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SubjectRe: How to check the kernel compile options ?
On Wed, 13 Feb 2002, Bill Davidsen wrote:

| On Wed, 13 Feb 2002, Ben Greear wrote:
|
[snippage]
|
| No, but there's no reason to have it part of the kernel image as the only
| solution. It works as a module, it works as a flat text data file in the
| modules directory (except for those who can't match kernel to modules),
| and ther's no reason why this can't exist somewhere which has no impact on
| the size of the kernel image.

I agree, if I understand you correctly.

I don't see a need for a CONFIG_SAVE_CONFIG option with value 'm'.
kbuild in 2.5 (or any script like 'installkernel') can do that by
copying the current .config file to the modules install directory
or the /boot directory.

I was hoping that (e)grep could search a (b)zImage file for
a binary pattern like the gzip header, but I couldn't make it
work. I ended up writing a binary pattern search tool that
returns the offset of the located pattern, and then I feed
that value to tail | gunzip > strings | grep to get the
CONFIG text that was saved by the code that I posted yesterday.
I still plan to make this a config/build option (y/n) and
remove the leading "CONFIG_" parts of the strings.

binoffset.c and extract-config (script) attached.

--
~Randy

#! /bin/bash
# extracts .config info from a [b]zImage file
# uses binoffset (new), tail, gunzip, strings, and grep
# $arg1 is [b]zImage filename

gziphdr=`binoffset $1 0x1f 0x8b 0x08 0x0`
# increment by 1 since tail offsets are 1-based, not 0-based
gziphdr=$((gziphdr + 1))

tail -c +$gziphdr $1 | gunzip > $1.tmp
strings $1.tmp | grep CONFIG_ > $1.old.config
rm $1.tmp/***************************************************************************
* binoffset.c
* (C) 2002 Randy Dunlap <rddunlap@osdl.org>
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

# binoffset.c:
# - searches a (binary) file for a specified (binary) pattern
# - returns the offset of the located pattern or ~0 if not found
# - exits with exit status 0 normally or non-0 if pattern is not found
# or any other error occurs.

****************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#define VERSION "0.1"
#define BUF_SIZE (16 * 1024)
#define PAT_SIZE 100
char *progname;
char *inputname;
int inputfd;
int bix; /* buf index */
unsigned char patterns [PAT_SIZE] = {0}; /* byte-sized pattern array */
int pat_len; /* actual number of pattern bytes */
unsigned char *madr; /* mmap address */
size_t filesize;
int num_matches = 0;
off_t firstloc = 0;
void usage (void)
{
fprintf (stderr, "%s ver. %s\n", progname, VERSION);
fprintf (stderr, "usage: %s filename pattern_bytes\n",
progname);
fprintf (stderr, " [prints location of pattern_bytes in file]\n");
exit (1);
}
int get_pattern (int pat_count, char *pats [])
{
int ix, err, tmp;
#ifdef DEBUG
fprintf (stderr,"get_pattern: count = %d\n", pat_count);
for (ix = 0; ix < pat_count; ix++)
fprintf (stderr, " pat # %d: [%s]\n", ix, pats[ix]);
#endif
for (ix = 0; ix < pat_count; ix++) {
tmp = 0;
err = sscanf (pats[ix], "%5i", &tmp);
if (err != 1 || tmp > 0xff) {
fprintf (stderr, "pattern or value error in pattern # %d [%s]\n",
ix, pats[ix]);
usage ();
}
patterns [ix] = tmp;
}
pat_len = pat_count;
}
int search_pattern (void)
{
for (bix = 0; bix < filesize; bix++) {
if (madr[bix] == patterns[0]) {
if (memcmp (&madr[bix], patterns, pat_len) == 0) {
if (num_matches == 0)
firstloc = bix;
num_matches++;
}
}
}
}
#ifdef NOTDEF
size_t get_filesize (int fd)
{
off_t end_off = lseek (fd, 0, SEEK_END);
lseek (fd, 0, SEEK_SET);
return (size_t) end_off;
}
#endif
size_t get_filesize (int fd)
{
int err;
struct stat stat;
err = fstat (fd, &stat);
fprintf (stderr, "filesize: %d\n", err < 0 ? err : stat.st_size);
if (err < 0)
return err;
return (size_t) stat.st_size;
}
int main (int argc, char *argv [])
{
progname = argv[0];
if (argc < 3)
usage ();
get_pattern (argc - 2, argv + 2);
inputname = argv[1];
inputfd = open (inputname, O_RDONLY);
if (inputfd == -1) {
fprintf (stderr, "%s: cannot open '%s'\n",
progname, inputname);
exit (3);
}
filesize = get_filesize (inputfd);
madr = mmap (0, filesize, PROT_READ, MAP_PRIVATE, inputfd, 0);
if (madr == MAP_FAILED) {
fprintf (stderr, "mmap error = %d\n", errno);
close (inputfd);
exit (4);
}
search_pattern ();
if (munmap (madr, filesize))
fprintf (stderr, "munmap error = %d\n", errno);
if (close (inputfd))
fprintf (stderr, "%s: error %d closing '%s'\n",
progname, errno, inputname);
fprintf (stderr, "number of pattern matches = %d\n", num_matches);
if (num_matches == 0)
firstloc = ~0;
printf ("%d\n", firstloc);
fprintf (stderr, "%d\n", firstloc);
exit (num_matches ? 0 : 2);
}
/* end binoffset.c */
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