usr.sbin/crunch/crunchide/crunchide.c

   1 /*      $NetBSD: crunchide.c,v 1.8 1997/11/01 06:51:45 lukem Exp $      */
   2 /* $FreeBSD$ */
   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  * crunchide.c - tiptoes through an a.out symbol table, hiding all defined
  31  *      global symbols.  Allows the user to supply a "keep list" of symbols
  32  *      that are not to be hidden.  This program relies on the use of the
  33  *      linker's -dc flag to actually put global bss data into the file's
  34  *      bss segment (rather than leaving it as undefined "common" data).
  35  *
  36  *      The point of all this is to allow multiple programs to be linked
  37  *      together without getting multiple-defined errors.
  38  *
  39  *      For example, consider a program "foo.c".  It can be linked with a
  40  *      small stub routine, called "foostub.c", eg:
  41  *          int foo_main(int argc, char **argv){ return main(argc, argv); }
  42  *      like so:
  43  *          cc -c foo.c foostub.c
  44  *          ld -dc -r foo.o foostub.o -o foo.combined.o
  45  *          crunchide -k _foo_main foo.combined.o
  46  *      at this point, foo.combined.o can be linked with another program
  47  *      and invoked with "foo_main(argc, argv)".  foo's main() and any
  48  *      other globals are hidden and will not conflict with other symbols.
  49  *
  50  * TODO:
  51  *      - resolve the theoretical hanging reloc problem (see check_reloc()
  52  *        below). I have yet to see this problem actually occur in any real
  53  *        program. In what cases will gcc/gas generate code that needs a
  54  *        relative reloc from a global symbol, other than PIC?  The
  55  *        solution is to not hide the symbol from the linker in this case,
  56  *        but to generate some random name for it so that it doesn't link
  57  *        with anything but holds the place for the reloc.
  58  *      - arrange that all the BSS segments start at the same address, so
  59  *        that the final crunched binary BSS size is the max of all the
  60  *        component programs' BSS sizes, rather than their sum.
  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
  67 #include <unistd.h>
  68 #include <stdio.h>
  69 #include <stdlib.h>
  70 #include <string.h>
  71 #include <fcntl.h>
  72 #include <a.out.h>
  73 #include <sys/types.h>
  74 #include <sys/stat.h>
  75 #include <sys/errno.h>
  76
  77 #include "extern.h"
  78
  79 char *pname = "crunchide";
  80
  81 void usage(void);
  82
  83 void add_to_keep_list(char *symbol);
  84 void add_file_to_keep_list(char *filename);
  85
  86 int hide_syms(const char *filename);
  87
  88 int verbose;
  89
  90 int main(int, char *[]);
  91
  92 int main(argc, argv)
  93 int argc;
  94 char **argv;
  95 {
  96     int ch, errors;
  97
  98     if(argc > 0) pname = argv[0];
  99
 100     while ((ch = getopt(argc, argv, "k:f:v")) != -1)
 101         switch(ch) {
 102         case 'k':
 103             add_to_keep_list(optarg);
 104             break;
 105         case 'f':
 106             add_file_to_keep_list(optarg);
 107             break;
 108         case 'v':
 109             verbose = 1;
 110             break;
 111         default:
 112             usage();
 113         }
 114
 115     argc -= optind;
 116     argv += optind;
 117
 118     if(argc == 0) usage();
 119
 120     errors = 0;
 121     while(argc) {
 122         if (hide_syms(*argv))
 123                 errors = 1;
 124         argc--, argv++;
 125     }
 126
 127     return errors;
 128 }
 129
 130 void 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 struct keep {
 141     struct keep *next;
 142     char *sym;
 143 } *keep_list;
 144
 145 void 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) break;
 154
 155     if(curp && cmp == 0)
 156         return; /* already in table */
 157
 158     newp = (struct keep *) malloc(sizeof(struct keep));
 159     if(newp) newp->sym = strdup(symbol);
 160     if(newp == NULL || newp->sym == NULL) {
 161         fprintf(stderr, "%s: out of memory for keep list\n", pname);
 162         exit(1);
 163     }
 164
 165     newp->next = curp;
 166     if(prevp) prevp->next = newp;
 167     else keep_list = newp;
 168 }
 169
 170 int 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 void add_file_to_keep_list(char *filename)
 184 {
 185     FILE *keepf;
 186     char symbol[1024];
 187     int len;
 188
 189     if((keepf = fopen(filename, "r")) == NULL) {
 190         perror(filename);
 191         usage();
 192     }
 193
 194     while(fgets(symbol, sizeof(symbol), keepf)) {
 195         len = strlen(symbol);
 196         if(len && symbol[len-1] == '\n')
 197             symbol[len-1] = '\0';
 198
 199         add_to_keep_list(symbol);
 200     }
 201     fclose(keepf);
 202 }
 203
 204 /* ---------------------------- */
 205
 206 struct {
 207         const char *name;
 208         int     (*check)(int, const char *);    /* 1 if match, zero if not */
 209         int     (*hide)(int, const char *);     /* non-zero if error */
 210 } exec_formats[] = {
 211 #ifdef NLIST_AOUT
 212         {       "a.out",        check_aout,     hide_aout,      },
 213 #endif
 214 #ifdef NLIST_ECOFF
 215         {       "ECOFF",        check_elf64,    hide_elf64,     },
 216 #endif
 217 #ifdef NLIST_ELF32
 218         {       "ELF32",        check_elf32,    hide_elf32,     },
 219 #endif
 220 #ifdef NLIST_ELF64
 221         {       "ELF64",        check_elf64,    hide_elf64,     },
 222 #endif
 223 };
 224
 225 int hide_syms(const char *filename)
 226 {
 227         int fd, i, n, rv;
 228
 229         fd = open(filename, O_RDWR, 0);
 230         if (fd == -1) {
 231                 perror(filename);
 232                 return 1;
 233         }
 234
 235         rv = 0;
 236
 237         n = sizeof exec_formats / sizeof exec_formats[0];
 238         for (i = 0; i < n; i++) {
 239                 if (lseek(fd, 0, SEEK_SET) != 0) {
 240                         perror(filename);
 241                         goto err;
 242                 }
 243                 if ((*exec_formats[i].check)(fd, filename) != 0)
 244                         break;
 245         }
 246         if (i == n) {
 247                 fprintf(stderr, "%s: unknown executable format\n", filename);
 248                 goto err;
 249         }
 250
 251         if (verbose)
 252                 fprintf(stderr, "%s is an %s binary\n", filename,
 253                     exec_formats[i].name);
 254
 255         if (lseek(fd, 0, SEEK_SET) != 0) {
 256                 perror(filename);
 257                 goto err;
 258         }
 259         rv = (*exec_formats[i].hide)(fd, filename);
 260
 261 out:
 262         close (fd);
 263         return (rv);
 264
 265 err:
 266         rv = 1;
 267         goto out;
 268 }