1 /* $NetBSD: exec_aout.c,v 1.12 2009/08/20 17:40:26 he Exp $ */
2
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 #include <sys/cdefs.h>
31 #ifndef lint
32 __RCSID("$NetBSD: exec_aout.c,v 1.12 2009/08/20 17:40:26 he Exp $");
33 #endif
34
35 #include <unistd.h>
36 #include <stdio.h>
37 #include <stdlib.h>
38 #include <string.h>
39 #include <errno.h>
40 #include <sys/types.h>
41 #include <sys/stat.h>
42
43 #include "extern.h"
44
45 #if defined(NLIST_AOUT)
46
47 #include <a.out.h>
48 #include <sys/exec_aout.h>
49
50 int nsyms, ntextrel, ndatarel;
51 struct exec *hdrp;
52 char *aoutdata, *strbase;
53 struct relocation_info *textrel, *datarel;
54 struct nlist *symbase;
55
56
57 #define SYMSTR(sp) (&strbase[(sp)->n_un.n_strx])
58
59 /* is the symbol a global symbol defined in the current file? */
60 #define IS_GLOBAL_DEFINED(sp) \
61 (((sp)->n_type & N_EXT) && ((sp)->n_type & N_TYPE) != N_UNDF)
62
63 #ifdef __sparc__
64 /* is the relocation entry dependent on a symbol? */
65 #define IS_SYMBOL_RELOC(rp) \
66 ((rp)->r_extern || \
67 ((rp)->r_type >= RELOC_BASE10 && (rp)->r_type <= RELOC_BASE22) || \
68 (rp)->r_type == RELOC_JMP_TBL)
69 #else
70 /* is the relocation entry dependent on a symbol? */
71 #define IS_SYMBOL_RELOC(rp) \
72 ((rp)->r_extern||(rp)->r_baserel||(rp)->r_jmptable)
73 #endif
74
75 static void check_reloc(const char *filename, struct relocation_info *relp);
76
check_aout(int inf,const char * filename)77 int check_aout(int inf, const char *filename)
78 {
79 struct stat infstat;
80 struct exec eh;
81
82 /*
83 * check the header to make sure it's an a.out-format file.
84 */
85
86 if(fstat(inf, &infstat) == -1)
87 return 0;
88 if(infstat.st_size < (ssize_t)sizeof eh)
89 return 0;
90 if(read(inf, &eh, sizeof eh) != sizeof eh)
91 return 0;
92
93 if(N_BADMAG(eh))
94 return 0;
95
96 return 1;
97 }
98
hide_aout(int inf,const char * filename)99 int hide_aout(int inf, const char *filename)
100 {
101 struct stat infstat;
102 struct relocation_info *relp;
103 struct nlist *symp;
104 int rc;
105
106 /*
107 * do some error checking.
108 */
109
110 if(fstat(inf, &infstat) == -1) {
111 perror(filename);
112 return 1;
113 }
114
115 /*
116 * Read the entire file into memory. XXX - Really, we only need to
117 * read the header and from TRELOFF to the end of the file.
118 */
119
120 if((aoutdata = (char *) malloc(infstat.st_size)) == NULL) {
121 fprintf(stderr, "%s: too big to read into memory\n", filename);
122 return 1;
123 }
124
125 if((rc = read(inf, aoutdata, infstat.st_size)) < infstat.st_size) {
126 fprintf(stderr, "%s: read error: %s\n", filename,
127 rc == -1? strerror(errno) : "short read");
128 return 1;
129 }
130
131 /*
132 * Calculate offsets and sizes from the header.
133 */
134
135 hdrp = (struct exec *) aoutdata;
136
137 #ifdef __FreeBSD__
138 textrel = (struct relocation_info *) (aoutdata + N_RELOFF(*hdrp));
139 datarel = (struct relocation_info *) (aoutdata + N_RELOFF(*hdrp) +
140 hdrp->a_trsize);
141 #else
142 textrel = (struct relocation_info *) (aoutdata + N_TRELOFF(*hdrp));
143 datarel = (struct relocation_info *) (aoutdata + N_DRELOFF(*hdrp));
144 #endif
145 symbase = (struct nlist *) (aoutdata + N_SYMOFF(*hdrp));
146 strbase = (char *) (aoutdata + N_STROFF(*hdrp));
147
148 ntextrel = hdrp->a_trsize / sizeof(struct relocation_info);
149 ndatarel = hdrp->a_drsize / sizeof(struct relocation_info);
150 nsyms = hdrp->a_syms / sizeof(struct nlist);
151
152 /*
153 * Zap the type field of all globally-defined symbols. The linker will
154 * subsequently ignore these entries. Don't zap any symbols in the
155 * keep list.
156 */
157
158 for(symp = symbase; symp < symbase + nsyms; symp++) {
159 if(!IS_GLOBAL_DEFINED(symp)) /* keep undefined syms */
160 continue;
161
162 /* keep (C) symbols which are on the keep list */
163 if(SYMSTR(symp)[0] == '_' && in_keep_list(SYMSTR(symp) + 1))
164 continue;
165
166 symp->n_type = 0;
167 }
168
169 /*
170 * Check whether the relocation entries reference any symbols that we
171 * just zapped. I don't know whether ld can handle this case, but I
172 * haven't encountered it yet. These checks are here so that the program
173 * doesn't fail silently should such symbols be encountered.
174 */
175
176 for(relp = textrel; relp < textrel + ntextrel; relp++)
177 check_reloc(filename, relp);
178 for(relp = datarel; relp < datarel + ndatarel; relp++)
179 check_reloc(filename, relp);
180
181 /*
182 * Write the .o file back out to disk. XXX - Really, we only need to
183 * write the symbol table entries back out.
184 */
185 lseek(inf, 0, SEEK_SET);
186 if((rc = write(inf, aoutdata, infstat.st_size)) < infstat.st_size) {
187 fprintf(stderr, "%s: write error: %s\n", filename,
188 rc == -1? strerror(errno) : "short write");
189 return 1;
190 }
191
192 return 0;
193 }
194
195
check_reloc(const char * filename,struct relocation_info * relp)196 static void check_reloc(const char *filename, struct relocation_info *relp)
197 {
198 /* bail out if we zapped a symbol that is needed */
199 if(IS_SYMBOL_RELOC(relp) && symbase[relp->r_symbolnum].n_type == 0) {
200 fprintf(stderr,
201 "%s: oops, have hanging relocation for %s: bailing out!\n",
202 filename, SYMSTR(&symbase[relp->r_symbolnum]));
203 exit(1);
204 }
205 }
206
207 #endif /* defined(NLIST_AOUT) */
208