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openbsd-src/lib/check_sym

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#!/bin/ksh
# $OpenBSD: check_sym,v 1.13 2024/09/03 08:49:16 tb Exp $
#
# Copyright (c) 2016,2019,2022 Philip Guenther <guenther@openbsd.org>
#
# Permission to use, copy, modify, and distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
#
#
# check_sym -- compare the symbols and external function references in two
# versions of a library
#
# SYNOPSIS
# check_sym [-chkSv] [old [new]]
#
# DESCRIPTION
# Library developers need to be aware when they have changed the
# ABI of a library. To assist them, check_sym examines two versions
# of a shared library and reports changes to the following:
# * the set of exported symbols and their strengths
# * the set of undefined symbols referenced
# * the set of lazily-resolved functions (PLT)
#
# In each case, additions and removals are reported; for exported
# symbols it also reports when a symbol is weakened or strengthened.
#
# With the -S option, a similar analysis is done but for the static lib.
#
# The shared libraries to compare can be specified on the
# command-line. Otherwise, check_sym expects to be run from the
# source directory of a library with a shlib_version file specifying
# the version being built and the new library in the obj subdirectory.
# If the old library to compare against wasn't specified either then
# check_sym will take the highest version of that library in the
# *current* directory, or the highest version of that library in
# /usr/lib if it wasn't present in the current directory.
#
# By default, check_sym places all its intermediate files in a
# temporary directory and removed it on exit. They contain useful
# details for understanding what changed, so if the -k option is used
# they will instead be placed in /tmp/ and left behind. If any of
# them cannot be created by the user, the command will fail. The
# files left behind by the -k option can be cleaned up by invoking
# check_syms with the -c option.
#
# The -v option enables verbose output, showing relocation counts.
#
# The *basic* rules of thumb for library versions are: if you
# * stop exporting a symbol, or
# * change the size of a data symbol
# * start exporting a symbol that an inter-dependent library needs
# then you need to bump the MAJOR version of the library.
#
# Otherwise, if you:
# * start exporting a symbol
# then you need to bump the MINOR version of the library.
#
# SEE ALSO
# readelf(1), elf(5)
#
# AUTHORS
# Philip Guenther <guenther@openbsd.org>
#
# CAVEATS
# The elf format is infinitely extendable, but check_sym only
# handles a few weirdnesses. Running it on or against new archs
# may result in meaningless results.
#
# BUGS
# While the author stills find the intermediate files useful,
# most people won't. By default they should be placed in a
# temp directory and removed.
#
get_lib_name()
{
sed -n '/^[ ]*LIB[ ]*=/{ s/^[^=]*=[ ]*\([^ ]*\).*/\1/p; q;}' "$@"
}
pick_highest()
{
old=
omaj=-1
omin=0
for i
do
[[ -f $i ]] || continue
maj=${i%.*}; maj=${maj##*.}
min=${i##*.}
if [[ $maj -gt $omaj || ( $maj -eq $omaj && $min -gt $omin ) ]]
then
old=$i
omaj=$maj
omin=$min
fi
done
[[ $old != "" ]]
}
fail() { echo "$*" >&2; exit 1; }
usage()
{
usage="usage: check_sym [-chkSv] [old [new]]"
[[ $# -eq 0 ]] || fail "check_sym: $*
$usage"
echo "$usage"
exit 0
}
#
# Output helpers
#
data_sym_changes()
{
join "$@" | awk '$2 != $3 { print $1 " " $2 " --> " $3 }'
}
output_if_not_empty()
{
leader=$1
shift
if "$@" | grep -q .
