1 /* $NetBSD: crunchide.c,v 1.8 1997/11/01 06:51:45 lukem 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 /* 29 * crunchide.c - tiptoes through an a.out symbol table, hiding all defined 30 * global symbols. Allows the user to supply a "keep list" of symbols 31 * that are not to be hidden. This program relies on the use of the 32 * linker's -dc flag to actually put global bss data into the file's 33 * bss segment (rather than leaving it as undefined "common" data). 34 * 35 * The point of all this is to allow multiple programs to be linked 36 * together without getting multiple-defined errors. 37 * 38 * For example, consider a program "foo.c". It can be linked with a 39 * small stub routine, called "foostub.c", eg: 40 * int foo_main(int argc, char **argv){ return main(argc, argv); } 41 * like so: 42 * cc -c foo.c foostub.c 43 * ld -dc -r foo.o foostub.o -o foo.combined.o 44 * crunchide -k _foo_main foo.combined.o 45 * at this point, foo.combined.o can be linked with another program 46 * and invoked with "foo_main(argc, argv)". foo's main() and any 47 * other globals are hidden and will not conflict with other symbols. 48 * 49 * TODO: 50 * - resolve the theoretical hanging reloc problem (see check_reloc() 51 * below). I have yet to see this problem actually occur in any real 52 * program. In what cases will gcc/gas generate code that needs a 53 * relative reloc from a global symbol, other than PIC? The 54 * solution is to not hide the symbol from the linker in this case, 55 * but to generate some random name for it so that it doesn't link 56 * with anything but holds the place for the reloc. 57 * - arrange that all the BSS segments start at the same address, so 58 * that the final crunched binary BSS size is the max of all the 59 * component programs' BSS sizes, rather than their sum. 60 */ 61 62 #include <sys/types.h> 63 #include <sys/stat.h> 64 #include <sys/errno.h> 65 #include <unistd.h> 66 #include <stdio.h> 67 #include <stdlib.h> 68 #include <string.h> 69 #include <fcntl.h> 70 #include <a.out.h> 71 72 #include "extern.h" 73 74 char *pname = "crunchide"; 75 76 void usage(void); 77 78 void add_to_keep_list(char *symbol); 79 void add_file_to_keep_list(char *filename); 80 81 int hide_syms(const char *filename); 82 83 int verbose; 84 85 int main(int, char *[]); 86 87 int 88 main(int argc, char **argv) 89 { 90 int ch, errors; 91 92 if(argc > 0) pname = argv[0]; 93 94 while ((ch = getopt(argc, argv, "k:f:v")) != -1) 95 switch(ch) { 96 case 'k': 97 add_to_keep_list(optarg); 98 break; 99 case 'f': 100 add_file_to_keep_list(optarg); 101 break; 102 case 'v': 103 verbose = 1; 104 break; 105 default: 106 usage(); 107 } 108 109 argc -= optind; 110 argv += optind; 111 112 if(argc == 0) usage(); 113 114 errors = 0; 115 while(argc) { 116 if (hide_syms(*argv)) 117 errors = 1; 118 argc--, argv++; 119 } 120 121 return errors; 122 } 123 124 void 125 usage(void) 126 { 127 fprintf(stderr, 128 "usage: %s [-k <symbol-name>] [-f <keep-list-file>] <files> ...\n", 129 pname); 130 exit(1); 131 } 132 133 /* ---------------------------- */ 134 135 struct keep { 136 struct keep *next; 137 char *sym; 138 } *keep_list; 139 140 void 141 add_to_keep_list(char *symbol) 142 { 143 struct keep *newp, *prevp, *curp; 144 int cmp; 145 146 cmp = 0; 147 148 for(curp = keep_list, prevp = NULL; curp; prevp = curp, curp = curp->next) 149 if((cmp = strcmp(symbol, curp->sym)) <= 0) break; 150 151 if(curp && cmp == 0) 152 return; /* already in table */ 153 154 newp = (struct keep *) malloc(sizeof(struct keep)); 155 if(newp) newp->sym = strdup(symbol); 156 if(newp == NULL || newp->sym == NULL) { 157 fprintf(stderr, "%s: out of memory for keep list\n", pname); 158 exit(1); 159 } 160 161 newp->next = curp; 162 if(prevp) prevp->next = newp; 163 else keep_list = newp; 164 } 165 166 int 167 in_keep_list(const char *symbol) 168 { 169 struct keep *curp; 170 int cmp; 171 172 cmp = 0; 173 174 for(curp = keep_list; curp; curp = curp->next) 175 if((cmp = strcmp(symbol, curp->sym)) <= 0) break; 176 177 return curp && cmp == 0; 178 } 179 180 void 181 add_file_to_keep_list(char *filename) 182 { 183 FILE *keepf; 184 char symbol[1024]; 185 int len; 186 187 if((keepf = fopen(filename, "r")) == NULL) { 188 perror(filename); 189 usage(); 190 } 191 192 while(fgets(symbol, sizeof(symbol), keepf)) { 193 len = strlen(symbol); 194 if(len && symbol[len-1] == '\n') 195 symbol[len-1] = '\0'; 196 197 add_to_keep_list(symbol); 198 } 199 fclose(keepf); 200 } 201 202 /* ---------------------------- */ 203 204 struct { 205 const char *name; 206 int (*check)(int, const char *); /* 1 if match, zero if not */ 207 int (*hide)(int, const char *); /* non-zero if error */ 208 } exec_formats[] = { 209 #ifdef NLIST_AOUT 210 { "a.out", check_aout, hide_aout, }, 211 #endif 212 #ifdef NLIST_ECOFF 213 { "ECOFF", check_elf64, hide_elf64, }, 214 #endif 215 #ifdef NLIST_ELF32 216 { "ELF32", check_elf32, hide_elf32, }, 217 #endif 218 #ifdef NLIST_ELF64 219 { "ELF64", check_elf64, hide_elf64, }, 220 #endif 221 }; 222 223 int 224 hide_syms(const char *filename) 225 { 226 int fd, i, n, rv; 227 228 fd = open(filename, O_RDWR, 0); 229 if (fd == -1) { 230 perror(filename); 231 return 1; 232 } 233 234 rv = 0; 235 236 n = sizeof exec_formats / sizeof exec_formats[0]; 237 for (i = 0; i < n; i++) { 238 if (lseek(fd, 0, SEEK_SET) != 0) { 239 perror(filename); 240 goto err; 241 } 242 if ((*exec_formats[i].check)(fd, filename) != 0) 243 break; 244 } 245 if (i == n) { 246 fprintf(stderr, "%s: unknown executable format\n", filename); 247 goto err; 248 } 249 250 if (verbose) 251 fprintf(stderr, "%s is an %s binary\n", filename, 252 exec_formats[i].name); 253 254 if (lseek(fd, 0, SEEK_SET) != 0) { 255 perror(filename); 256 goto err; 257 } 258 rv = (*exec_formats[i].hide)(fd, filename); 259 260 out: 261 close (fd); 262 return (rv); 263 264 err: 265 rv = 1; 266 goto out; 267 } 268