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 #include <sys/types.h> 65 #include <sys/stat.h> 66 #include <sys/errno.h> 67 #include <unistd.h> 68 #include <stdio.h> 69 #include <stdlib.h> 70 #include <string.h> 71 #include <fcntl.h> 72 73 #include "extern.h" 74 75 static const char *pname = "crunchide"; 76 77 static void usage(void) __dead2; 78 79 static void add_to_keep_list(char *symbol); 80 static void add_file_to_keep_list(char *filename); 81 82 static int hide_syms(const char *filename); 83 84 static int verbose; 85 86 int main(int, char *[]); 87 88 int 89 main(int argc, char **argv) 90 { 91 int ch, errors; 92 93 if(argc > 0) pname = argv[0]; 94 95 while ((ch = getopt(argc, argv, "k:f:v")) != -1) 96 switch(ch) { 97 case 'k': 98 add_to_keep_list(optarg); 99 break; 100 case 'f': 101 add_file_to_keep_list(optarg); 102 break; 103 case 'v': 104 verbose = 1; 105 break; 106 default: 107 usage(); 108 } 109 110 argc -= optind; 111 argv += optind; 112 113 if(argc == 0) usage(); 114 115 errors = 0; 116 while(argc) { 117 if (hide_syms(*argv)) 118 errors = 1; 119 argc--, argv++; 120 } 121 122 return errors; 123 } 124 125 static void 126 usage(void) 127 { 128 fprintf(stderr, 129 "usage: %s [-k <symbol-name>] [-f <keep-list-file>] <files> ...\n", 130 pname); 131 exit(1); 132 } 133 134 /* ---------------------------- */ 135 136 static struct keep { 137 struct keep *next; 138 char *sym; 139 } *keep_list; 140 141 static void 142 add_to_keep_list(char *symbol) 143 { 144 struct keep *newp, *prevp, *curp; 145 int cmp; 146 147 cmp = 0; 148 149 for(curp = keep_list, prevp = NULL; curp; prevp = curp, curp = curp->next) 150 if((cmp = strcmp(symbol, curp->sym)) <= 0) break; 151 152 if(curp && cmp == 0) 153 return; /* already in table */ 154 155 newp = (struct keep *) malloc(sizeof(struct keep)); 156 if(newp) newp->sym = strdup(symbol); 157 if(newp == NULL || newp->sym == NULL) { 158 fprintf(stderr, "%s: out of memory for keep list\n", pname); 159 exit(1); 160 } 161 162 newp->next = curp; 163 if(prevp) prevp->next = newp; 164 else keep_list = newp; 165 } 166 167 int 168 in_keep_list(const char *symbol) 169 { 170 struct keep *curp; 171 int cmp; 172 173 cmp = 0; 174 175 for(curp = keep_list; curp; curp = curp->next) 176 if((cmp = strcmp(symbol, curp->sym)) <= 0) break; 177 178 return curp && cmp == 0; 179 } 180 181 static void 182 add_file_to_keep_list(char *filename) 183 { 184 FILE *keepf; 185 char symbol[1024]; 186 int len; 187 188 if((keepf = fopen(filename, "r")) == NULL) { 189 perror(filename); 190 usage(); 191 } 192 193 while(fgets(symbol, sizeof(symbol), keepf)) { 194 len = strlen(symbol); 195 if(len && symbol[len-1] == '\n') 196 symbol[len-1] = '\0'; 197 198 add_to_keep_list(symbol); 199 } 200 fclose(keepf); 201 } 202 203 /* ---------------------------- */ 204 205 static struct { 206 const char *name; 207 int (*check)(int, const char *); /* 1 if match, zero if not */ 208 int (*hide)(int, const char *); /* non-zero if error */ 209 } exec_formats[] = { 210 #ifdef NLIST_ELF32 211 { "ELF32", check_elf32, hide_elf32, }, 212 #endif 213 #ifdef NLIST_ELF64 214 { "ELF64", check_elf64, hide_elf64, }, 215 #endif 216 }; 217 218 static int 219 hide_syms(const char *filename) 220 { 221 int fd, i, n, rv; 222 223 fd = open(filename, O_RDWR, 0); 224 if (fd == -1) { 225 perror(filename); 226 return 1; 227 } 228 229 rv = 0; 230 231 n = sizeof exec_formats / sizeof exec_formats[0]; 232 for (i = 0; i < n; i++) { 233 if (lseek(fd, 0, SEEK_SET) != 0) { 234 perror(filename); 235 goto err; 236 } 237 if ((*exec_formats[i].check)(fd, filename) != 0) 238 break; 239 } 240 if (i == n) { 241 fprintf(stderr, "%s: unknown executable format\n", filename); 242 goto err; 243 } 244 245 if (verbose) 246 fprintf(stderr, "%s is an %s binary\n", filename, 247 exec_formats[i].name); 248 249 if (lseek(fd, 0, SEEK_SET) != 0) { 250 perror(filename); 251 goto err; 252 } 253 rv = (*exec_formats[i].hide)(fd, filename); 254 255 out: 256 close (fd); 257 return (rv); 258 259 err: 260 rv = 1; 261 goto out; 262 } 263