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