/* $NetBSD: crunchide.c,v 1.14 2011/08/30 23:15:14 joerg Exp $ */

/*
 * Copyright (c) 1997 Christopher G. Demetriou.  All rights reserved.
 * 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 a 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:
 *      - resolve the theoretical hanging reloc problem (see check_reloc()
 *        below). I have yet to see this problem actually occur in any real
 *        program. In what cases will gcc/gas generate code that needs a
 *        relative reloc from a global symbol, other than PIC?  The
 *        solution is to not hide the symbol from the linker in this case,
 *        but to generate some random name for it so that it doesn't link
 *        with anything but holds the place for the reloc.
 *      - 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/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: crunchide.c,v 1.14 2011/08/30 23:15:14 joerg Exp $");
#endif

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>

#include "extern.h"

__dead static void usage(void);

static void add_to_keep_list(char *symbol);
static void add_file_to_keep_list(char *filename);

static int hide_syms(const char *filename);

static int verbose;

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

        setprogname(argv[0]);

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

        argc -= optind;
        argv += optind;

        if (argc == 0)
                usage();

        errors = 0;
        while (argc) {
                if (hide_syms(*argv))
                        errors = 1;
                argc--, argv++;
        }

        return errors;
}

static void
usage(void)
{
        fprintf(stderr,
                "Usage: %s [-k keep-symbol] [-f keep-list-file] object-file\n"
                "\t\t [object-file ...]\n",
                getprogname());
        exit(1);
}

/* ---------------------------- */

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

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

        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 = (struct keep *) malloc(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", getprogname());
                exit(1);
        }

        newp->next = curp;
        if (prevp)
                prevp->next = newp;
        else
                keep_list = newp;
}

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

        cmp = 0;

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

        return curp && cmp == 0;
}

static 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, 1024, keepf)) {
                len = strlen(symbol);
                if (len && symbol[len-1] == '\n')
                        symbol[len-1] = '\0';

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

/* ---------------------------- */

static struct {
        const char *name;
        int     (*check)(int, const char *);    /* 1 if match, zero if not */
        int     (*hide)(int, const char *);     /* non-zero if error */
} exec_formats[] = {
#ifdef NLIST_AOUT
        {       "a.out",        check_aout,     hide_aout,      },
#endif
#ifdef NLIST_COFF
        {       "COFF",         check_coff,     hide_coff,      },
#endif
#ifdef NLIST_ECOFF
        {       "ECOFF",        check_ecoff,    hide_ecoff,     },
#endif
#ifdef NLIST_ELF32
        {       "ELF32",        check_elf32,    hide_elf32,     },
#endif
#ifdef NLIST_ELF64
        {       "ELF64",        check_elf64,    hide_elf64,     },
#endif
};

static int
hide_syms(const char *filename)
{
        int fd, i, n, rv;

        fd = open(filename, O_RDWR, 0);
        if (fd == -1) {
                perror(filename);
                return 1;
        }

        rv = 0;

        n = sizeof exec_formats / sizeof exec_formats[0];
        for (i = 0; i < n; i++) {
                if (lseek(fd, 0, SEEK_SET) != 0) {
                        perror(filename);
                        goto err;
                }
                if ((*exec_formats[i].check)(fd, filename) != 0)
                        break;
        }
        if (i == n) {
                fprintf(stderr, "%s: unknown executable format\n", filename);
                goto err;
        }

        if (verbose)
                fprintf(stderr, "%s is an %s binary\n", filename,
                    exec_formats[i].name);

        if (lseek(fd, 0, SEEK_SET) != 0) {
                perror(filename);
                goto err;
        }
        rv = (*exec_formats[i].hide)(fd, filename);

out:
        close(fd);
        return rv;

err:
        rv = 1;
        goto out;
}