/* $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;
}