src/liblzma/validate_map.sh

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