Annotation of src/lib/check_sym, Revision 1.6
1.1 guenther 1: #!/bin/ksh
1.6 ! guenther 2: # $OpenBSD: check_sym,v 1.5 2017/08/11 17:58:21 guenther Exp $
1.3 guenther 3: #
4: # Copyright (c) 2016 Philip Guenther <guenther@openbsd.org>
5: #
6: # Permission to use, copy, modify, and distribute this software for any
7: # purpose with or without fee is hereby granted, provided that the above
8: # copyright notice and this permission notice appear in all copies.
9: #
10: # THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
11: # WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12: # MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
13: # ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14: # WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15: # ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16: # OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17: #
1.1 guenther 18: #
19: # check_sym -- compare the symbols and external function references in two
20: # versions of a shared library
21: #
22: # SYNOPSIS
23: # check_sym [-ch] [old [new]]
24: #
25: # DESCRIPTION
26: # Library developers need to be aware when they have changed the
27: # ABI of a library. To assist them, check_sym examines two versions
28: # of a shared library and reports changes to the following:
29: # * the set of exported symbols and their strengths
30: # * the set of undefined symbols referenced
31: # * the set of lazily-resolved functions (PLT)
32: #
33: # In each case, additions and removals are reported; for exported
34: # symbols it also reports when a symbol is weakened or strengthened.
35: #
36: # The shared libraries to compare can be specified on the
37: # command-line. Otherwise, check_sym expects to be run from the
1.6 ! guenther 38: # source directory of a library with a shlib_version file specifying
1.1 guenther 39: # the version being built and the new library in the obj subdirectory.
1.6 ! guenther 40: # If the old library to compare against wasn't specified either then
1.1 guenther 41: # check_sym will take the highest version of that library in the
42: # *current* directory, or the highest version of that library in
43: # /usr/lib if it wasn't present in the current directory.
44: #
45: # check_sym uses fixed names in /tmp for its intermediate files,
46: # as they contain useful details for those trying to understand
47: # what changed. If any of them cannot be created by the user,
48: # the command will fail. The files can be cleaned up using
49: # the -c option.
50: #
51: #
52: # The *basic* rules of thumb for library versions are: if you
53: # * stop exporting a symbol, or
54: # * change the size of a data symbol (not reported by check_sym)
55: # * start exporting a symbol that an inter-dependent library needs
56: # then you need to bump the MAJOR version of the library.
57: #
58: # Otherwise, if you:
59: # * start exporting a symbol
60: # then you need to bump the MINOR version of the library.
61: #
62: # SEE ALSO
63: # readelf(1), elf(5)
64: #
65: # AUTHORS
66: # Philip Guenther <guenther@openbsd.org>
67: #
68: # CAVEATS
69: # The elf format is infinitely extendable, but check_sym only
70: # handles a few weirdnesses. Running it on or against new archs
71: # may result in meaningless results.
72: #
73: # BUGS
74: # Should report changes in the size of exported data objects.
75: #
1.5 guenther 76: # While the author stills find the intermediate files useful,
77: # most people won't. By default they should be placed in a
78: # temp directory and removed.
79: #
1.1 guenther 80:
81: get_lib_name()
82: {
83: sed -n 's/^[ ]*LIB[ ]*=[ ]*\([^ ]*\).*/\1/p' "$@"
84: }
85:
86: pick_highest()
87: {
88: old=
89: omaj=-1
90: omin=0
91: for i
92: do
93: [[ -f $i ]] || continue
94: maj=${i%.*}; maj=${maj##*.}
95: min=${i##*.}
96: if [[ $maj -gt $omaj || ( $maj -eq $omaj && $min -gt $omin ) ]]
97: then
98: old=$i
99: omaj=$maj
100: omin=$min
101: fi
102: done
103: [[ $old != "" ]]
104: }
105:
1.5 guenther 106: usage()
107: {
108: usage="usage: check_sym [-chv] [old [new]]"
109: if [[ $# -gt 0 ]]
110: then
111: echo "check_sym: $@
112: $usage" >&2
113: exit 1
114: fi
115: echo "$usage"
116: exit 0
117: }
118:
1.4 guenther 119: file_list=/tmp/{D{,S,W},J,S,U,d,j,r,s}{1,2}
1.1 guenther 120:
1.5 guenther 121: verbose=false
122: while getopts :chv opt "$@"
123: do
124: case $opt in
125: h) usage;;
126: c) rm -f $file_list
127: exit 0;;
128: v) verbose=true;;
129: \?) usage "unknown option -- $OPTARG";;
130: esac
131: done
132: shift $((OPTIND - 1))
133: [[ $# -gt 2 ]] && usage "too many arguments"
1.1 guenther 134:
135: # Old library?
136: if [[ $1 = ?(*/)lib*.so* ]]
137: then
138: if [[ ! -f $1 ]]
139: then
140: echo "$1 doesn't exist" >&2
141: exit 1
142: fi
143: old=$1
144: lib=${old##*/}
145: lib=${lib%%.so.*}
146: shift
147: else
148: # try determining it from the current directory
149: if [[ -f Makefile ]] && lib=$(get_lib_name Makefile) &&
150: [[ $lib != "" ]]
151: then
152: lib=lib$lib
153: else
154: lib=libc
155: fi
156:
157: # Is there a copy of that lib in the current directory?
