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 a 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.
32 *
33 * The point of all this is to allow multiple programs to be linked
34 * together without getting multiple-defined errors.
35 *
36 * For example, consider a program "foo.c". It can be linked with a
37 * small stub routine, called "foostub.c", eg:
38 * int foo_main(int argc, char **argv){ return main(argc, argv); }
39 * like so:
40 * cc -c foo.c foostub.c
41 * ld -r foo.o foostub.o -o foo.combined.o
42 * crunchide -k _foo_main foo.combined.o
43 * at this point, foo.combined.o can be linked with another program
44 * and invoked with "foo_main(argc, argv)". foo's main() and any
45 * other globals are hidden and will not conflict with other symbols.
46 *
47 * TODO:
48 * - resolve the theoretical hanging reloc problem (see check_reloc()
49 * below). I have yet to see this problem actually occur in any real
50 * program. In what cases will gcc/gas generate code that needs a
51 * relative reloc from a global symbol, other than PIC? The
52 * solution is to not hide the symbol from the linker in this case,
53 * but to generate some random name for it so that it doesn't link
54 * with anything but holds the place for the reloc.
55 * - arrange that all the BSS segments start at the same address, so
56 * that the final crunched binary BSS size is the max of all the
57 * component programs' BSS sizes, rather than their sum.
58 */
59
60 #include <sys/cdefs.h>
61 #ifndef lint
62 __RCSID("$NetBSD: crunchide.c,v 1.8 1997/11/01 06:51:45 lukem Exp $");
63 #endif
64 #include <sys/types.h>
65 #include <sys/stat.h>
66 #include <sys/errno.h>
67 #include <unistd.h>
68 #include <stdio.h>
69 #include <stdlib.h>
70 #include <string.h>
71 #include <fcntl.h>
72
73 #include "extern.h"
74
75 static const char *pname = "crunchide";
76
77 static void usage(void) __dead2;
78
79 static void add_to_keep_list(char *symbol);
80 static void add_file_to_keep_list(char *filename);
81
82 static int hide_syms(const char *filename);
83
84 static int verbose;
85
86 int main(int, char *[]);
87
88 int
main(int argc,char ** argv)89 main(int argc, char **argv)
90 {
91 int ch, errors;
92
93 if(argc > 0) pname = argv[0];
94
95 while ((ch = getopt(argc, argv, "k:f:v")) != -1)
96 switch(ch) {
97 case 'k':
98 add_to_keep_list(optarg);
99 break;
100 case 'f':
101 add_file_to_keep_list(optarg);
102 break;
103 case 'v':
104 verbose = 1;
105 break;
106 default:
107 usage();
108 }
109
110 argc -= optind;
111 argv += optind;
112
113 if(argc == 0) usage();
114
115 errors = 0;
116 while(argc) {
117 if (hide_syms(*argv))
118 errors = 1;
119 argc--, argv++;
120 }
121
122 return errors;
123 }
124
125 static void
usage(void)126 usage(void)
127 {
128 fprintf(stderr,
129 "usage: %s [-k <symbol-name>] [-f <keep-list-file>] <files> ...\n",
130 pname);
131 exit(1);
132 }
133
134 /* ---------------------------- */
135
136 static struct keep {
137 struct keep *next;
138 char *sym;
139 } *keep_list;
140
141 static void
add_to_keep_list(char * symbol)142 add_to_keep_list(char *symbol)
143 {
144 struct keep *newp, *prevp, *curp;
145 int cmp;
146
147 cmp = 0;
148
149 for(curp = keep_list, prevp = NULL; curp; prevp = curp, curp = curp->next)
150 if((cmp = strcmp(symbol, curp->sym)) <= 0) break;
151
152 if(curp && cmp == 0)
153 return; /* already in table */
154
155 newp = (struct keep *) malloc(sizeof(struct keep));
156 if(newp) newp->sym = strdup(symbol);
157 if(newp == NULL || newp->sym == NULL) {
158 fprintf(stderr, "%s: out of memory for keep list\n", pname);
159 exit(1);
160 }
161
162 newp->next = curp;
163 if(prevp) prevp->next = newp;
164 else keep_list = newp;
165 }
166
167 int
in_keep_list(const char * symbol)168 in_keep_list(const char *symbol)
169 {
170 struct keep *curp;
171 int cmp;
172
173 cmp = 0;
174
175 for(curp = keep_list; curp; curp = curp->next)
176 if((cmp = strcmp(symbol, curp->sym)) <= 0) break;
177
178 return curp && cmp == 0;
179 }
180
181 static void
add_file_to_keep_list(char * filename)182 add_file_to_keep_list(char *filename)
183 {
184 FILE *keepf;
185 char symbol[1024];
186 int len;
187
188 if((keepf = fopen(filename, "r")) == NULL) {
189 perror(filename);
190 usage();
191 }
192
193 while(fgets(symbol, sizeof(symbol), keepf)) {
194 len = strlen(symbol);
195 if(len && symbol[len-1] == '\n')
196 symbol[len-1] = '\0';
197
198 add_to_keep_list(symbol);
199 }
200 fclose(keepf);
201 }
202
203 /* ---------------------------- */
204
205 static struct {
206 const char *name;
207 int (*check)(int, const char *); /* 1 if match, zero if not */
208 int (*hide)(int, const char *); /* non-zero if error */
209 } exec_formats[] = {
210 #ifdef NLIST_ELF32
211 { "ELF32", check_elf32, hide_elf32, },
212 #endif
213 #ifdef NLIST_ELF64
214 { "ELF64", check_elf64, hide_elf64, },
215 #endif
216 };
217
218 static int
hide_syms(const char * filename)219 hide_syms(const char *filename)
220 {
221 int fd, i, n, rv;
222
223 fd = open(filename, O_RDWR, 0);
224 if (fd == -1) {
225 perror(filename);
226 return 1;
227 }
228
229 rv = 0;
230
231 n = sizeof exec_formats / sizeof exec_formats[0];
232 for (i = 0; i < n; i++) {
233 if (lseek(fd, 0, SEEK_SET) != 0) {
234 perror(filename);
235 goto err;
236 }
237 if ((*exec_formats[i].check)(fd, filename) != 0)
238 break;
239 }
240 if (i == n) {
241 fprintf(stderr, "%s: unknown executable format\n", filename);
242 goto err;
243 }
244
245 if (verbose)
246 fprintf(stderr, "%s is an %s binary\n", filename,
247 exec_formats[i].name);
248
249 if (lseek(fd, 0, SEEK_SET) != 0) {
250 perror(filename);
251 goto err;
252 }
253 rv = (*exec_formats[i].hide)(fd, filename);
254
255 out:
256 close (fd);
257 return (rv);
258
259 err:
260 rv = 1;
261 goto out;
262 }
263