xref: /openbsd-src/usr.sbin/crunchgen/crunchide.c (revision 9f79a69831e4879318a9c62b1da26ebbbfc9edc0)

/* $OpenBSD: crunchide.c,v 1.12 2017/10/29 08:45:53 mpi Exp $	 */

/*
 * Copyright (c) 1994 University of Maryland
 * All Rights Reserved.
 *
 * Permission to use, copy, modify, distribute, and sell this software and its
 * documentation for any purpose is hereby granted without fee, provided that
 * the above copyright notice appear in all copies and that both that
 * copyright notice and this permission notice appear in supporting
 * documentation, and that the name of U.M. not be used in advertising or
 * publicity pertaining to distribution of the software without specific,
 * written prior permission.  U.M. makes no representations about the
 * suitability of this software for any purpose.  It is provided "as is"
 * without express or implied warranty.
 *
 * U.M. DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL U.M.
 * BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * Author: James da Silva, Systems Design and Analysis Group
 *			   Computer Science Department
 *			   University of Maryland at College Park
 */
/*
 * crunchide.c - tiptoes through an a.out symbol table, hiding all defined
 *	global symbols.  Allows the user to supply a "keep list" of symbols
 *	that are not to be hidden.  This program relies on the use of the
 * 	linker's -dc flag to actually put global bss data into the file's
 * 	bss segment (rather than leaving it as undefined "common" data).
 *
 * 	The point of all this is to allow multiple programs to be linked
 *	together without getting multiple-defined errors.
 *
 *	For example, consider a program "foo.c".  It can be linked with a
 *	small stub routine, called "foostub.c", eg:
 *	    int foo_main(int argc, char **argv){ return main(argc, argv); }
 *      like so:
 *	    cc -c foo.c foostub.c
 *	    ld -dc -r foo.o foostub.o -o foo.combined.o
 *	    crunchide -k _foo_main foo.combined.o
 *	at this point, foo.combined.o can be linked with another program
 * 	and invoked with "foo_main(argc, argv)".  foo's main() and any
 * 	other globals are hidden and will not conflict with other symbols.
 *
 * TODO:
 *      - arrange that all the BSS segments start at the same address, so
 *	  that the final crunched binary BSS size is the max of all the
 *	  component programs' BSS sizes, rather than their sum.
 */

#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>

#include <elf.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "mangle.h"

void	usage(void);

void	add_to_keep_list(char *);
void	add_file_to_keep_list(char *);

void	hide_syms(char *);
void	elf_hide(int, char *);
int	in_keep_list(char *symbol);
int	crunchide_main(int argc, char *argv[]);

extern char	*__progname;
extern int elf_mangle;

int
crunchide_main(int argc, char *argv[])
{
	int             ch;

	while ((ch = getopt(argc, argv, "Mhk:f:")) != -1)
		switch (ch) {
		case 'M':
			elf_mangle = 1;
			break;
		case 'h':
			break;
		case 'k':
			add_to_keep_list(optarg);
			break;
		case 'f':
			add_file_to_keep_list(optarg);
			break;
		default:
			usage();
		}

	argc -= optind;
	argv += optind;

	if (argc == 0)
		usage();

	if (elf_mangle)
		init_mangle_state();

	while (argc) {
		hide_syms(*argv);
		argc--;
		argv++;
	}
	if (elf_mangle)
		fini_mangle_state();

	return 0;
}

struct keep {
	struct keep    *next;
	char           *sym;
} *keep_list;

void
add_to_keep_list(char *symbol)
{
	struct keep    *newp, *prevp, *curp;
	int             cmp = 0;

	for (curp = keep_list, prevp = NULL; curp; prevp = curp, curp = curp->next)
		if ((cmp = strcmp(symbol, curp->sym)) <= 0)
			break;

	if (curp && cmp == 0)
		return;		/* already in table */

	newp = calloc(1, sizeof(struct keep));
	if (newp)
		newp->sym = strdup(symbol);
	if (newp == NULL || newp->sym == NULL) {
		fprintf(stderr, "%s: out of memory for keep list\n", __progname);
		exit(1);
	}
	newp->next = curp;
	if (prevp)
		prevp->next = newp;
	else
		keep_list = newp;
}

int
in_keep_list(char *symbol)
{
	struct keep    *curp;
	int             cmp = 0;

	for (curp = keep_list; curp; curp = curp->next)
		if ((cmp = strcmp(symbol, curp->sym)) <= 0)
			break;

	return curp && cmp == 0;
}

void
add_file_to_keep_list(char *filename)
{
	FILE           *keepf;
	char            symbol[1024];
	int             len;

	if ((keepf = fopen(filename, "r")) == NULL) {
		perror(filename);
		usage();
	}
	while (fgets(symbol, sizeof(symbol), keepf)) {
		len = strlen(symbol);
		if (len && symbol[len - 1] == '\n')
			symbol[len - 1] = '\0';

		add_to_keep_list(symbol);
	}
	fclose(keepf);
}

void
hide_syms(char *filename)
{
	int             inf;
	struct stat     infstat;
	char           *buf;

	/*
         * Open the file and do some error checking.
         */

	if ((inf = open(filename, O_RDWR)) == -1) {
		perror(filename);
		return;
	}
	if (fstat(inf, &infstat) == -1) {
		perror(filename);
		close(inf);
		return;
	}
	if (infstat.st_size < sizeof(Elf_Ehdr) || infstat.st_size > SIZE_MAX) {
		fprintf(stderr, "%s: invalid file size\n", filename);
		close(inf);
		return;
	}
	if ((buf = mmap(NULL, infstat.st_size, PROT_READ | PROT_WRITE,
	    MAP_FILE | MAP_SHARED, inf, 0)) == MAP_FAILED) {
		fprintf(stderr, "%s: cannot map\n", filename);
		close(inf);
		return;
	}

	if (buf[0] == ELFMAG0 && buf[1] == ELFMAG1 &&
	    buf[2] == ELFMAG2 && buf[3] == ELFMAG3) {
		elf_hide(inf, buf);
		return;
	}

	close(inf);
}