src/liblzma/validate_map.sh

   1 #!/bin/sh
   2 # SPDX-License-Identifier: 0BSD
   3
   4 ###############################################################################
   5 #
   6 # Check liblzma_*.map for certain types of errors.
   7 #
   8 # liblzma_generic.map is for FreeBSD and Solaris and possibly others
   9 # except GNU/Linux.
  10 #
  11 # liblzma_linux.map is for GNU/Linux only. This and the matching extra code
  12 # in the .c files make liblzma >= 5.2.7 compatible with binaries that were
  13 # linked against ill-patched liblzma in RHEL/CentOS 7. By providing the
  14 # compatibility in official XZ Utils release will hopefully prevent people
  15 # from further copying the broken patch to other places when they want
  16 # compatibility with binaries linked on RHEL/CentOS 7. The long version
  17 # of the story:
  18 #
  19 #     RHEL/CentOS 7 shipped with 5.1.2alpha, including the threaded
  20 #     encoder that is behind #ifdef LZMA_UNSTABLE in the API headers.
  21 #     In 5.1.2alpha these symbols are under XZ_5.1.2alpha in liblzma.map.
  22 #     API/ABI compatibility tracking isn't done between development
  23 #     releases so newer releases didn't have XZ_5.1.2alpha anymore.
  24 #
  25 #     Later RHEL/CentOS 7 updated xz to 5.2.2 but they wanted to keep
  26 #     the exported symbols compatible with 5.1.2alpha. After checking
  27 #     the ABI changes it turned out that >= 5.2.0 ABI is backward
  28 #     compatible with the threaded encoder functions from 5.1.2alpha
  29 #     (but not vice versa as fixes and extensions to these functions
  30 #     were made between 5.1.2alpha and 5.2.0).
  31 #
  32 #     In RHEL/CentOS 7, XZ Utils 5.2.2 was patched with
  33 #     xz-5.2.2-compat-libs.patch to modify liblzma.map:
  34 #
  35 #       - XZ_5.1.2alpha was added with lzma_stream_encoder_mt and
  36 #         lzma_stream_encoder_mt_memusage. This matched XZ Utils 5.1.2alpha.
  37 #
  38 #       - XZ_5.2 was replaced with XZ_5.2.2. It is clear that this was
  39 #         an error; the intention was to keep using XZ_5.2 (XZ_5.2.2
  40 #         has never been used in XZ Utils). So XZ_5.2.2 lists all
  41 #         symbols that were listed under XZ_5.2 before the patch.
  42 #         lzma_stream_encoder_mt and _mt_memusage are included too so
  43 #         they are listed both here and under XZ_5.1.2alpha.
  44 #
  45 #     The patch didn't add any __asm__(".symver ...") lines to the .c
  46 #     files. Thus the resulting liblzma.so exports the threaded encoder
  47 #     functions under XZ_5.1.2alpha only. Listing the two functions
  48 #     also under XZ_5.2.2 in liblzma.map has no effect without
  49 #     matching .symver lines.
  50 #
  51 #     The lack of XZ_5.2 in RHEL/CentOS 7 means that binaries linked
  52 #     against unpatched XZ Utils 5.2.x won't run on RHEL/CentOS 7.
  53 #     This is unfortunate but this alone isn't too bad as the problem
  54 #     is contained within RHEL/CentOS 7 and doesn't affect users
  55 #     of other distributions. It could also be fixed internally in
  56 #     RHEL/CentOS 7.
  57 #
  58 #     The second problem is more serious: In XZ Utils 5.2.2 the API
  59 #     headers don't have #ifdef LZMA_UNSTABLE for obvious reasons.
  60 #     This is true in RHEL/CentOS 7 version too. Thus now programs
  61 #     using new APIs can be compiled without an extra #define. However,
  62 #     the programs end up depending on symbol version XZ_5.1.2alpha
  63 #     (and possibly also XZ_5.2.2) instead of XZ_5.2 as they would
  64 #     with an unpatched XZ Utils 5.2.2. This means that such binaries
  65 #     won't run on other distributions shipping XZ Utils >= 5.2.0 as
  66 #     they don't provide XZ_5.1.2alpha or XZ_5.2.2; they only provide
  67 #     XZ_5.2 (and XZ_5.0). (This includes RHEL/CentOS 8 as the patch
  68 #     luckily isn't included there anymore with XZ Utils 5.2.4.)
