usr.bin/crunch/crunchide/crunchide.c

   1 /* $NetBSD: crunchide.c,v 1.12 2004/08/24 12:25:26 wiz Exp $ */
   2
   3 /*
   4  * Copyright (c) 1997 Christopher G. Demetriou.  All rights reserved.
   5  * Copyright (c) 1994 University of Maryland
   6  * All Rights Reserved.
   7  *
   8  * Permission to use, copy, modify, distribute, and sell this software and its
   9  * documentation for any purpose is hereby granted without fee, provided that
  10  * the above copyright notice appear in all copies and that both that
  11  * copyright notice and this permission notice appear in supporting
  12  * documentation, and that the name of U.M. not be used in advertising or
  13  * publicity pertaining to distribution of the software without specific,
  14  * written prior permission.  U.M. makes no representations about the
  15  * suitability of this software for any purpose.  It is provided "as is"
  16  * without express or implied warranty.
  17  *
  18  * U.M. DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL U.M.
  20  * BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  21  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
  22  * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
  23  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  24  *
  25  * Author: James da Silva, Systems Design and Analysis Group
  26  *                         Computer Science Department
  27  *                         University of Maryland at College Park
  28  */
  29
  30 /*
  31  * crunchide.c - tiptoes through a symbol table, hiding all defined
  32  *      global symbols.  Allows the user to supply a "keep list" of symbols
  33  *      that are not to be hidden.  This program relies on the use of the
  34  *      linker's -dc flag to actually put global bss data into the file's
  35  *      bss segment (rather than leaving it as undefined "common" data).
  36  *
  37  *      The point of all this is to allow multiple programs to be linked
  38  *      together without getting multiple-defined errors.
  39  *
  40  *      For example, consider a program "foo.c".  It can be linked with a
  41  *      small stub routine, called "foostub.c", eg:
  42  *          int foo_main(int argc, char **argv){ return main(argc, argv); }
  43  *      like so:
  44  *          cc -c foo.c foostub.c
  45  *          ld -dc -r foo.o foostub.o -o foo.combined.o
  46  *          crunchide -k _foo_main foo.combined.o
  47  *      at this point, foo.combined.o can be linked with another program
  48  *      and invoked with "foo_main(argc, argv)".  foo's main() and any
  49  *      other globals are hidden and will not conflict with other symbols.
  50  *
  51  * TODO:
  52  *      - resolve the theoretical hanging reloc problem (see check_reloc()
  53  *        below). I have yet to see this problem actually occur in any real
  54  *        program. In what cases will gcc/gas generate code that needs a
  55  *        relative reloc from a global symbol, other than PIC?  The
  56  *        solution is to not hide the symbol from the linker in this case,
  57  *        but to generate some random name for it so that it doesn't link
  58  *        with anything but holds the place for the reloc.
  59  *      - arrange that all the BSS segments start at the same address, so
  60  *        that the final crunched binary BSS size is the max of all the
  61  *        component programs' BSS sizes, rather than their sum.
  62  */
  63
  64 #include <sys/cdefs.h>
  65 #ifndef lint
  66 __RCSID("$NetBSD: crunchide.c,v 1.12 2004/08/24 12:25:26 wiz Exp $");
  67 #endif
  68
  69 #include <unistd.h>
  70 #include <stdio.h>
  71 #include <stdlib.h>
  72 #include <string.h>
  73 #include <fcntl.h>
  74 #include <errno.h>
  75 #include <sys/types.h>
  76 #include <sys/stat.h>
  77
  78 #include "extern.h"
  79
  80 void usage(void);
  81
  82 void add_to_keep_list(char *symbol);
  83 void add_file_to_keep_list(char *filename);
  84
  85 int hide_syms(const char *filename);
  86
  87 int verbose;
  88
  89 int
  90 main(int argc, char *argv[])
  91 {
  92         int ch, errors;
  93
  94         setprogname(argv[0]);
  95
  96         while ((ch = getopt(argc, argv, "k:f:v")) != -1)
  97                 switch(ch) {
  98                 case 'k':
  99                         add_to_keep_list(optarg);
 100                         break;
 101                 case 'f':
 102                         add_file_to_keep_list(optarg);
 103                         break;
 104                 case 'v':
 105                         verbose = 1;
 106                         break;
 107                 default:
 108                         usage();
 109                 }
 110
 111         argc -= optind;
 112         argv += optind;
 113
 114         if (argc == 0)
 115                 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 void
 128 usage(void)
 129 {
 130         fprintf(stderr,
 131                 "Usage: %s [-k keep-symbol] [-f keep-list-file] object-file\n"
 132                 "\t\t [object-file ...]\n",
 133                 getprogname());
 134         exit(1);
 135 }
 136
 137 /* ---------------------------- */
 138
 139 struct keep {
 140         struct keep *next;
 141         char *sym;
 142 } *keep_list;
 143
 144 void
 145 add_to_keep_list(char *symbol)
 146 {
 147         struct keep *newp, *prevp, *curp;
 148         int cmp;
 149
 150         cmp = 0;
 151
 152         for (curp = keep_list, prevp = NULL; curp; prevp = curp, curp = curp->next)
 153                 if ((cmp = strcmp(symbol, curp->sym)) <= 0)
 154                         break;
 155
 156         if (curp && cmp == 0)
 157                 return; /* already in table */
 158
 159         newp = (struct keep *) malloc(sizeof(struct keep));
 160         if (newp)
 161                 newp->sym = strdup(symbol);
 162         if (newp == NULL || newp->sym == NULL) {
 163                 fprintf(stderr, "%s: out of memory for keep list\n", getprogname());
 164                 exit(1);
 165         }
 166
 167         newp->next = curp;
 168         if (prevp)
 169                 prevp->next = newp;
 170         else
 171                 keep_list = newp;
 172 }
 173
 174 int
 175 in_keep_list(const char *symbol)
 176 {
 177         struct keep *curp;
 178         int cmp;
 179
 180         cmp = 0;
 181
 182         for (curp = keep_list; curp; curp = curp->next)
 183                 if((cmp = strcmp(symbol, curp->sym)) <= 0)
 184                         break;
 185
 186         return curp && cmp == 0;
 187 }
 188
 189 void
 190 add_file_to_keep_list(char *filename)
 191 {
 192         FILE *keepf;
 193         char symbol[1024];
 194         int len;
 195
 196         if ((keepf = fopen(filename, "r")) == NULL) {
 197                 perror(filename);
 198                 usage();
 199         }
 200
 201         while (fgets(symbol, 1024, keepf)) {
 202                 len = strlen(symbol);
 203                 if (len && symbol[len-1] == '\n')
 204                         symbol[len-1] = '\0';
 205
 206                 add_to_keep_list(symbol);
 207         }
 208         fclose(keepf);
 209 }
 210
 211 /* ---------------------------- */
 212
 213 struct {
 214         const char *name;
 215         int     (*check)(int, const char *);    /* 1 if match, zero if not */
 216         int     (*hide)(int, const char *);     /* non-zero if error */
 217 } exec_formats[] = {
 218 #ifdef NLIST_AOUT
 219         {       "a.out",        check_aout,     hide_aout,      },
 220 #endif
 221 #ifdef NLIST_COFF
 222         {       "COFF",         check_coff,     hide_coff,      },
 223 #endif
 224 #ifdef NLIST_ECOFF
 225         {       "ECOFF",        check_ecoff,    hide_ecoff,     },
 226 #endif
 227 #ifdef NLIST_ELF32
 228         {       "ELF32",        check_elf32,    hide_elf32,     },
 229 #endif
 230 #ifdef NLIST_ELF64
 231         {       "ELF64",        check_elf64,    hide_elf64,     },
 232 #endif
 233 };
 234
 235 int
 236 hide_syms(const char *filename)
 237 {
 238         int fd, i, n, rv;
 239
 240         fd = open(filename, O_RDWR, 0);
 241         if (fd == -1) {
 242                 perror(filename);
 243                 return 1;
 244         }
 245
 246         rv = 0;
 247
 248         n = sizeof exec_formats / sizeof exec_formats[0];
 249         for (i = 0; i < n; i++) {
 250                 if (lseek(fd, 0, SEEK_SET) != 0) {
 251                         perror(filename);
 252                         goto err;
 253                 }
 254                 if ((*exec_formats[i].check)(fd, filename) != 0)
 255                         break;
 256         }
 257         if (i == n) {
 258                 fprintf(stderr, "%s: unknown executable format\n", filename);
 259                 goto err;
 260         }
 261
 262         if (verbose)
 263                 fprintf(stderr, "%s is an %s binary\n", filename,
 264                     exec_formats[i].name);
 265
 266         if (lseek(fd, 0, SEEK_SET) != 0) {
 267                 perror(filename);
 268                 goto err;
 269         }
 270         rv = (*exec_formats[i].hide)(fd, filename);
 271
 272 out:
 273         close(fd);
 274         return rv;
 275
 276 err:
 277         rv = 1;
 278         goto out;
 279 }