then
echo "$leader"
"$@" | sed 's:^: :'
echo
fi
}
#
# Dynamic library routines
#
dynamic_collect()
{
readelf -sW $old | filt_symtab > $odir/Ds1
readelf -sW $new | filt_symtab > $odir/Ds2
readelf -rW $old > $odir/r1
readelf -rW $new > $odir/r2
case $(readelf -h $new | grep '^ *Machine:') in
*MIPS*) cpu=mips64
gotsym1=$(readelf -d $old | awk '$2 ~ /MIPS_GOTSYM/{print $3}')
gotsym2=$(readelf -d $new | awk '$2 ~ /MIPS_GOTSYM/{print $3}')
;;
*HPPA*) cpu=hppa;;
*) cpu=dontcare;;
esac
}
jump_slots()
{
case $cpu in
hppa) awk '/IPLT/ && $5 != ""{print $5}' r$1
;;
mips64) # the $((gotsym$1)) converts hex to decimal
awk -v g=$((gotsym$1)) \
'/^Symbol table ..symtab/{exit}
$6 == "PROTECTED" { next }
$1+0 >= g && $4 == "FUNC" {print $8}' Ds$1
;;
*) awk '/JU*MP_SL/ && $5 != ""{print $5}' r$1
;;
esac | sort -o j$1
}
dynamic_sym()
{
awk -v s=$1 '/^Symbol table ..symtab/{exit}
! /^ *[1-9]/ {next}
$5 == "LOCAL" {next}
$7 == "UND" {print $8 | ("sort -o DU" s); next }
$5 == "GLOBAL" {print $8 | ("sort -o DS" s) }
$5 == "WEAK" {print $8 | ("sort -o DW" s) }
$4 == "OBJECT" {print $8, $3 | ("sort -o DO" s) }
{print $8 | ("sort -o D" s)
print $4, $5, $6, $8}' Ds$1 | sort -o d$1
}
static_sym()
{
awk '/^Symbol table ..symtab/{s=1}
/LOCAL/{next}
s&&/^ *[1-9]/{print $4, $5, $6, $8}' Ds$1 | sort -o s$1
}
dynamic_analysis()
{
jump_slots $1
dynamic_sym $1
#static_sym $1
comm -23 j$1 DU$1 >J$1
return 0
}
dynamic_output()
{
if cmp -s d[12] && cmp -s DO[12]
then
printf "No dynamic export changes\n"
else
printf "Dynamic export changes:\n"
output_if_not_empty "added:" comm -13 D[12]
output_if_not_empty "removed:" comm -23 D[12]
output_if_not_empty "weakened:" comm -12 DS1 DW2
output_if_not_empty "strengthened:" comm -12 DW1 DS2
output_if_not_empty "data object sizes changes:" \
data_sym_changes DO[12]
fi
if ! cmp -s DU[12]
then
printf "External reference changes:\n"
output_if_not_empty "added:" comm -13 DU[12]
output_if_not_empty "removed:" comm -23 DU[12]
fi
if $verbose; then
printf "\nReloc counts:\nbefore:\n"
grep ^R r1
printf "\nafter:\n"
grep ^R r2
fi
output_if_not_empty "PLT added:" comm -13 J[12]
output_if_not_empty "PLT removed:" comm -23 J[12]
}
#
# Static library routines
#
static_collect()
{
readelf -sW $old | filt_ret | filt_symtab > $odir/Ss1
readelf -sW $new | filt_ret | filt_symtab > $odir/Ss2
}
static_analysis()
{
awk -v s=$1 '!/^ *[1-9]/{next}
$5 == "LOCAL" {next}
$7 == "UND" {print $8 | ("sort -uo SU" s); next }
$6 == "HIDDEN" {print $8 | ("sort -uo SH" s) }
$5 == "GLOBAL" {print $8 | ("sort -o SS" s) }
$5 == "WEAK" {print $8 | ("sort -o SW" s) }
$4 == "OBJECT" {print $8, $3 | ("sort -o SO" s) }
{print $8 | ("sort -o S" s)
print $4, $5, $6, $8}' Ss$1 | sort -o s$1
grep -v '^_' SH$1 >Sh$1 || :
}
static_output()
{
output_if_not_empty "hidden but not reserved:" comm -13 Sh[12]
if cmp -s s[12] && cmp -s SO[12]
then
printf "No static export changes\n"
else
printf "Static export changes:\n"
output_if_not_empty "added:" comm -13 S[12]
output_if_not_empty "removed:" comm -23 S[12]
output_if_not_empty "weakened:" comm -12 SS1 SW2
output_if_not_empty "strengthened:" comm -12 SW1 SS2
output_if_not_empty "data object sizes changes:" \
data_sym_changes SO[12]
fi
if ! cmp -s SU[12]
then
printf "External reference changes:\n"
output_if_not_empty "added:" comm -13 SU[12]
output_if_not_empty "removed:" comm -23 SU[12]
fi
}
unset odir
file_list={D{,O,S,s,W,U},J,d,j,r}{1,2}
static_file_list={S{,H,h,O,S,U,W},U,s}{1,2}
keep_temp=false
dynamic=true
static=false
verbose=false
do_static() { static=true dynamic=false file_list=$static_file_list; }
while getopts :chkSv opt "$@"
do
case $opt in
c) rm -f /tmp/$file_list
exit 0;;
h) usage;;
k) keep_temp=true;;
S) do_static;;
v) verbose=true;;
\?) usage "unknown option -- $OPTARG";;
esac
done
shift $((OPTIND - 1))
[[ $# -gt 2 ]] && usage "too many arguments"
