1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
|
#! /usr/bin/perl
# Check that use of symbols declared in a given header does not result
# in any symbols being brought in that are not reserved with external
# linkage for the given standard.
# Copyright (C) 2014 Free Software Foundation, Inc.
# This file is part of the GNU C Library.
# The GNU C Library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
# The GNU C Library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
# You should have received a copy of the GNU Lesser General Public
# License along with the GNU C Library; if not, see
# <http://www.gnu.org/licenses/>.
use GlibcConform;
use Getopt::Long;
GetOptions ('header=s' => \$header, 'standard=s' => \$standard,
'flags=s' => \$flags, 'cc=s' => \$CC, 'tmpdir=s' => \$tmpdir,
'stdsyms=s' => \$stdsyms_file, 'libsyms=s' => \$libsyms_file,
'readelf=s' => \$READELF);
# Load the list of symbols that are OK.
%stdsyms = ();
open (STDSYMS, "<$stdsyms_file") || die ("open $stdsyms_file: $!\n");
while (<STDSYMS>) {
chomp;
$stdsyms{$_} = 1;
}
close (STDSYMS) || die ("close $stdsyms_file: $!\n");
# The following whitelisted symbols are also allowed for now.
#
# * Bug 15421: lgamma wrongly sets signgam for ISO C.
#
# * Bug 17576: stdin, stdout, stderr only reserved with external
# linkage when stdio.h included (and possibly not then), not
# generally.
#
# * False positive: matherr only used conditionally.
#
@whitelist = qw(signgam stdin stdout stderr matherr);
foreach my $sym (@whitelist) {
$stdsyms{$sym} = 1;
}
# Return information about GLOBAL and WEAK symbols listed in readelf
# -s output.
sub list_syms {
my ($syms_file) = @_;
open (SYMS, "<$syms_file") || die ("open $syms_file: $!\n");
my ($file) = $syms_file;
my (@ret) = ();
while (<SYMS>) {
chomp;
if (/^File: (.*)/) {
$file = $1;
$file =~ s|^.*/||;
next;
}
s/^\s*//;
my (@fields) = split (/\s+/, $_);
if (@fields < 8) {
next;
}
my ($bind) = $fields[4];
my ($ndx) = $fields[6];
my ($sym) = $fields[7];
if ($bind ne "GLOBAL" && $bind ne "WEAK") {
next;
}
if ($sym !~ /^\w+$/) {
next;
}
push (@ret, [$file, $sym, $bind, $ndx ne "UND"]);
}
close (SYMS) || die ("close $syms_file: $!\n");
return @ret;
}
# Load information about GLOBAL and WEAK symbols defined or used in
# the standard libraries.
# Strong symbols (defined or undefined) from a given object.
%strong_syms = ();
# Strong undefined symbols from a given object.
%strong_undef_syms = ();
# Objects defining a given symbol (strongly or weakly).
%sym_objs = ();
@sym_data = list_syms ($libsyms_file);
foreach my $sym (@sym_data) {
my ($file, $name, $bind, $defined) = @$sym;
if ($defined) {
if (!defined ($sym_objs{$name})) {
$sym_objs{$name} = [];
}
push (@{$sym_objs{$name}}, $file);
}
if ($bind eq "GLOBAL") {
if (!defined ($strong_syms{$file})) {
$strong_syms{$file} = [];
}
push (@{$strong_syms{$file}}, $name);
if (!$defined) {
if (!defined ($strong_undef_syms{$file})) {
$strong_undef_syms{$file} = [];
}
push (@{$strong_undef_syms{$file}}, $name);
