build/gdb-add-index

   1 #!/bin/bash
   2 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
   3 # Use of this source code is governed by a BSD-style license that can be
   4 # found in the LICENSE file.
   5 #
   6 # Saves the gdb index for a given binary and its shared library dependencies.
   7 #
   8 # This will run gdb index in parallel on a number of binaries using SIGUSR1
   9 # as the communication mechanism to simulate a semaphore. Because of the
  10 # nature of this technique, using "set -e" is very difficult. The SIGUSR1
  11 # terminates a "wait" with an error which we need to interpret.
  12 #
  13 # When modifying this code, most of the real logic is in the index_one_file
  14 # function. The rest is cleanup + sempahore plumbing.
  15
  16 # Cleanup temp directory and ensure all child jobs are dead-dead.
  17 function on_exit {
  18   trap "" EXIT USR1  # Avoid reentrancy.
  19
  20   local jobs=$(jobs -p)
  21   if [ -n "$jobs" ]; then
  22     echo -n "Killing outstanding index jobs..."
  23     kill -KILL $(jobs -p)
  24     wait
  25     echo "done"
  26   fi
  27
  28   if [ -f "$DIRECTORY" ]; then
  29     echo -n "Removing temp directory $DIRECTORY..."
  30     rm -rf $DIRECTORY
  31     echo done
  32   fi
  33 }
  34
  35 # Add index to one binary.
  36 function index_one_file {
  37   local file=$1
  38   local basename=$(basename "$file")
  39   local should_index="${SHOULD_INDEX}"
  40
  41   local readelf_out=$(readelf -S "$file")
  42   if [[ $readelf_out =~ "gdb_index" ]]; then
  43     if [ "${REMOVE_INDEX}" = 1 ]; then
  44       objcopy --remove-section .gdb_index "$file"
  45       echo "Removed index from $basename."
  46     else
  47       echo "Skipped $basename -- already contains index."
  48       should_index=0
  49     fi
  50   fi
  51
  52   if [ "${should_index}" = 1 ]; then
  53     local start=$(date +"%s%N")
  54     echo "Adding index to $basename..."
  55
  56     gdb -batch "$file" -ex "save gdb-index $DIRECTORY" -ex "quit"
  57     local index_file="$DIRECTORY/$basename.gdb-index"
  58     if [ -f "$index_file" ]; then
  59       objcopy --add-section .gdb_index="$index_file" \
  60         --set-section-flags .gdb_index=readonly "$file" "$file"
  61       local finish=$(date +"%s%N")
  62       local elappsed=$(((finish - start)/1000000))
  63       echo "   ...$basename indexed. [${elappsed}ms]"
  64     else
  65       echo "   ...$basename unindexable."
  66     fi
  67   fi
  68 }
  69
  70 # Functions that when combined, concurrently index all files in FILES_TO_INDEX
  71 # array. The global FILES_TO_INDEX is declared in the main body of the script.
  72 function async_index {
  73   # Start a background subshell to run the index command.
  74   {
  75     index_one_file $1
  76     kill -SIGUSR1 $$  # $$ resolves to the parent script.
  77     exit 129  # See comment above wait loop at bottom.
  78   } &
  79 }
  80
  81 CUR_FILE_NUM=0
  82 function index_next {
  83   if (( CUR_FILE_NUM >= ${#FILES_TO_INDEX[@]} )); then
  84     return
  85   fi
  86
  87   async_index "${FILES_TO_INDEX[CUR_FILE_NUM]}"
  88   ((CUR_FILE_NUM += 1)) || true
  89 }
  90
  91
  92 ########
  93 ### Main body of the script.
  94
  95 REMOVE_INDEX=0
  96 SHOULD_INDEX=1
  97 while getopts ":f:r" opt; do
  98   case $opt in
  99     f)
 100       REMOVE_INDEX=1
 101       shift
 102       ;;
 103     r)
 104       REMOVE_INDEX=1
 105       SHOULD_INDEX=0
 106       shift
 107       ;;
 108     *)
 109       echo "Invalid option: -$OPTARG" >&2
 110       ;;
 111   esac
 112 done
 113
 114 if [[ ! $# == 1 ]]; then
 115   echo "Usage: $0 [-f] [-r] path-to-binary"
 116   echo "  -f forces replacement of an existing index."
 117   echo "  -r removes the index section."
 118   exit 1
 119 fi
 120
 121 FILENAME="$1"
 122 if [[ ! -f "$FILENAME" ]]; then
 123   echo "Path $FILENAME does not exist."
 124   exit 1
 125 fi
 126
 127 # Ensure we cleanup on on exit.
 128 trap on_exit EXIT
 129
 130 # We're good to go! Create temp directory for index files.
 131 DIRECTORY=$(mktemp -d)
 132 echo "Made temp directory $DIRECTORY."
 133
 134 # Create array with the filename and all shared libraries that
 135 # have the same dirname. The dirname is a signal that these
 136 # shared libraries were part of the same build as the binary.
 137 declare -a FILES_TO_INDEX=($FILENAME
 138  $(ldd "$FILENAME" 2>/dev/null \
 139   | grep $(dirname "$FILENAME") \
 140   | sed "s/.*[ \t]\(.*\) (.*/\1/")
 141 )
 142
 143 # Start concurrent indexing.
 144 trap index_next USR1
 145
 146 # 4 is an arbitrary default. When changing, remember we are likely IO bound
 147 # so basing this off the number of cores is not sensible.
 148 INDEX_TASKS=${INDEX_TASKS:-4}
 149 for ((i=0;i<${INDEX_TASKS};i++)); do
 150   index_next
 151 done
 152
 153 # Do a wait loop. Bash waits that terminate due a trap have an exit
 154 # code > 128. We also ensure that our subshell's "normal" exit occurs with
 155 # an exit code > 128. This allows us to do consider a > 128 exit code as
 156 # an indication that the loop should continue. Unfortunately, it also means
 157 # we cannot use set -e since technically the "wait" is failing.
 158 wait
 159 while (( $? > 128 )); do
 160   wait
 161 done