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.  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 
77 #include "extern.h"
78 
79 static const char *pname = "crunchide";
80 
81 static void usage(void);
82 
83 static void add_to_keep_list(char *symbol);
84 static void add_file_to_keep_list(char *filename);
85 
86 static int hide_syms(const char *filename);
87 
88 static int verbose;
89 
90 int main(int, char *[]);
91 
92 int
93 main(int argc, char **argv)
94 {
95     int ch, errors;
96 
97     if(argc > 0) pname = argv[0];
98 
99     while ((ch = getopt(argc, argv, "k:f:v")) != -1)
100 	switch(ch) {
101 	case 'k':
102 	    add_to_keep_list(optarg);
103 	    break;
104 	case 'f':
105 	    add_file_to_keep_list(optarg);
106 	    break;
107 	case 'v':
108 	    verbose = 1;
109 	    break;
110 	default:
111 	    usage();
112 	}
113 
114     argc -= optind;
115     argv += optind;
116 
117     if(argc == 0) usage();
118 
119     errors = 0;
120     while(argc) {
121 	if (hide_syms(*argv))
122 		errors = 1;
123 	argc--, argv++;
124     }
125 
126     return errors;
127 }
128 
129 static void
130 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 static struct keep {
141     struct keep *next;
142     char *sym;
143 } *keep_list;
144 
145 static void
146 add_to_keep_list(char *symbol)
147 {
148     struct keep *newp, *prevp, *curp;
149     int cmp;
150 
151     cmp = 0;
152 
153     for(curp = keep_list, prevp = NULL; curp; prevp = curp, curp = curp->next)
154 	if((cmp = strcmp(symbol, curp->sym)) <= 0) break;
155 
156     if(curp && cmp == 0)
157 	return;	/* already in table */
158 
159     newp = (struct keep *) malloc(sizeof(struct keep));
160     if(newp) newp->sym = strdup(symbol);
161     if(newp == NULL || newp->sym == NULL) {
162 	fprintf(stderr, "%s: out of memory for keep list\n", pname);
163 	exit(1);
164     }
165 
166     newp->next = curp;
167     if(prevp) prevp->next = newp;
168     else keep_list = newp;
169 }
170 
171 int
172 in_keep_list(const char *symbol)
173 {
174     struct keep *curp;
175     int cmp;
176 
177     cmp = 0;
178 
179     for(curp = keep_list; curp; curp = curp->next)
180 	if((cmp = strcmp(symbol, curp->sym)) <= 0) break;
181 
182     return curp && cmp == 0;
183 }
184 
185 static void
186 add_file_to_keep_list(char *filename)
187 {
188     FILE *keepf;
189     char symbol[1024];
190     int len;
191 
192     if((keepf = fopen(filename, "r")) == NULL) {
193 	perror(filename);
194 	usage();
195     }
196 
197     while(fgets(symbol, sizeof(symbol), keepf)) {
198 	len = strlen(symbol);
199 	if(len && symbol[len-1] == '\n')
200 	    symbol[len-1] = '\0';
201 
202 	add_to_keep_list(symbol);
203     }
204     fclose(keepf);
205 }
206 
207 /* ---------------------------- */
208 
209 static struct {
210 	const char *name;
211 	int	(*check)(int, const char *);	/* 1 if match, zero if not */
212 	int	(*hide)(int, const char *);	/* non-zero if error */
213 } exec_formats[] = {
214 #ifdef NLIST_ELF32
215 	{	"ELF32",	check_elf32,	hide_elf32,	},
216 #endif
217 #ifdef NLIST_ELF64
218 	{	"ELF64",	check_elf64,	hide_elf64,	},
219 #endif
220 };
221 
222 static int
223 hide_syms(const char *filename)
224 {
225 	int fd, i, n, rv;
226 
227 	fd = open(filename, O_RDWR, 0);
228 	if (fd == -1) {
229 		perror(filename);
230 		return 1;
231 	}
232 
233 	rv = 0;
234 
235         n = sizeof exec_formats / sizeof exec_formats[0];
236         for (i = 0; i < n; i++) {
237 		if (lseek(fd, 0, SEEK_SET) != 0) {
238 			perror(filename);
239 			goto err;
240 		}
241                 if ((*exec_formats[i].check)(fd, filename) != 0)
242                         break;
243 	}
244 	if (i == n) {
245 		fprintf(stderr, "%s: unknown executable format\n", filename);
246 		goto err;
247 	}
248 
249 	if (verbose)
250 		fprintf(stderr, "%s is an %s binary\n", filename,
251 		    exec_formats[i].name);
252 
253 	if (lseek(fd, 0, SEEK_SET) != 0) {
254 		perror(filename);
255 		goto err;
256 	}
257 	rv = (*exec_formats[i].hide)(fd, filename);
258 
259 out:
260 	close (fd);
261 	return (rv);
262 
263 err:
264 	rv = 1;
265 	goto out;
266 }
267