usr.bin/crunch/crunchide/exec_aout.c

   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
  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
  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
  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
 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) */