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-rw-r--r--src/liblzma/validate_map.sh113
1 files changed, 105 insertions, 8 deletions
diff --git a/src/liblzma/validate_map.sh b/src/liblzma/validate_map.sh
index 3aee4668..2bf6f8b9 100644
--- a/src/liblzma/validate_map.sh
+++ b/src/liblzma/validate_map.sh
@@ -2,7 +2,79 @@
###############################################################################
#
-# Check liblzma.map for certain types of errors
+# 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
#
@@ -18,11 +90,11 @@ STATUS=0
cd "$(dirname "$0")"
-# Get the list of symbols that aren't defined in liblzma.map.
+# Get the list of symbols that aren't defined in liblzma_generic.map.
SYMS=$(sed -n 's/^extern LZMA_API([^)]*) \([a-z0-9_]*\)(.*$/\1;/p' \
api/lzma/*.h \
| sort \
- | grep -Fve "$(sed '/[{}:*]/d;/^$/d;s/^ //' liblzma.map)")
+ | grep -Fve "$(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)
@@ -30,21 +102,41 @@ NAMES=
case $VER in
*alpha | *beta)
NAMES=$(sed -n 's/^.*XZ_\([^ ]*\)\(alpha\|beta\) .*$/\1\2/p' \
- liblzma.map | grep -Fv "$VER")
+ liblzma_generic.map | grep -Fv "$VER")
;;
esac
# Check for duplicate lines. It can catch missing dependencies.
-DUPS=$(sort liblzma.map | sed '/^$/d;/^global:$/d' | uniq -d)
+DUPS=$(sort liblzma_generic.map | sed '/^$/d;/^global:$/d' | uniq -d)
+
+# Check that liblzma_linux.map is in sync with liblzma_generic.map.
+# The RHEL/CentOS 7 compatibility symbols are in a fixed location
+# so it makes it easy to remove them for comparison with liblzma_generic.map.
+#
+# NOTE: Putting XZ_5.2 before the compatibility symbols XZ_5.1.2alpha
+# and XZ_5.2.2 in liblzma_linux.map is important: If liblzma_linux.map is
+# incorrectly used without #define HAVE_SYMBOL_VERSIONS_LINUX, only the first
+# occurrence of each function name will be used from liblzma_linux.map;
+# the rest are ignored by the linker. Thus having XZ_5.2 before the
+# compatibility symbols means that @@XZ_5.2 will be used for the symbols
+# listed under XZ_5.2 {...} and the same function names later in
+# the file under XZ_5.1.2alpha {...} and XZ_5.2.2 {...} will be
+# ignored (@XZ_5.1.2alpha or @XZ_5.2.2 won't be added at all when
+# the #define HAVE_SYMBOL_VERSIONS_LINUX isn't used).
+IN_SYNC=
+if ! sed '109,123d' liblzma_linux.map \
+ | cmp -s - liblzma_generic.map; then
+ IN_SYNC=no
+fi
# Print error messages if needed.
-if test -n "$SYMS$NAMES$DUPS"; then
+if test -n "$SYMS$NAMES$DUPS$IN_SYNC"; then
echo
- echo 'validate_map.sh found problems from liblzma.map:'
+ echo 'validate_map.sh found problems from liblzma_*.map:'
echo
if test -n "$SYMS"; then
- echo 'liblzma.map lacks the following symbols:'
+ echo 'liblzma_generic.map lacks the following symbols:'
echo "$SYMS"
echo
fi
@@ -61,6 +153,11 @@ if test -n "$SYMS$NAMES$DUPS"; then
echo
fi
+ if test -n "$IN_SYNC"; then
+ echo "liblzma_generic.map and liblzma_linux.map aren't in sync"
+ echo
+ fi
+
STATUS=1
fi