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