xref: /freebsd/usr.sbin/crunch/crunchide/crunchide.c (revision 1e413cf93298b5b97441a21d9a50fdcd0ee9945e)
1 /*	$NetBSD: crunchide.c,v 1.8 1997/11/01 06:51:45 lukem Exp $	*/
2 /* $FreeBSD$ */
3 /*
4  * Copyright (c) 1997 Christopher G. Demetriou.  All rights reserved.
5  * Copyright (c) 1994 University of Maryland
6  * All Rights Reserved.
7  *
8  * Permission to use, copy, modify, distribute, and sell this software and its
9  * documentation for any purpose is hereby granted without fee, provided that
10  * the above copyright notice appear in all copies and that both that
11  * copyright notice and this permission notice appear in supporting
12  * documentation, and that the name of U.M. not be used in advertising or
13  * publicity pertaining to distribution of the software without specific,
14  * written prior permission.  U.M. makes no representations about the
15  * suitability of this software for any purpose.  It is provided "as is"
16  * without express or implied warranty.
17  *
18  * U.M. DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL U.M.
20  * BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
21  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
22  * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
23  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
24  *
25  * Author: James da Silva, Systems Design and Analysis Group
26  *			   Computer Science Department
27  *			   University of Maryland at College Park
28  */
29 /*
30  * crunchide.c - tiptoes through an a.out symbol table, hiding all defined
31  *	global symbols.  Allows the user to supply a "keep list" of symbols
32  *	that are not to be hidden.  This program relies on the use of the
33  * 	linker's -dc flag to actually put global bss data into the file's
34  * 	bss segment (rather than leaving it as undefined "common" data).
35  *
36  * 	The point of all this is to allow multiple programs to be linked
37  *	together without getting multiple-defined errors.
38  *
39  *	For example, consider a program "foo.c".  It can be linked with a
40  *	small stub routine, called "foostub.c", eg:
41  *	    int foo_main(int argc, char **argv){ return main(argc, argv); }
42  *      like so:
43  *	    cc -c foo.c foostub.c
44  *	    ld -dc -r foo.o foostub.o -o foo.combined.o
45  *	    crunchide -k _foo_main foo.combined.o
46  *	at this point, foo.combined.o can be linked with another program
47  * 	and invoked with "foo_main(argc, argv)".  foo's main() and any
48  * 	other globals are hidden and will not conflict with other symbols.
49  *
50  * TODO:
51  *	- resolve the theoretical hanging reloc problem (see check_reloc()
52  *	  below). I have yet to see this problem actually occur in any real
53  *	  program. In what cases will gcc/gas generate code that needs a
54  *	  relative reloc from a global symbol, other than PIC?  The
55  *	  solution is to not hide the symbol from the linker in this case,
56  *	  but to generate some random name for it so that it doesn't link
57  *	  with anything but holds the place for the reloc.
58  *      - arrange that all the BSS segments start at the same address, so
59  *	  that the final crunched binary BSS size is the max of all the
60  *	  component programs' BSS sizes, rather than their sum.
