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/cdefs.h> 63 #ifndef lint 64 __RCSID("$NetBSD: crunchide.c,v 1.8 1997/11/01 06:51:45 lukem Exp $"); 65 #endif 66 __FBSDID("$FreeBSD$"); 67 68 #include <sys/types.h> 69 #include <sys/stat.h> 70 #include <sys/errno.h> 71 #include <unistd.h> 72 #include <stdio.h> 73 #include <stdlib.h> 74 #include <string.h> 75 #include <fcntl.h> 76 #include <a.out.h> 77 78 #include "extern.h" 79 80 char *pname = "crunchide"; 81 82 void usage(void); 83 84 void add_to_keep_list(char *symbol); 85 void add_file_to_keep_list(char *filename); 86 87 int hide_syms(const char *filename); 88 89 int verbose; 90 91 int main(int, char *[]); 92 93 int 94 main(int argc, char **argv) 95 { 96 int ch, errors; 97 98 if(argc > 0) pname = argv[0]; 99 100 while ((ch = getopt(argc, argv, "k:f:v")) != -1) 101 switch(ch) { 102 case 'k': 103 add_to_keep_list(optarg); 104 break; 105 case 'f': 106 add_file_to_keep_list(optarg); 107 break; 108 case 'v': 109 verbose = 1; 110 break; 111 default: 112 usage(); 113 } 114 115 argc -= optind; 116 argv += optind; 117 118 if(argc == 0) usage(); 119 120 errors = 0; 121 while(argc) { 122 if (hide_syms(*argv)) 123 errors = 1; 124 argc--, argv++; 125 } 126 127 return errors; 128 } 129 130 void 131 usage(void) 132 { 133 fprintf(stderr, 134 "usage: %s [-k <symbol-name>] [-f <keep-list-file>] <files> ...\n", 135 pname); 136 exit(1); 137 } 138 139 /* ---------------------------- */ 140 141 struct keep { 142 struct keep *next; 143 char *sym; 144 } *keep_list; 145 146 void 147 add_to_keep_list(char *symbol) 148 { 149 struct keep *newp, *prevp, *curp; 150 int cmp; 151 152 cmp = 0; 153 154 for(curp = keep_list, prevp = NULL; curp; prevp = curp, curp = curp->next) 155 if((cmp = strcmp(symbol, curp->sym)) <= 0) break; 156 157 if(curp && cmp == 0) 158 return; /* already in table */ 159 160 newp = (struct keep *) malloc(sizeof(struct keep)); 161 if(newp) newp->sym = strdup(symbol); 162 if(newp == NULL || newp->sym == NULL) { 163 fprintf(stderr, "%s: out of memory for keep list\n", pname); 164 exit(1); 165 } 166 167 newp->next = curp; 168 if(prevp) prevp->next = newp; 169 else keep_list = newp; 170 } 171 172 int 173 in_keep_list(const char *symbol) 174 { 175 struct keep *curp; 176 int cmp; 177 178 cmp = 0; 179 180 for(curp = keep_list; curp; curp = curp->next) 181 if((cmp = strcmp(symbol, curp->sym)) <= 0) break; 182 183 return curp && cmp == 0; 184 } 185 186 void 187 add_file_to_keep_list(char *filename) 188 { 189 FILE *keepf; 190 char symbol[1024]; 191 int len; 192 193 if((keepf = fopen(filename, "r")) == NULL) { 194 perror(filename); 195 usage(); 196 } 197 198 while(fgets(symbol, sizeof(symbol), keepf)) { 199 len = strlen(symbol); 200 if(len && symbol[len-1] == '\n') 201 symbol[len-1] = '\0'; 202 203 add_to_keep_list(symbol); 204 } 205 fclose(keepf); 206 } 207 208 /* ---------------------------- */ 209 210 struct { 211 const char *name; 212 int (*check)(int, const char *); /* 1 if match, zero if not */ 213 int (*hide)(int, const char *); /* non-zero if error */ 214 } exec_formats[] = { 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