  69 #
  70 #     Binaries built by RHEL/CentOS 7 users get distributed and then
  71 #     people wonder why they don't run on some other distribution.
  72 #     Seems that people have found out about the patch and been copying
  73 #     it to some build scripts, seemingly curing the symptoms but
  74 #     actually spreading the illness further and outside RHEL/CentOS 7.
  75 #     Adding compatibility in an official XZ Utils release should work
  76 #     as a vaccine against this ill patch and stop it from spreading.
  77 #     The vaccine is kept GNU/Linux-only as other OSes should be immune
  78 #     (hopefully it hasn't spread via some build script to other OSes).
  79 #
  80 # Author: Lasse Collin
  81 #
  82 ###############################################################################
  83
  84 LC_ALL=C
  85 export LC_ALL
  86
  87 STATUS=0
  88
  89 cd "$(dirname "$0")"
  90
  91 # Get the list of symbols that aren't defined in liblzma_generic.map.
  92 SYMS=$(sed -n 's/^extern LZMA_API([^)]*) \([a-z0-9_]*\)(.*$/\1;/p' \
  93                 api/lzma/*.h \
  94         | sort \
  95         | grep -Fve "$(sed '/[{}:*]/d;/^$/d;s/^ //' liblzma_generic.map)")
  96
  97 # Check that there are no old alpha or beta versions listed.
  98 VER=$(cd ../.. && sh build-aux/version.sh)
  99 NAMES=
 100 case $VER in
 101         *alpha | *beta)
 102                 NAMES=$(sed -n 's/^.*XZ_\([^ ]*\)\(alpha\|beta\) .*$/\1\2/p' \
 103                         liblzma_generic.map | grep -Fv "$VER")
 104                 ;;
 105 esac
 106
 107 # Check for duplicate lines. It can catch missing dependencies.
 108 DUPS=$(sort liblzma_generic.map | sed '/^$/d;/^global:$/d' | uniq -d)
 109
 110 # Check that liblzma_linux.map is in sync with liblzma_generic.map.
 111 # The RHEL/CentOS 7 compatibility symbols are in a fixed location
 112 # so it makes it easy to remove them for comparison with liblzma_generic.map.
 113 #
 114 # NOTE: Putting XZ_5.2 before the compatibility symbols XZ_5.1.2alpha
 115 # and XZ_5.2.2 in liblzma_linux.map is important: If liblzma_linux.map is
 116 # incorrectly used without #define HAVE_SYMBOL_VERSIONS_LINUX, only the first
 117 # occurrence of each function name will be used from liblzma_linux.map;
 118 # the rest are ignored by the linker. Thus having XZ_5.2 before the
 119 # compatibility symbols means that @@XZ_5.2 will be used for the symbols
 120 # listed under XZ_5.2 {...} and the same function names later in
 121 # the file under XZ_5.1.2alpha {...} and XZ_5.2.2 {...} will be
 122 # ignored (@XZ_5.1.2alpha or @XZ_5.2.2 won't be added at all when
 123 # the #define HAVE_SYMBOL_VERSIONS_LINUX isn't used).
 124 IN_SYNC=
 125 if ! sed '111,125d' liblzma_linux.map \
 126                 | cmp -s - liblzma_generic.map; then
 127         IN_SYNC=no
 128 fi
 129
 130 # Print error messages if needed.
 131 if test -n "$SYMS$NAMES$DUPS$IN_SYNC"; then
 132         echo
 133         echo 'validate_map.sh found problems from liblzma_*.map:'
 134         echo
 135
 136         if test -n "$SYMS"; then
 137                 echo 'liblzma_generic.map lacks the following symbols:'
 138                 echo "$SYMS"
 139                 echo
 140         fi
 141
 142         if test -n "$NAMES"; then
 143                 echo 'Obsolete alpha or beta version names:'
 144                 echo "$NAMES"
 145                 echo
 146         fi
 147
 148         if test -n "$DUPS"; then
 149                 echo 'Duplicate lines:'
 150                 echo "$DUPS"
 151                 echo
 152         fi
 153
 154         if test -n "$IN_SYNC"; then
 155                 echo "liblzma_generic.map and liblzma_linux.map aren't in sync"
 156                 echo
 157         fi
 158
 159         STATUS=1
 160 fi
 161
 162 # Exit status is 1 if problems were found, 0 otherwise.
 163 exit "$STATUS"