}
}
}
# Determine what ELF-level symbols are brought in by use of C-level
# symbols declared in the given header.
#
# The rules followed are heuristic and so may produce false positives
# and false negatives.
#
# * Weak undefined symbols are ignored; however, if a code path that
# references one (even just to check if its address is 0) is executed,
# that may conflict with a definition of that symbol in the user's
# program.
#
# * Strong undefined symbols are considered of signficance, but it is
# possible that (a) any standard library definition is weak, so can be
# overridden by the user's definition, and (b) the symbol is only used
# conditionally and not if the program is limited to standard
# functionality. (matherr is an example of such a false positive.)
#
# * If a symbol reference is only brought in by the user using a data
# symbol rather than a function from the standard library, this will
# not be detected.
#
# * If a symbol reference is only brought in by crt*.o or libgcc, this
# will not be detected.
#
# * If a symbol reference is only brought in through __builtin_foo in
# a standard macro being compiled to call foo, this will not be
# detected.
#
# * Header inclusions should be compiled several times with different
# options such as -O2, -D_FORTIFY_SOURCE and -D_FILE_OFFSET_BITS=64 to
# find out what symbols are undefined from such a compilation; this is
# not yet implemented.
#
# * This script finds symbols referenced through use of macros on the
# basis that if a macro calls an internal function, that function must
# also be declared in the header. However, the header might also
# declare implementation-namespace functions that are not called by
# any standard macro in the header, resulting in false positives for
# any symbols brought in only through use of those
# implementation-namespace functions.
#
# * Namespace issues can apply for dynamic linking as well as static
# linking, when a call is from one shared library to another or uses a
# PLT entry for a call within a shared library; such issues are only
# detected by this script if the same namespace issue applies for
# static linking.
@c_syms = list_exported_functions ("$CC $flags", $standard, $header, $tmpdir);
$cincfile = "$tmpdir/undef-$$.c";
$cincfile_o = "$tmpdir/undef-$$.o";
$cincfile_sym = "$tmpdir/undef-$$.sym";
open (CINCFILE, ">$cincfile") || die ("open $cincfile: $!\n");
print CINCFILE "#include <$header>\n";
foreach my $sym (sort @c_syms) {
print CINCFILE "void *__glibc_test_$sym = (void *) &$sym;\n";
}
close CINCFILE || die ("close $cincfile: $!\n");
system ("$CC $flags -D_ISOMAC $CFLAGS{$standard} -c $cincfile -o $cincfile_o")
&& die ("compiling failed\n");
system ("LC_ALL=C $READELF -W -s $cincfile_o > $cincfile_sym")
&& die ("readelf failed\n");
@elf_syms = list_syms ($cincfile_sym);
unlink ($cincfile) || die ("unlink $cincfile: $!\n");
unlink ($cincfile_o) || die ("unlink $cincfile_o: $!\n");
unlink ($cincfile_sym) || die ("unlink $cincfile_sym: $!\n");
%strong_seen = ();
%files_seen = ();
%all_undef = ();
%current_undef = ();
foreach my $sym (@elf_syms) {
my ($file, $name, $bind, $defined) = @$sym;
if ($bind eq "GLOBAL" && !$defined) {
$strong_seen{$name} = "[initial] $name";
$all_undef{$name} = "[initial] $name";
$current_undef{$name} = "[initial] $name";
}
}
while (%current_undef) {
%new_undef = ();
foreach my $sym (sort keys %current_undef) {
foreach my $file (@{$sym_objs{$sym}}) {
if (defined ($files_seen{$file})) {
next;
}
$files_seen{$file} = 1;
foreach my $ssym (@{$strong_syms{$file}}) {
if (!defined ($strong_seen{$ssym})) {
$strong_seen{$ssym} = "$current_undef{$sym} -> [$file] $ssym";
}
}
foreach my $usym (@{$strong_undef_syms{$file}}) {
if (!defined ($all_undef{$usym})) {
$all_undef{$usym} = "$current_undef{$sym} -> [$file] $usym";
$new_undef{$usym} = "$current_undef{$sym} -> [$file] $usym";
}
}
}
}
%current_undef = %new_undef;
}
$ret = 0;
foreach my $sym (sort keys %strong_seen) {
if ($sym =~ /^_/) {
next;
}
if (defined ($stdsyms{$sym})) {
next;
}
print "$strong_seen{$sym}\n";
$ret = 1;
}
exit $ret;
|