158: # If so, use the highest numbered one
159: if ! pick_highest $lib.so.* && ! pick_highest /usr/lib/$lib.so.*
160: then
161: echo "unable to find $lib.so.*" >&2
162: exit 1
163: fi
164: fi
165:
166: # New library?
167: if [[ $1 = ?(*/)lib*.so* ]]
168: then
169: new=$1
170: shift
171: else
172: # Dig info out of the just built library
173: . ./shlib_version
174: new=obj/${lib}.so.${major}.${minor}
175: fi
1.5 guenther 176: if [[ ! -f $new ]]
177: then
178: echo "$new doesn't exist" >&2
179: exit 1
180: fi
1.1 guenther 181:
182: # Filter the output of readelf -s to be easier to parse by removing a
183: # field that only appears on some symbols: [<other>: 88]
184: # Not really arch-specific, but I've only seen it on alpha
185: filt_symtab() {
186: sed 's/\[<other>: [0-9a-f]*\]//'
187: }
188:
189: # precreate all the files we'll use, but with noclobber set to avoid
190: # symlink attacks
191: set -C
192: files=
193: trap 'rm -f $files' 1 2 15 ERR
194: for i in $file_list
195: do
196: rm -f $i
197: 3>$i
198: files="$files $i"
199: done
200: set +C
201:
202: readelf -rW $old > /tmp/r1
203: readelf -rW $new > /tmp/r2
204:
205: readelf -sW $old | filt_symtab > /tmp/s1
206: readelf -sW $new | filt_symtab > /tmp/s2
207:
208:
1.4 guenther 209: cpu=$(uname -p)
1.1 guenther 210: if [[ $cpu = mips64* ]]
211: then
1.4 guenther 212: gotsym1=$(readelf -d $old | awk '$2 ~ /MIPS_GOTSYM/{print $3}')
213: gotsym2=$(readelf -d $new | awk '$2 ~ /MIPS_GOTSYM/{print $3}')
1.1 guenther 214: fi
215:
216: jump_slots() {
217: case $cpu in
218: hppa*) awk '/IPLT/ && $5 != ""{print $5}' /tmp/r$1
219: ;;
1.4 guenther 220: mips*) # the $((gotsym$1)) converts hex to decimal
221: awk -v g=$((gotsym$1)) \
1.1 guenther 222: '/^Symbol table ..symtab/{exit}
223: $1+0 >= g && $4 == "FUNC" {print $8}' /tmp/s$1
224: ;;
225: *) awk '/JU*MP_SL/ && $5 != ""{print $5}' /tmp/r$1
226: ;;
227: esac | sort -o /tmp/j$1
228: }
229:
230: dynamic_sym() {
231: awk -v s=$1 '/^Symbol table ..symtab/{exit}
232: ! /^ *[1-9]/ {next}
233: $7 == "UND" {print $8 | ("sort -o /tmp/U" s); next }
234: $5 == "GLOBAL" {print $8 | ("sort -o /tmp/DS" s) }
235: $5 == "WEAK" {print $8 | ("sort -o /tmp/DW" s) }
236: $5 != "LOCAL" {print $8 | ("sort -o /tmp/D" s) }
237: {print $4, $5, $6, $8}' /tmp/s$1 | sort -o /tmp/d$1
238: # awk -v s=$1 '$2 == "GLOBAL" {print $4 | ("sort -o /tmp/DS" s) }
239: # $2 == "WEAK" {print $4 | ("sort -o /tmp/DW" s) }
240: # $1 != "SECTION"{print $4}' /tmp/d$1 | sort -o /tmp/D$1
241: }
242:
243: static_sym() {
244: awk '/^Symbol table ..symtab/{s=1}
245: /LOCAL/{next}
246: s&&/^ *[1-9]/{print $4, $5, $6, $8}' /tmp/s$1 | sort -o /tmp/S$1
247: }
248:
249: output_if_not_empty() {
250: leader=$1
251: shift
252: if "$@" | grep -q .
253: then
254: echo "$leader"
255: "$@" | sed 's:^: :'
256: echo
257: fi
258: }
259:
260:
261: for i in 1 2
262: do
263: jump_slots $i
264: dynamic_sym $i
265: static_sym $i
266: comm -23 /tmp/j$i /tmp/U$i >/tmp/J$i
267: done
268:
269: echo "$old --> $new"
270: if cmp -s /tmp/d[12]
271: then
272: printf "No dynamic export changes\n"
273: else
274: printf "Dynamic export changes:\n"
275: output_if_not_empty "added:" comm -13 /tmp/D[12]
276: output_if_not_empty "removed:" comm -23 /tmp/D[12]
277: output_if_not_empty "weakened:" comm -12 /tmp/DS1 /tmp/DW2
278: output_if_not_empty "strengthened:" comm -12 /tmp/DW1 /tmp/DS2
279: fi
280: if ! cmp -s /tmp/U[12]
281: then
282: printf "External reference changes:\n"
283: output_if_not_empty "added:" comm -13 /tmp/U[12]
284: output_if_not_empty "removed:" comm -23 /tmp/U[12]
285: fi
286:
1.5 guenther 287: if $verbose; then
1.1 guenther 288: printf "\nReloc counts:\nbefore:\n"
289: grep ^R /tmp/r1
290: printf "\nafter:\n"
291: grep ^R /tmp/r2
292: fi
293:
294: output_if_not_empty "PLT added:" comm -13 /tmp/J1 /tmp/J2
295: output_if_not_empty "PLT removed:" comm -23 /tmp/J1 /tmp/J2
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