Message-ID: <20090624133148.GA12878@streefland.net>
Date:	Wed, 24 Jun 2009 15:31:48 +0200
From:	Dick Streefland <dick@...eefland.net>
To:	Amerigo Wang <xiyou.wangcong@...il.com>
Cc:	linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kconfig: simplification of scripts/extract-ikconfig

On Wednesday 2009-06-24 13:46, Dick Streefland wrote:
| Because I don't want to rely on a particular version of grep, I've
| modified the script to use perl instead. I hope that's OK. Below is
| a new patch.
<snip>

I found a way to work around the differences in behavior of grep.
Older versions of grep report the byte offset of the start of the
line instead of the byte offset of the pattern. By using tr to
make sure the pattern is always at the start of a "line", both old
and new versions of grep can be used.

Below is a third version of the patch without a dependency on perl,
which may be undesirable in some situations.

======================================================================

I've rewritten the extract-ikconfig script to extract the kernel
configuration from a kernel compiled with CONFIG_IKCONFIG. The main
motivation for the rewrite was to remove the dependency on the
external C program binoffset.c, which is compiled on the initial run.

The binoffset executable is invoked with a relative path, which means
that the old script can only be run from the top of the kernel tree,
and only when you have write permission in the scripts directory.
The new script uses tr/grep/tail/zcat only, and can be invoked from
anywhere. The binoffset.c program has been removed.

Signed-off-by: Dick Streefland <dick@...eefland.net>
---

 Documentation/dontdiff   |    1 -
 scripts/.gitignore       |    1 -
 scripts/binoffset.c      |  163 ----------------------------------------------
 scripts/extract-ikconfig |  113 ++++++++++++-------------------
 4 files changed, 44 insertions(+), 234 deletions(-)

diff --git a/Documentation/dontdiff b/Documentation/dontdiff
index 88519da..6fef118 100644
--- a/Documentation/dontdiff
+++ b/Documentation/dontdiff
@@ -68,7 +68,6 @@ autoconf.h*
 bbootsect
 bin2c
 binkernel.spec
-binoffset
 bootsect
 bounds.h
 bsetup
diff --git a/scripts/.gitignore b/scripts/.gitignore
index b939fbd..a1f52cb 100644
--- a/scripts/.gitignore
+++ b/scripts/.gitignore
@@ -6,4 +6,3 @@ kallsyms
 pnmtologo
 bin2c
 unifdef
-binoffset
diff --git a/scripts/binoffset.c b/scripts/binoffset.c
deleted file mode 100644
index 1a2e39b..0000000
--- a/scripts/binoffset.c
+++ /dev/null
@@ -1,163 +0,0 @@
-/***************************************************************************
- * binoffset.c
- * (C) 2002 Randy Dunlap <rdunlap@...otime.net>
-
-#   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;
-unsigned 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);
-}
-
-void 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;
-}
-
-void 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: %ld\n", err < 0 ? (long)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 ("%ld\n", firstloc);
-	fprintf (stderr, "%ld\n", firstloc);
-
-	exit (num_matches ? 0 : 2);
-}
-
-/* end binoffset.c */
diff --git a/scripts/extract-ikconfig b/scripts/extract-ikconfig
index 72997c3..37f30d3 100755
--- a/scripts/extract-ikconfig
+++ b/scripts/extract-ikconfig
@@ -1,78 +1,53 @@
 #!/bin/sh
-# extracts .config info from a [b]zImage file
-# uses: binoffset (new), dd, zcat, strings, grep
-# $arg1 is [b]zImage filename
-
-binoffset="./scripts/binoffset"
-test -e $binoffset || cc -o $binoffset ./scripts/binoffset.c || exit 1
-
-IKCFG_ST="0x49 0x4b 0x43 0x46 0x47 0x5f 0x53 0x54"
-IKCFG_ED="0x49 0x4b 0x43 0x46 0x47 0x5f 0x45 0x44"
-dump_config() {
-    file="$1"
-
-    start=`$binoffset $file $IKCFG_ST 2>/dev/null`
-    [ "$?" != "0" ] && start="-1"
-    if [ "$start" -eq "-1" ]; then
-	return
-    fi
-    end=`$binoffset $file $IKCFG_ED 2>/dev/null`
-
-    start=`expr $start + 8`
-    size=`expr $end - $start`
-
-    dd if="$file" ibs=1 skip="$start" count="$size" 2>/dev/null | zcat
-
-    clean_up
-    exit 0
-}
-
-
-usage()
+# ----------------------------------------------------------------------
+# extract-ikconfig - Extract the .config file from a kernel image
+#
+# This will only work when the kernel was compiled with CONFIG_IKCONFIG.
+#
+# The obscure use of the "tr" filter is to work around older versions of
+# "grep" that report the byte offset of the line instead of the pattern.
+#
+# (c) 2009, Dick Streefland <dick@...eefland.net>
+# Licensed under the terms of the GNU General Public License.
+# ----------------------------------------------------------------------
+
+gz1='\037\213\010'
+gz2='01'
+cf1='IKCFG_ST\037\213\010'
+cf2='0123456789'
+
+dump_config()
 {
-	echo "  usage: extract-ikconfig [b]zImage_filename"
-}
-
-clean_up()
-{
-	if [ "$TMPFILE" != "" ]; then
-		rm -f $TMPFILE
+	if	pos=`tr "$cf1\n$cf2" "\n$cf2=" < "$1" | grep -abo "^$cf2"`
+	then
+		pos=${pos%%:*}
+		tail -c+$(($pos+8)) "$1" | zcat -q
+		exit 0
 	fi
 }
 
