1 /* $NetBSD: crunchide.c,v 1.8 1997/11/01 06:51:45 lukem Exp $ */
2 /*
3 * Copyright (c) 1997 Christopher G. Demetriou. All rights reserved.
4 * Copyright (c) 1994 University of Maryland
5 * All Rights Reserved.
6 *
7 * Permission to use, copy, modify, distribute, and sell this software and its
8 * documentation for any purpose is hereby granted without fee, provided that
9 * the above copyright notice appear in all copies and that both that
10 * copyright notice and this permission notice appear in supporting
11 * documentation, and that the name of U.M. not be used in advertising or
12 * publicity pertaining to distribution of the software without specific,
13 * written prior permission. U.M. makes no representations about the
14 * suitability of this software for any purpose. It is provided "as is"
15 * without express or implied warranty.
16 *
17 * U.M. DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL U.M.
19 * BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
20 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
21 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
22 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
23 *
24 * Author: James da Silva, Systems Design and Analysis Group
25 * Computer Science Department
26 * University of Maryland at College Park
27 */
28 /*
29 * crunchide.c - tiptoes through an a.out symbol table, hiding all defined
30 * global symbols. Allows the user to supply a "keep list" of symbols
31 * that are not to be hidden. This program relies on the use of the
32 * linker's -dc flag to actually put global bss data into the file's
33 * bss segment (rather than leaving it as undefined "common" data).
34 *
35 * The point of all this is to allow multiple programs to be linked
36 * together without getting multiple-defined errors.
37 *
38 * For example, consider a program "foo.c". It can be linked with a
39 * small stub routine, called "foostub.c", eg:
40 * int foo_main(int argc, char **argv){ return main(argc, argv); }
41 * like so:
42 * cc -c foo.c foostub.c
43 * ld -dc -r foo.o foostub.o -o foo.combined.o
44 * crunchide -k _foo_main foo.combined.o
45 * at this point, foo.combined.o can be linked with another program
46 * and invoked with "foo_main(argc, argv)". foo's main() and any
47 * other globals are hidden and will not conflict with other symbols.
48 *
49 * TODO:
50 * - resolve the theoretical hanging reloc problem (see check_reloc()
51 * below). I have yet to see this problem actually occur in any real
52 * program. In what cases will gcc/gas generate code that needs a
53 * relative reloc from a global symbol, other than PIC? The
54 * solution is to not hide the symbol from the linker in this case,
55 * but to generate some random name for it so that it doesn't link
56 * with anything but holds the place for the reloc.
57 * - arrange that all the BSS segments start at the same address, so
58 * that the final crunched binary BSS size is the max of all the
59 * component programs' BSS sizes, rather than their sum.
60 */
61
62 #include <sys/cdefs.h>
63 #ifndef lint
64 __RCSID("$NetBSD: crunchide.c,v 1.8 1997/11/01 06:51:45 lukem Exp $");
65 #endif
66 __FBSDID("$FreeBSD$");
67
68 #include <sys/types.h>
69 #include <sys/stat.h>
70 #include <sys/errno.h>
71 #include <unistd.h>
72 #include <stdio.h>
73 #include <stdlib.h>
74 #include <string.h>
75 #include <fcntl.h>
76 #include <a.out.h>
77
78 #include "extern.h"
79
80 char *pname = "crunchide";
81
82 void usage(void);
83
84 void add_to_keep_list(char *symbol);
85 void add_file_to_keep_list(char *filename);
86
87 int hide_syms(const char *filename);
88
89 int verbose;
