/foo.dSYM/Contents/Resources/DWARF/foo</string> 198 <key>DBGSymbolRichExecutable</key> 199 <string>/path/to/unstripped/exectuable</string> 200 </dict> 201 <key>A40597AA-5529-3337-8C09-D8A014EB1578</key> 202 <dict> 203 <key>DBGArchitecture</key> 204 <string>x86_64</string> 205 <key>DBGBuildSourcePath</key> 206 <string>/path/to/build/sources</string> 207 <key>DBGSourcePath</key> 208 <string>/path/to/actual/sources</string> 209 <key>DBGDSYMPath</key> 210 <string>/path/to/foo.dSYM/Contents/Resources/DWARF/foo</string> 211 <key>DBGSymbolRichExecutable</key> 212 <string>/path/to/unstripped/exectuable</string> 213 </dict> 214 </dict> 215 </plist> 216 </tt></pre></code> 217 218 <p>There is no timeout imposed on a shell script when is it asked to locate a dSYM file, so be careful to not make a shell 219 script that has high latency or takes a long time to download unless this 220 is really what you want. This can slow down debug sessions in LLDB and GDB, symbolication 221 with CoreSymbolication or Report Crash, with no visible feedback to the user. You can 222 quickly return a plist with a single <b>DBGError</b> key that indicates a timeout 223 has been reached. You might also want to exec new processes to do the downloads so 224 that if you return an error that indicates a timeout, your download can still proceed 225 after your shell script has exited so subsequent debug sessions can use the cached files. 226 It is also important to track when a current download is in progress in case you get multiple requests for the same UUID so 227 that you don't end up downloading the same file simultaneously. Also you will want 228 to verify the download was successful and then and only then place the file into the 229 cache for tools that will cache files locally. 230 </div> 231 <div class="postfooter"></div> 232 </div> 233 <div class="post"> 234 <h1 class="postheader">Embedding UUID property lists inside the dSYM bundles</h1> 235 <div class="postcontent"> 236 <p>Since dSYM files are bundles, you can also place UUID info plists files inside 237 your dSYM bundles in the <b>Contents/Resources</b> directory. One of the main 238 reasons to create the UUID plists inside the dSYM bundles 239 is that it will help LLDB and other developer tools show you source. LLDB currently 240 knows how to check for these plist files so it can automatically remap the source 241 location information in the debug info. 242 243 <p>If we take the two UUID values from the returns plist above, we can split 244 them out and save then in the dSYM bundle: 245 246 <code><pre><tt><b>% ls /path/to/foo.dSYM/Contents/Resources</b> 247 23516BE4-29BE-350C-91C9-F36E7999F0F1.plist 248 A40597AA-5529-3337-8C09-D8A014EB1578.plist 249 250 <b>% cat /path/to/foo.dSYM/Contents/Resources/23516BE4-29BE-350C-91C9-F36E7999F0F1.plist</b> 251 <?xml version="1.0" encoding="UTF-8"?> 252 <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> 253 <plist version="1.0"> 254 <dict> 255 <key>DBGArchitecture</key> 256 <string>i386</string> 257 <key>DBGBuildSourcePath</key> 258 <string>/path/to/build/sources</string> 259 <key>DBGSourcePath</key> 260 <string>/path/to/actual/sources</string> 261 <key>DBGDSYMPath</key> 262 <string>/path/to/foo.dSYM/Contents/Resources/DWARF/foo</string> 263 <key>DBGSymbolRichExecutable</key> 264 <string>/path/to/unstripped/exectuable</string> 265 </dict> 266 </plist> 267 </tt></pre></code> 268 269 <p>Note that the output is very close to what is needed by shell script output, 270 so making the results of your shell script will be very easy to create by 271 combining two plists into a single one where you take the UUID and use it a 272 string key, and the value is the contents of the plist. 273 274 275 </div> 276 <div class="postfooter"></div> 277 </div> 278 <div class="post"> 279 <h1 class="postheader">File Mapped UUID Directories</h1> 280 <div class="postcontent"> 281 <p>File Mapped directories can be used for efficient dSYM file lookups for 282 local or remote dSYM files. The UUID is broken up by splitting the first 283 20 hex digits into 4 character chunks, and a directory is created for each 284 chunk, and each subsequent directory is created inside the previous one. 285 A symlink is then created whose name is the last 12 hex digits in the deepest 286 directory. The symlinks value is a full path to the mach-o files inside the 287 dSYM bundle which contains the DWARF. Whenever DebugSymbols.framework is asked 288 to lookup a dSYM file, it will first look in any file mapped UUID directories 289 for a quick match if the defaults are appropriately set. 290 291 <p>For example, if we take the sample UUID plist inforamtion from above, we 292 can create a File Mapped UUID directory cache in <b>~/Library/SymbolCache/dsyms/uuids</b>. 293 We can easily see how things are laid out: 294 295 <code><pre><tt><b>% find ~/Library/SymbolCache/dsyms/uuids -type l</b> 296 ~/Library/SymbolCache/dsyms/uuids/2351/6BE4/29BE/350C/91C9/F36E7999F0F1 297 ~/Library/SymbolCache/dsyms/uuids/A405/97AA/5529/3337/8C09/D8A014EB1578 298 </tt></pre></code> 299 300 <p>The last entries in these file mapped directories are symlinks to the actual dsym mach file in the dsym bundle: 301 302 <code><pre><tt><b>% ls -lAF ~/Library/SymbolCache/dsyms/uuids/2351/6BE4/29BE/350C/91C9/F36E7999F0F1</b> 303 ~/Library/SymbolCache/dsyms/uuids/2351/6BE4/29BE/350C/91C9/F36E7999F0F1@ -> ../../../../../../dsyms/foo.dSYM/Contents/Resources/DWARF/foo 304 </tt></pre></code> 305 <p>Then you can also tell DebugSymbols to check this UUID file map cache using: 306 307 <code><pre><tt><b>% defaults write com.apple.DebugSymbols DBGFileMappedPaths ~/Library/SymbolCache/dsyms/uuids</b> 308 </tt></pre></code> 309 310 311 </div> 312 <div class="postfooter"></div> 313 </div> 314 <div class="post"> 315 <h1 class="postheader">dSYM Locating Shell Script Tips</h1> 316 <div class="postcontent"> 317 318 <p>One possible implementation of a dSYM finding shell script is to have the script 319 download and cache files locally in a known location. Then create a UUID map 320 for each UUID value that was found in a local UUID File Map cache so the next query for the dSYM 321 file will be able to use the cached version. So the shell script is used to 322 initially download and cache the file, and subsequent accesses will use the 323 cache and avoid calling the shell script. 324 325 <p>Then the defaults for DebugSymbols.framework will entail enabling your shell script, 326 enabling the file mapped path setting so that already downloaded dSYMS fill quickly 327 be found without needing to run the shell script every time, and also leaving spotlight enabled 328 so that other normal dSYM files are still found: 329 330 <code><pre><tt><b>% defaults write com.apple.DebugSymbols DBGShellCommands /path/to/shellscript 331 % defaults write com.apple.DebugSymbols DBGFileMappedPaths ~/Library/SymbolCache/dsyms/uuids 332 % defaults write com.apple.DebugSymbols DBGSpotlightPaths -array</b> 333 </tt></pre></code> 334 335 Hopefully this helps explain how DebugSymbols.framework can help any company 336 implement a smart symbol finding and caching with minimal overhead. 337 </p> 338 </div> 339 <div class="postfooter"></div> 340 </div> 341 </div> 342 </div> 343 </div> 344 </body> 345 </html>