-if [ $# -lt 1 ]
+# Check invocation:
+me=${0##*/}
+img=$1
+if	[ $# -ne 1 -o ! -s "$img" ]
 then
-	usage
-	exit 1
+	echo "Usage: $me <kernel-image>" >&2
+	exit 2
 fi
 
-TMPFILE=`mktemp -t ikconfig-XXXXXX` || exit 1
-image="$1"
-
-# vmlinux: Attempt to dump the configuration from the file directly
-dump_config "$image"
-
-GZHDR1="0x1f 0x8b 0x08 0x00"
-GZHDR2="0x1f 0x8b 0x08 0x08"
-
-# vmlinux.gz: Check for a compressed images
-off=`$binoffset "$image" $GZHDR1 2>/dev/null`
-[ "$?" != "0" ] && off="-1"
-if [ "$off" -eq "-1" ]; then
-	off=`$binoffset "$image" $GZHDR2 2>/dev/null`
-	[ "$?" != "0" ] && off="-1"
-fi
-if [ "$off" -eq "0" ]; then
-	zcat <"$image" >"$TMPFILE"
-	dump_config "$TMPFILE"
-elif [ "$off" -ne "-1" ]; then
-	(dd ibs="$off" skip=1 count=0 && dd bs=512k) <"$image" 2>/dev/null | \
-		zcat >"$TMPFILE"
-	dump_config "$TMPFILE"
-fi
-
-echo "ERROR: Unable to extract kernel configuration information."
-echo "       This kernel image may not have the config info."
-
-clean_up
+# Initial attempt for uncompressed images or objects:
+dump_config "$img"
+
+# That didn't work, so decompress and try again:
+tmp=/tmp/ikconfig$$
+trap "rm -f $tmp" 0
+for	pos in `tr "$gz1\n$gz2" "\n$gz2=" < "$img" | grep -abo "^$gz2"`
+do
+	pos=${pos%%:*}
+	tail -c+$pos "$img" | zcat 2> /dev/null > $tmp
+	dump_config $tmp
+done
+
+# Bail out:
+echo "$me: Cannot find kernel config." >&2
 exit 1
--
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