kconfig: simplification of scripts/extract-ikconfig

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. This script
requires GNU grep 2.5 (released 2002-03-13) or higher, because the -o
option was introduced in that version.

Signed-off-by: Dick Streefland <dick@streefland.net>
LKML-Reference: <20091006203540.GA14634@streefland.net>
Tested-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 44 insertions, 83 deletions

diff --git a/scripts/extract-ikconfig b/scripts/extract-ikconfig
index de233ff43c1c..37f30d36c944 100755
--- a/scripts/extract-ikconfig
+++ b/scripts/extract-ikconfig
@@ -1,92 +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 $IKCFG_ED 2>/dev/null`
-    [ "$?" != "0" ] && end="-1"
-    if [ "$end" -eq "-1" ]; then
-        return
-    fi
-
-    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()
-{
-        echo "  usage: extract-ikconfig [b]zImage_filename"
-}
-
-clean_up()
+# ----------------------------------------------------------------------
+# 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@streefland.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()
 {
-        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"
-
-ELFHDR="0x7f 0x45 0x4c 0x46"
-
-# 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 "$TMPFILE"
-
-# check if this is simply an ELF file
-else
-        off=`$binoffset "$image" $ELFHDR 2>/dev/null`
-        [ "$?" != "0" ] && off="-1"
-        if [ "$off" -eq "0" ]; then
-                dump_config "$image"
-        fi
-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