OpenBSD-4.6/usr.sbin/crunchgen/crunchide.c
/* $OpenBSD: crunchide.c,v 1.2 2008/08/22 15:38:37 deraadt 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:
* - 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 <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <a.out.h>
#include <sys/types.h>
#ifdef _NLIST_DO_ECOFF
#include <sys/exec_ecoff.h>
#endif
#include <sys/mman.h>
#include <sys/stat.h>
/*
* if __ELF__ is defined, do not bother supporting AOUT.
*/
#if defined(_NLIST_DO_AOUT) && !(defined(__ELF__))
#define DO_AOUT
#endif
void usage(void);
void add_to_keep_list(char *);
void add_file_to_keep_list(char *);
void hide_syms(char *);
#ifdef _NLIST_DO_ECOFF
void ecoff_hide(int, char *);
#endif
#ifdef _NLIST_DO_ELF
void elf_hide(int, char *);
#endif
extern char *__progname;
int
crunchide_main(int argc, char *argv[])
{
int ch;
while ((ch = getopt(argc, argv, "hk:f:")) != -1)
switch (ch) {
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();
while (argc) {
hide_syms(*argv);
argc--;
argv++;
}
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;
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 *) 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);
}
int nsyms, ntextrel, ndatarel;
struct exec *hdrp;
char *aoutdata, *strbase;
struct relocation_info *textrel, *datarel;
struct nlist *symbase;
#define SYMSTR(sp) &strbase[(sp)->n_un.n_strx]
/* is the symbol a global symbol defined in the current file? */
#define IS_GLOBAL_DEFINED(sp) \
(((sp)->n_type & N_EXT) && ((sp)->n_type & N_TYPE) != N_UNDF)
#ifdef DO_AOUT
#if defined(__sparc__)
/* is the relocation entry dependent on a symbol? */
#define IS_SYMBOL_RELOC(rp) \
((rp)->r_extern || \
((rp)->r_type >= RELOC_BASE10 && (rp)->r_type <= RELOC_BASE22) || \
(rp)->r_type == RELOC_JMP_TBL)
#else
/* is the relocation entry dependent on a symbol? */
#define IS_SYMBOL_RELOC(rp) \
((rp)->r_extern||(rp)->r_baserel||(rp)->r_jmptable)
#endif
#endif
void check_reloc(char *filename, struct relocation_info * relp);
void
hide_syms(char *filename)
{
int inf;
struct stat infstat;
#ifdef DO_AOUT
struct relocation_info *relp;
struct nlist *symp;
u_char zero = 0;
#endif
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(struct exec)) {
fprintf(stderr, "%s: short file\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;
}
#ifdef _NLIST_DO_ELF
if (buf[0] == 0x7f && (buf[1] == 'E' || buf[1] == 'O') &&
buf[2] == 'L' && buf[3] == 'F') {
elf_hide(inf, buf);
return;
}
#endif /* _NLIST_DO_ELF */
#ifdef _NLIST_DO_ECOFF
if (!ECOFF_BADMAG((struct ecoff_exechdr *) buf)) {
ecoff_hide(inf, buf);
return;
}
#endif /* _NLIST_DO_ECOFF */
#ifdef DO_AOUT
aoutdata = buf;
/*
* Check the header and calculate offsets and sizes from it.
*/
hdrp = (struct exec *) aoutdata;
if (N_BADMAG(*hdrp)) {
fprintf(stderr, "%s: bad magic: not an a.out, ecoff or elf file\n",
filename);
close(inf);
return;
}
textrel = (struct relocation_info *) (aoutdata + N_TRELOFF(*hdrp));
datarel = (struct relocation_info *) (aoutdata + N_DRELOFF(*hdrp));
symbase = (struct nlist *) (aoutdata + N_SYMOFF(*hdrp));
strbase = (char *) (aoutdata + N_STROFF(*hdrp));
ntextrel = hdrp->a_trsize / sizeof(struct relocation_info);
ndatarel = hdrp->a_drsize / sizeof(struct relocation_info);
nsyms = hdrp->a_syms / sizeof(struct nlist);
/*
* Zap the type field of all globally-defined symbols. The linker will
* subsequently ignore these entries. Don't zap any symbols in the
* keep list.
*/
for (symp = symbase; symp < symbase + nsyms; symp++)
if (IS_GLOBAL_DEFINED(symp) && !in_keep_list(SYMSTR(symp))) {
/*
* XXX Our VM system has some problems, so
* avoid the VM system....
*/
lseek(inf, (off_t) ((void *) &symp->n_type -
(void *) buf), SEEK_SET);
write(inf, &zero, sizeof zero);
symp->n_type = 0;
}
/*
* Check whether the relocation entries reference any symbols that we
* just zapped. I don't know whether ld can handle this case, but I
* haven't encountered it yet. These checks are here so that the program
* doesn't fail silently should such symbols be encountered.
*/
for (relp = textrel; relp < textrel + ntextrel; relp++)
check_reloc(filename, relp);
for (relp = datarel; relp < datarel + ndatarel; relp++)
check_reloc(filename, relp);
msync(buf, infstat.st_size, MS_SYNC);
munmap(buf, infstat.st_size);
close(inf);
#endif /* DO_AOUT */
}
#ifdef DO_AOUT
void
check_reloc(char *filename, struct relocation_info * relp)
{
/* bail out if we zapped a symbol that is needed */
if (IS_SYMBOL_RELOC(relp) && symbase[relp->r_symbolnum].n_type == 0) {
fprintf(stderr,
"%s: oops, have hanging relocation for %s: bailing out!\n",
filename, SYMSTR(&symbase[relp->r_symbolnum]));
exit(1);
}
}
#endif /* DO_AOUT */