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 "$file")
  39
  40   local readelf_out=$(readelf -S "$file")
  41   if [[ $readelf_out =~ "gdb_index" ]]; then
  42     echo "Skipped $basename -- already contains index."
  43   else
  44     local start=$(date +"%s%N")
  45     echo "Adding index to $basename..."
  46
  47     gdb -batch "$file" -ex "save gdb-index $DIRECTORY" -ex "quit"
  48     local index_file="$DIRECTORY/$basename.gdb-index"
  49     if [ -f "$index_file" ]; then
  50       objcopy --add-section .gdb_index="$index_file" \
  51         --set-section-flags .gdb_index=readonly "$file" "$file"
  52       local finish=$(date +"%s%N")
  53       local elappsed=$(((finish - start)/1000000))
  54       echo "   ...$basename indexed. [${elappsed}ms]"
  55     else
  56       echo "   ...$basename unindexable."
  57     fi
  58   fi
  59 }
  60
  61 # Functions that when combined, concurrently index all files in FILES_TO_INDEX
  62 # array. The global FILES_TO_INDEX is declared in the main body of the script.
  63 function async_index {
  64   # Start a background subshell to run the index command.
  65   {
  66     index_one_file $1
  67     kill -SIGUSR1 $$  # $$ resolves to the parent script.
  68     exit 129  # See comment above wait loop at bottom.
  69   } &
  70 }
  71
  72 CUR_FILE_NUM=0
  73 function index_next {
  74   if (( CUR_FILE_NUM >= ${#FILES_TO_INDEX[@]} )); then
  75     return
  76   fi
  77
  78   async_index "${FILES_TO_INDEX[CUR_FILE_NUM]}"
  79   ((CUR_FILE_NUM += 1)) || true
  80 }
  81
  82
  83 ########
  84 ### Main body of the script.
  85
  86 if [[ ! $# == 1 ]]; then
  87   echo "Usage: $0 path-to-binary"
  88   exit 1
  89 fi
  90
  91 FILENAME="$1"
  92 if [[ ! -f "$FILENAME" ]]; then
  93   echo "Path $FILENAME does not exist."
  94   exit 1
  95 fi
  96
  97 # Ensure we cleanup on on exit.
  98 trap on_exit EXIT
  99
 100 # We're good to go! Create temp directory for index files.
 101 DIRECTORY=$(mktemp -d)
 102 echo "Made temp directory $DIRECTORY."
 103
 104 # Create array with the filename and all shared libraries that
 105 # have the same dirname. The dirname is a signal that these
 106 # shared libraries were part of the same build as the binary.
 107 declare -a FILES_TO_INDEX=($FILENAME
 108  $(ldd "$FILENAME" 2>/dev/null \
 109   | grep $(dirname "$FILENAME") \
 110   | sed "s/.*[ \t]\(.*\) (.*/\1/")
 111 )
 112
 113 # Start concurrent indexing.
 114 trap index_next USR1
 115
 116 # 4 is an arbitrary default. When changing, remember we are likely IO bound
 117 # so basing this off the number of cores is not sensible.
 118 INDEX_TASKS=${INDEX_TASKS:-4}
 119 for ((i=0;i<${INDEX_TASKS};i++)); do
 120   index_next
 121 done
 122
 123 # Do a wait loop. Bash waits that terminate due a trap have an exit
 124 # code > 128. We also ensure that our subshell's "normal" exit occurs with
 125 # an exit code > 128. This allows us to do consider a > 128 exit code as
 126 # an indication that the loop should continue. Unfortunately, it also means
 127 # we cannot use set -e since technically the "wait" is failing.
 128 wait
 129 while (( $? > 128 )); do
 130   wait
 131 done