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 a 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 77 #include "extern.h" 78 79 static const char *pname = "crunchide"; 80 81 static void usage(void); 82 83 static void add_to_keep_list(char *symbol); 84 static void add_file_to_keep_list(char *filename); 85 86 static int hide_syms(const char *filename); 87 88 static int verbose; 89 90 int main(int, char *[]); 91 92 int 93 main(int argc, char **argv) 94 { 95 int ch, errors; 96 97 if(argc > 0) pname = argv[0]; 98 99 while ((ch = getopt(argc, argv, "k:f:v")) != -1) 100 switch(ch) { 101 case 'k': 102 add_to_keep_list(optarg); 103 break; 104 case 'f': 105 add_file_to_keep_list(optarg); 106 break; 107 case 'v': 108 verbose = 1; 109 break; 110 default: 111 usage(); 112 } 113 114 argc -= optind; 115 argv += optind; 116 117 if(argc == 0) usage(); 118 119 errors = 0; 120 while(argc) { 121 if (hide_syms(*argv)) 122 errors = 1; 123 argc--, argv++; 124 } 125 126 return errors; 127 } 128 129 static void 130 usage(void) 131 { 132 fprintf(stderr, 133 "usage: %s [-k <symbol-name>] [-f <keep-list-file>] <files> ...\n", 134 pname); 135 exit(1); 136 } 137 138 /* ---------------------------- */ 139 140 static struct keep { 141 struct keep *next; 142 char *sym; 143 } *keep_list; 144 145 static void 146 add_to_keep_list(char *symbol) 147 { 148 struct keep *newp, *prevp, *curp; 149 int cmp; 150 151 cmp = 0; 152 153 for(curp = keep_list, prevp = NULL; curp; prevp = curp, curp = curp->next) 154 if((cmp = strcmp(symbol, curp->sym)) <= 0) break; 155 156 if(curp && cmp == 0) 157 return; /* already in table */ 158 159 newp = (struct keep *) malloc(sizeof(struct keep)); 160 if(newp) newp->sym = strdup(symbol); 161 if(newp == NULL || newp->sym == NULL) { 162 fprintf(stderr, "%s: out of memory for keep list\n", pname); 163 exit(1); 164 } 165 166 newp->next = curp; 167 if(prevp) prevp->next = newp; 168 else keep_list = newp; 169 } 170 171 int 172 in_keep_list(const char *symbol) 173 { 174 struct keep *curp; 175 int cmp; 176 177 cmp = 0; 178 179 for(curp = keep_list; curp; curp = curp->next) 180 if((cmp = strcmp(symbol, curp->sym)) <= 0) break; 181 182 return curp && cmp == 0; 183 } 184 185 static void 186 add_file_to_keep_list(char *filename) 187 { 188 FILE *keepf; 189 char symbol[1024]; 190 int len; 191 192 if((keepf = fopen(filename, "r")) == NULL) { 193 perror(filename); 194 usage(); 195 } 196 197 while(fgets(symbol, sizeof(symbol), keepf)) { 198 len = strlen(symbol); 199 if(len && symbol[len-1] == '\n') 200 symbol[len-1] = '\0'; 201 202 add_to_keep_list(symbol); 203 } 204 fclose(keepf); 205 } 206 207 /* ---------------------------- */ 208 209 static struct { 210 const char *name; 211 int (*check)(int, const char *); /* 1 if match, zero if not */ 212 int (*hide)(int, const char *); /* non-zero if error */ 213 } exec_formats[] = { 214 #ifdef NLIST_ELF32 215 { "ELF32", check_elf32, hide_elf32, }, 216 #endif 217 #ifdef NLIST_ELF64 218 { "ELF64", check_elf64, hide_elf64, }, 219 #endif 220 }; 221 222 static int 223 hide_syms(const char *filename) 224 { 225 int fd, i, n, rv; 226 227 fd = open(filename, O_RDWR, 0); 228 if (fd == -1) { 229 perror(filename); 230 return 1; 231 } 232 233 rv = 0; 234 235 n = sizeof exec_formats / sizeof exec_formats[0]; 236 for (i = 0; i < n; i++) { 237 if (lseek(fd, 0, SEEK_SET) != 0) { 238 perror(filename); 239 goto err; 240 } 241 if ((*exec_formats[i].check)(fd, filename) != 0) 242 break; 243 } 244 if (i == n) { 245 fprintf(stderr, "%s: unknown executable format\n", filename); 246 goto err; 247 } 248 249 if (verbose) 250 fprintf(stderr, "%s is an %s binary\n", filename, 251 exec_formats[i].name); 252 253 if (lseek(fd, 0, SEEK_SET) != 0) { 254 perror(filename); 255 goto err; 256 } 257 rv = (*exec_formats[i].hide)(fd, filename); 258 259 out: 260 close (fd); 261 return (rv); 262 263 err: 264 rv = 1; 265 goto out; 266 } 267