path: root/lib/check_sym

#!/bin/ksh
#  $OpenBSD: check_sym,v 1.12 2024/08/15 01:25:13 guenther 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
}