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#!/bin/sh
# SPDX-License-Identifier: 0BSD
###############################################################################
#
# Check liblzma_*.map for certain types of errors.
#
# liblzma_generic.map is for FreeBSD and Solaris and possibly others
# except GNU/Linux.
#
# liblzma_linux.map is for GNU/Linux only. This and the matching extra code
# in the .c files make liblzma >= 5.2.7 compatible with binaries that were
# linked against ill-patched liblzma in RHEL/CentOS 7. By providing the
# compatibility in official XZ Utils release will hopefully prevent people
# from further copying the broken patch to other places when they want
# compatibility with binaries linked on RHEL/CentOS 7. The long version
# of the story:
#
# RHEL/CentOS 7 shipped with 5.1.2alpha, including the threaded
# encoder that is behind #ifdef LZMA_UNSTABLE in the API headers.
# In 5.1.2alpha these symbols are under XZ_5.1.2alpha in liblzma.map.
# API/ABI compatibility tracking isn't done between development
# releases so newer releases didn't have XZ_5.1.2alpha anymore.
#
# Later RHEL/CentOS 7 updated xz to 5.2.2 but they wanted to keep
# the exported symbols compatible with 5.1.2alpha. After checking
# the ABI changes it turned out that >= 5.2.0 ABI is backward
# compatible with the threaded encoder functions from 5.1.2alpha
# (but not vice versa as fixes and extensions to these functions
# were made between 5.1.2alpha and 5.2.0).
#
# In RHEL/CentOS 7, XZ Utils 5.2.2 was patched with
# xz-5.2.2-compat-libs.patch to modify liblzma.map:
#
# - XZ_5.1.2alpha was added with lzma_stream_encoder_mt and
# lzma_stream_encoder_mt_memusage. This matched XZ Utils 5.1.2alpha.
#
# - XZ_5.2 was replaced with XZ_5.2.2. It is clear that this was
# an error; the intention was to keep using XZ_5.2 (XZ_5.2.2
# has never been used in XZ Utils). So XZ_5.2.2 lists all
# symbols that were listed under XZ_5.2 before the patch.
# lzma_stream_encoder_mt and _mt_memusage are included too so
# they are listed both here and under XZ_5.1.2alpha.
#
# The patch didn't add any __asm__(".symver ...") lines to the .c
# files. Thus the resulting liblzma.so exports the threaded encoder
# functions under XZ_5.1.2alpha only. Listing the two functions
# also under XZ_5.2.2 in liblzma.map has no effect without
# matching .symver lines.
#
# The lack of XZ_5.2 in RHEL/CentOS 7 means that binaries linked
# against unpatched XZ Utils 5.2.x won't run on RHEL/CentOS 7.
# This is unfortunate but this alone isn't too bad as the problem
# is contained within RHEL/CentOS 7 and doesn't affect users
# of other distributions. It could also be fixed internally in
# RHEL/CentOS 7.
#
# The second problem is more serious: In XZ Utils 5.2.2 the API
# headers don't have #ifdef LZMA_UNSTABLE for obvious reasons.
# This is true in RHEL/CentOS 7 version too. Thus now programs
# using new APIs can be compiled without an extra #define. However,
# the programs end up depending on symbol version XZ_5.1.2alpha
# (and possibly also XZ_5.2.2) instead of XZ_5.2 as they would
# with an unpatched XZ Utils 5.2.2. This means that such binaries
# won't run on other distributions shipping XZ Utils >= 5.2.0 as
# they don't provide XZ_5.1.2alpha or XZ_5.2.2; they only provide
# XZ_5.2 (and XZ_5.0). (This includes RHEL/CentOS 8 as the patch
# luckily isn't included there anymore with XZ Utils 5.2.4.)
#
# Binaries built by RHEL/CentOS 7 users get distributed and then
# people wonder why they don't run on some other distribution.
# Seems that people have found out about the patch and been copying
# it to some build scripts, seemingly curing the symptoms but
# actually spreading the illness further and outside RHEL/CentOS 7.
# Adding compatibility in an official XZ Utils release should work
# as a vaccine against this ill patch and stop it from spreading.
# The vaccine is kept GNU/Linux-only as other OSes should be immune
# (hopefully it hasn't spread via some build script to other OSes).
#
# Author: Lasse Collin
#
###############################################################################
LC_ALL=C
export LC_ALL
STATUS=0
cd "$(dirname "$0")"
# Get the list of symbols that aren't defined in liblzma_generic.map.
SYMS=$(sed -n 's/^extern LZMA_API([^)]*) \([a-z0-9_]*\)(.*$/\1;/p' \
api/lzma/*.h \
| sort \
| grep -Fve "$(sed '/[{}:*]/d;/^$/d;s/^ //' liblzma_generic.map)")
# Check that there are no old alpha or beta versions listed.
VER=$(cd ../.. && sh build-aux/version.sh)
NAMES=
case $VER in
*alpha | *beta)
NAMES=$(sed -n 's/^.*XZ_\([^ ]*\)\(alpha\|beta\) .*$/\1\2/p' \
liblzma_generic.map | grep -Fv "$VER")
;;
esac
# Check for duplicate lines. It can catch missing dependencies.
DUPS=$(sort liblzma_generic.map | sed '/^$/d;/^global:$/d' | uniq -d)
# Check that liblzma_linux.map is in sync with liblzma_generic.map.
# The RHEL/CentOS 7 compatibility symbols are in a fixed location
# so it makes it easy to remove them for comparison with liblzma_generic.map.
#
# NOTE: Putting XZ_5.2 before the compatibility symbols XZ_5.1.2alpha
# and XZ_5.2.2 in liblzma_linux.map is important: If liblzma_linux.map is
# incorrectly used without #define HAVE_SYMBOL_VERSIONS_LINUX, only the first
# occurrence of each function name will be used from liblzma_linux.map;
# the rest are ignored by the linker. Thus having XZ_5.2 before the
# compatibility symbols means that @@XZ_5.2 will be used for the symbols
# listed under XZ_5.2 {...} and the same function names later in
# the file under XZ_5.1.2alpha {...} and XZ_5.2.2 {...} will be
# ignored (@XZ_5.1.2alpha or @XZ_5.2.2 won't be added at all when
# the #define HAVE_SYMBOL_VERSIONS_LINUX isn't used).
IN_SYNC=
if ! sed '111,125d' liblzma_linux.map \
| cmp -s - liblzma_generic.map; then
IN_SYNC=no
fi
# Print error messages if needed.
if test -n "$SYMS$NAMES$DUPS$IN_SYNC"; then
echo
echo 'validate_map.sh found problems from liblzma_*.map:'
echo
if test -n "$SYMS"; then
echo 'liblzma_generic.map lacks the following symbols:'
echo "$SYMS"
echo
fi
if test -n "$NAMES"; then
echo 'Obsolete alpha or beta version names:'
echo "$NAMES"
echo
fi
if test -n "$DUPS"; then
echo 'Duplicate lines:'
echo "$DUPS"
echo
fi
if test -n "$IN_SYNC"; then
echo "liblzma_generic.map and liblzma_linux.map aren't in sync"
echo
fi
STATUS=1
fi
# Exit status is 1 if problems were found, 0 otherwise.
exit "$STATUS"
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