1/* $NetBSD: exec_aout.c,v 1.11 2009/08/16 18:15:28 martin 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 1.11 2009/08/16 18:15:28 martin 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
50int nsyms, ntextrel, ndatarel;
51struct exec *hdrp;
52char *aoutdata, *strbase;
53struct relocation_info *textrel, *datarel;
54struct 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
75static void check_reloc(const char *filename, struct relocation_info *relp);
76
77int 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
99int 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
196static 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