90
91 int main(int, char *[]);
92
93 int
main(int argc,char ** argv)94 main(int argc, char **argv)
95 {
96 int ch, errors;
97
98 if(argc > 0) pname = argv[0];
99
100 while ((ch = getopt(argc, argv, "k:f:v")) != -1)
101 switch(ch) {
102 case 'k':
103 add_to_keep_list(optarg);
104 break;
105 case 'f':
106 add_file_to_keep_list(optarg);
107 break;
108 case 'v':
109 verbose = 1;
110 break;
111 default:
112 usage();
113 }
114
115 argc -= optind;
116 argv += optind;
117
118 if(argc == 0) usage();
119
120 errors = 0;
121 while(argc) {
122 if (hide_syms(*argv))
123 errors = 1;
124 argc--, argv++;
125 }
126
127 return errors;
128 }
129
130 void
usage(void)131 usage(void)
132 {
133 fprintf(stderr,
134 "usage: %s [-k <symbol-name>] [-f <keep-list-file>] <files> ...\n",
135 pname);
136 exit(1);
137 }
138
139 /* ---------------------------- */
140
141 struct keep {
142 struct keep *next;
143 char *sym;
144 } *keep_list;
145
146 void
add_to_keep_list(char * symbol)147 add_to_keep_list(char *symbol)
148 {
149 struct keep *newp, *prevp, *curp;
150 int cmp;
151
152 cmp = 0;
153
154 for(curp = keep_list, prevp = NULL; curp; prevp = curp, curp = curp->next)
155 if((cmp = strcmp(symbol, curp->sym)) <= 0) break;
156
157 if(curp && cmp == 0)
158 return; /* already in table */
159
160 newp = (struct keep *) malloc(sizeof(struct keep));
161 if(newp) newp->sym = strdup(symbol);
162 if(newp == NULL || newp->sym == NULL) {
163 fprintf(stderr, "%s: out of memory for keep list\n", pname);
164 exit(1);
165 }
166
167 newp->next = curp;
168 if(prevp) prevp->next = newp;
169 else keep_list = newp;
170 }
171
172 int
in_keep_list(const char * symbol)173 in_keep_list(const char *symbol)
174 {
175 struct keep *curp;
176 int cmp;
177
178 cmp = 0;
179
180 for(curp = keep_list; curp; curp = curp->next)
181 if((cmp = strcmp(symbol, curp->sym)) <= 0) break;
182
183 return curp && cmp == 0;
184 }
185
186 void
add_file_to_keep_list(char * filename)187 add_file_to_keep_list(char *filename)
188 {
189 FILE *keepf;
190 char symbol[1024];
191 int len;
192
193 if((keepf = fopen(filename, "r")) == NULL) {
194 perror(filename);
195 usage();
196 }
197
198 while(fgets(symbol, sizeof(symbol), keepf)) {
199 len = strlen(symbol);
200 if(len && symbol[len-1] == '\n')
201 symbol[len-1] = '\0';
202
203 add_to_keep_list(symbol);
204 }
205 fclose(keepf);
206 }
207
208 /* ---------------------------- */
209
210 struct {
211 const char *name;
212 int (*check)(int, const char *); /* 1 if match, zero if not */
213 int (*hide)(int, const char *); /* non-zero if error */
214 } exec_formats[] = {
215 #ifdef NLIST_ELF32
216 { "ELF32", check_elf32, hide_elf32, },
217 #endif
218 #ifdef NLIST_ELF64
219 { "ELF64", check_elf64, hide_elf64, },
220 #endif
221 };
222
223 int
hide_syms(const char * filename)224 hide_syms(const char *filename)
225 {
226 int fd, i, n, rv;
227
228 fd = open(filename, O_RDWR, 0);
229 if (fd == -1) {
230 perror(filename);
231 return 1;
232 }
233
234 rv = 0;
235
236 n = sizeof exec_formats / sizeof exec_formats[0];
237 for (i = 0; i < n; i++) {
238 if (lseek(fd, 0, SEEK_SET) != 0) {
239 perror(filename);
240 goto err;
241 }
242 if ((*exec_formats[i].check)(fd, filename) != 0)
243 break;
244 }
245 if (i == n) {
246 fprintf(stderr, "%s: unknown executable format\n", filename);
247 goto err;
248 }
249
250 if (verbose)
251 fprintf(stderr, "%s is an %s binary\n", filename,
252 exec_formats[i].name);
253
254 if (lseek(fd, 0, SEEK_SET) != 0) {
255 perror(filename);
256 goto err;
257 }
258 rv = (*exec_formats[i].hide)(fd, filename);
259
260 out:
261 close (fd);
262 return (rv);
263
264 err:
265 rv = 1;
266 goto out;
267 }
268