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 
67 #include <unistd.h>
68 #include <stdio.h>
69 #include <stdlib.h>
70 #include <string.h>
71 #include <fcntl.h>
72 #include <a.out.h>
73 #include <sys/types.h>
74 #include <sys/stat.h>
75 #include <sys/errno.h>
76 
77 #include "extern.h"
78 
79 char *pname = "crunchide";
80 
81 void usage(void);
82 
83 void add_to_keep_list(char *symbol);
84 void add_file_to_keep_list(char *filename);
85 
86 int hide_syms(const char *filename);
87 
88 int verbose;
89 
90 int main(int, char *[]);
91 
92 int main(argc, argv)
93 int argc;
94 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 {
132     fprintf(stderr,
133 	    "usage: %s [-k <symbol-name>] [-f <keep-list-file>] <files> ...\n",
134 	    pname);
135     exit(1);
136 }
137 
138 /* ---------------------------- */
139 
140 struct keep {
141     struct keep *next;
142     char *sym;
143 } *keep_list;
144 
145 void add_to_keep_list(char *symbol)
146 {
147     struct keep *newp, *prevp, *curp;
148     int cmp;
149 
150     cmp = 0;
151 
152     for(curp = keep_list, prevp = NULL; curp; prevp = curp, curp = curp->next)
153 	if((cmp = strcmp(symbol, curp->sym)) <= 0) break;
154 
155     if(curp && cmp == 0)
156 	return;	/* already in table */
157 
158     newp = (struct keep *) malloc(sizeof(struct keep));
159     if(newp) newp->sym = strdup(symbol);
160     if(newp == NULL || newp->sym == NULL) {
161 	fprintf(stderr, "%s: out of memory for keep list\n", pname);
162 	exit(1);
163     }
164 
165     newp->next = curp;
166     if(prevp) prevp->next = newp;
167     else keep_list = newp;
168 }
169 
170 int in_keep_list(const char *symbol)
171 {
172     struct keep *curp;
173     int cmp;
174 
175     cmp = 0;
176 
177     for(curp = keep_list; curp; curp = curp->next)
178 	if((cmp = strcmp(symbol, curp->sym)) <= 0) break;
179 
180     return curp && cmp == 0;
181 }
182 
183 void add_file_to_keep_list(char *filename)
184 {
185     FILE *keepf;
186     char symbol[1024];
187     int len;
188 
189     if((keepf = fopen(filename, "r")) == NULL) {
190 	perror(filename);
191 	usage();
192     }
193 
194     while(fgets(symbol, sizeof(symbol), keepf)) {
195 	len = strlen(symbol);
196 	if(len && symbol[len-1] == '\n')
197 	    symbol[len-1] = '\0';
198 
199 	add_to_keep_list(symbol);
200     }
201     fclose(keepf);
202 }
203 
204 /* ---------------------------- */
205 
206 struct {
207 	const char *name;
208 	int	(*check)(int, const char *);	/* 1 if match, zero if not */
209 	int	(*hide)(int, const char *);	/* non-zero if error */
210 } exec_formats[] = {
211 #ifdef NLIST_AOUT
212 	{	"a.out",	check_aout,	hide_aout,	},
213 #endif
214 #ifdef NLIST_ECOFF
215 	{	"ECOFF",	check_elf64,	hide_elf64,	},
216 #endif
217 #ifdef NLIST_ELF32
218 	{	"ELF32",	check_elf32,	hide_elf32,	},
219 #endif
220 #ifdef NLIST_ELF64
221 	{	"ELF64",	check_elf64,	hide_elf64,	},
222 #endif
223 };
224 
225 int hide_syms(const char *filename)
226 {
227 	int fd, i, n, rv;
228 
229 	fd = open(filename, O_RDWR, 0);
230 	if (fd == -1) {
231 		perror(filename);
232 		return 1;
233 	}
234 
235 	rv = 0;
236 
237         n = sizeof exec_formats / sizeof exec_formats[0];
238         for (i = 0; i < n; i++) {
239 		if (lseek(fd, 0, SEEK_SET) != 0) {
240 			perror(filename);
241 			goto err;
242 		}
243                 if ((*exec_formats[i].check)(fd, filename) != 0)
244                         break;
245 	}
246 	if (i == n) {
247 		fprintf(stderr, "%s: unknown executable format\n", filename);
248 		goto err;
249 	}
250 
251 	if (verbose)
252 		fprintf(stderr, "%s is an %s binary\n", filename,
253 		    exec_formats[i].name);
254 
255 	if (lseek(fd, 0, SEEK_SET) != 0) {
256 		perror(filename);
257 		goto err;
258 	}
259 	rv = (*exec_formats[i].hide)(fd, filename);
260 
261 out:
262 	close (fd);
263 	return (rv);
264 
265 err:
266 	rv = 1;
267 	goto out;
268 }
269