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