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      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
    132