1 /* $NetBSD: exec_aout.c,v 1.6 1997/08/02 21:30:17 perry 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 #include <sys/cdefs.h> 29 #ifndef lint 30 __RCSID("$NetBSD: exec_aout.c,v 1.6 1997/08/02 21:30:17 perry Exp $"); 31 #endif 32 33 #include <unistd.h> 34 #include <stdio.h> 35 #include <stdlib.h> 36 #include <string.h> 37 #include <a.out.h> 38 #include <sys/types.h> 39 #include <sys/stat.h> 40 #include <sys/errno.h> 41 42 #include "extern.h" 43 44 #if defined(NLIST_AOUT) 45 46 int nsyms, ntextrel, ndatarel; 47 struct exec *hdrp; 48 char *aoutdata, *strbase; 49 struct relocation_info *textrel, *datarel; 50 struct nlist *symbase; 51 52 53 #define SYMSTR(sp) (&strbase[(sp)->n_un.n_strx]) 54 55 /* is the symbol a global symbol defined in the current file? */ 56 #define IS_GLOBAL_DEFINED(sp) \ 57 (((sp)->n_type & N_EXT) && ((sp)->n_type & N_TYPE) != N_UNDF) 58 59 #ifdef __sparc 60 /* is the relocation entry dependent on a symbol? */ 61 #define IS_SYMBOL_RELOC(rp) \ 62 ((rp)->r_extern || \ 63 ((rp)->r_type >= RELOC_BASE10 && (rp)->r_type <= RELOC_BASE22) || \ 64 (rp)->r_type == RELOC_JMP_TBL) 65 #else 66 /* is the relocation entry dependent on a symbol? */ 67 #define IS_SYMBOL_RELOC(rp) \ 68 ((rp)->r_extern||(rp)->r_baserel||(rp)->r_jmptable) 69 #endif 70 71 static void check_reloc(const char *filename, struct relocation_info *relp); 72 73 int check_aout(int inf, const char *filename) 74 { 75 struct stat infstat; 76 struct exec eh; 77 78 /* 79 * check the header to make sure it's an a.out-format file. 80 */ 81 82 if(fstat(inf, &infstat) == -1) 83 return 0; 84 if(infstat.st_size < sizeof eh) 85 return 0; 86 if(read(inf, &eh, sizeof eh) != sizeof eh) 87 return 0; 88 89 if(N_BADMAG(eh)) 90 return 0; 91 92 return 1; 93 } 94 95 int hide_aout(int inf, const char *filename) 96 { 97 struct stat infstat; 98 struct relocation_info *relp; 99 struct nlist *symp; 100 int rc; 101 102 /* 103 * do some error checking. 104 */ 105 106 if(fstat(inf, &infstat) == -1) { 107 perror(filename); 108 return 1; 109 } 110 111 /* 112 * Read the entire file into memory. XXX - Really, we only need to 113 * read the header and from TRELOFF to the end of the file. 114 */ 115 116 if((aoutdata = (char *) malloc(infstat.st_size)) == NULL) { 117 fprintf(stderr, "%s: too big to read into memory\n", filename); 118 return 1; 119 } 120 121 if((rc = read(inf, aoutdata, infstat.st_size)) < infstat.st_size) { 122 fprintf(stderr, "%s: read error: %s\n", filename, 123 rc == -1? strerror(errno) : "short read"); 124 return 1; 125 } 126 127 /* 128 * Calculate offsets and sizes from the header. 129 */ 130 131 hdrp = (struct exec *) aoutdata; 132 133 #ifdef __FreeBSD__ 134 textrel = (struct relocation_info *) (aoutdata + N_RELOFF(*hdrp)); 135 datarel = (struct relocation_info *) (aoutdata + N_RELOFF(*hdrp) + 136 hdrp->a_trsize); 137 #else 138 textrel = (struct relocation_info *) (aoutdata + N_TRELOFF(*hdrp)); 139 datarel = (struct relocation_info *) (aoutdata + N_DRELOFF(*hdrp)); 140 #endif 141 symbase = (struct nlist *) (aoutdata + N_SYMOFF(*hdrp)); 142 strbase = (char *) (aoutdata + N_STROFF(*hdrp)); 143 144 ntextrel = hdrp->a_trsize / sizeof(struct relocation_info); 145 ndatarel = hdrp->a_drsize / sizeof(struct relocation_info); 146 nsyms = hdrp->a_syms / sizeof(struct nlist); 147 148 /* 149 * Zap the type field of all globally-defined symbols. The linker will 150 * subsequently ignore these entries. Don't zap any symbols in the 151 * keep list. 152 */ 153 154 for(symp = symbase; symp < symbase + nsyms; symp++) { 155 if(!IS_GLOBAL_DEFINED(symp)) /* keep undefined syms */ 156 continue; 157 158 /* keep (C) symbols which are on the keep list */ 159 if(SYMSTR(symp)[0] == '_' && in_keep_list(SYMSTR(symp) + 1)) 160 continue; 161 162 symp->n_type = 0; 163 } 164 165 /* 166 * Check whether the relocation entries reference any symbols that we 167 * just zapped. I don't know whether ld can handle this case, but I 168 * haven't encountered it yet. These checks are here so that the program 169 * doesn't fail silently should such symbols be encountered. 170 */ 171 172 for(relp = textrel; relp < textrel + ntextrel; relp++) 173 check_reloc(filename, relp); 174 for(relp = datarel; relp < datarel + ndatarel; relp++) 175 check_reloc(filename, relp); 176 177 /* 178 * Write the .o file back out to disk. XXX - Really, we only need to 179 * write the symbol table entries back out. 180 */ 181 lseek(inf, 0, SEEK_SET); 182 if((rc = write(inf, aoutdata, infstat.st_size)) < infstat.st_size) { 183 fprintf(stderr, "%s: write error: %s\n", filename, 184 rc == -1? strerror(errno) : "short write"); 185 return 1; 186 } 187 188 return 0; 189 } 190 191 192 static void check_reloc(const char *filename, struct relocation_info *relp) 193 { 194 /* bail out if we zapped a symbol that is needed */ 195 if(IS_SYMBOL_RELOC(relp) && symbase[relp->r_symbolnum].n_type == 0) { 196 fprintf(stderr, 197 "%s: oops, have hanging relocation for %s: bailing out!\n", 198 filename, SYMSTR(&symbase[relp->r_symbolnum])); 199 exit(1); 200 } 201 } 202 203 #endif /* defined(NLIST_AOUT) */ 204