# Old library?
if ! $static && [[ $1 = ?(*/)lib*.so* ]]
then
[[ -f $1 ]] || fail "$1 doesn't exist"
old=$1
lib=${old##*/}
lib=${lib%%.so.*}
shift
elif [[ $1 = ?(*/)lib*.a ]]
then
# woo hoo, static library mode
do_static
if [[ -f $1 ]]
then
old=$1
lib=${old##*/}
elif [[ $1 = lib*.a && -f /usr/lib/$1 ]]
then
old=/usr/lib/$1
lib=$1
else
fail "$1 doesn't exist"
fi
lib=${lib%%.a}
shift
else
# try determining it from the current directory
if [[ -f Makefile ]] && lib=$(get_lib_name Makefile) &&
[[ $lib != "" ]]
then
lib=lib$lib
else
lib=libc
fi
# Is there a copy of that lib in the current directory?
# If so, use the highest numbered one
if ! $static &&
! pick_highest $lib.so.* &&
! pick_highest /usr/lib/$lib.so.*
then
fail "unable to find $lib.so.*"
elif $static
then
old=/usr/lib/${lib}.a
[[ -f $old ]] || fail "$old doesn't exist"
fi
fi
# New library?
if [[ $1 = ?(*/)lib*.so* ]] ||
{ $static && [[ $1 = ?(*/)lib*.a ]]; }
then
new=$1
shift
elif $static
then
new=obj/${lib}.a
else
# Dig info out of the just built library
. ./shlib_version
new=obj/${lib}.so.${major}.${minor}
fi
[[ -f $new ]] || fail "$new doesn't exist"
# Filter the output of readelf -s to be easier to parse by removing a
# field that only appears on some symbols: [<other>: 88]
# Not really arch-specific, but I've only seen it on alpha
filt_symtab() { sed 's/\[<other>: [0-9a-f]*\]//'; }
filt_ret() { egrep -v ' (__retguard_[0-9]+|__llvm_retpoline_[a-z]+[0-9]*)$'; }
if $keep_temp
then
# precreate all the files we'll use, but with noclobber set to avoid
# symlink attacks
odir=/tmp
files=
trap 'ret=$?; rm -f $files; exit $ret' 1 2 15 ERR
else
trap 'ret=$?; rm -rf "$odir"; exit $ret' 0 1 2 15 ERR
odir=$(mktemp -dt check_sym.XXXXXXXXXX)
fi
set -C
for i in $odir/$file_list
do
rm -f $i
3>$i
files="$files $i"
done
set +C
#
# Collect data
#
$dynamic && dynamic_collect
$static && static_collect
# Now that we're done accessing $old and $new (which could be
# relative paths), chdir into our work directory, whatever it is
cd $odir
#
# Do The Job
#
for i in 1 2
do
$dynamic && dynamic_analysis $i
$static && static_analysis $i
done
{
echo "$old --> $new"
! $dynamic || dynamic_output
! $static || static_output
}