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      1 /* $NetBSD: crunchide.c,v 1.14 2011/08/30 23:15:14 joerg 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 1.14 2011/08/30 23:15:14 joerg 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 __dead static void usage(void);
     81 
     82 static void add_to_keep_list(char *symbol);
     83 static void add_file_to_keep_list(char *filename);
     84 
     85 static int hide_syms(const char *filename);
     86 
     87 static 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 static 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 static struct keep {
    140 	struct keep *next;
    141 	char *sym;
    142 } *keep_list;
    143 
    144 static 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 static 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 static 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 static 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 }
    280