[kernel] r17223 - people/benh
Ben Hutchings
benh at alioth.debian.org
Fri Apr 15 01:53:16 UTC 2011
Author: benh
Date: Fri Apr 15 01:53:14 2011
New Revision: 17223
Log:
Add script for decompressing vmlinuz
Added:
people/benh/zcat-linux-image (contents, props changed)
Added: people/benh/zcat-linux-image
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ people/benh/zcat-linux-image Fri Apr 15 01:53:14 2011 (r17223)
@@ -0,0 +1,74 @@
+#!/usr/bin/python
+
+# Copyright 2010 Ben Hutchings
+#
+# 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+
+import os, struct, zlib
+
+def zcat_vmlinuz(f):
+ f.seek(0, 0)
+ head = f.read(65536)
+
+ try:
+ # Look for gzip-deflate header
+ off = head.index('\x1f\x8b\x08')
+ except ValueError:
+ pass
+ else:
+ return gzcat(f, head, off)
+
+ # Look for likely lzma header
+ off = head.index('\x00\x00\x00\x02\xff\xff\xff\xff\xff\xff\xff\xff') - 1
+ return lzcat(f, head, off)
+
+def gzcat(f, head, off):
+ # We can't use gzip.GzipFile because that complains if there is
+ # trailing data, which is the case for ELFBoot kernel images.
+ # Use zlib directly.
+ zo = zlib.decompressobj(-15)
+
+ flags = ord(head[off + 3])
+ off += 10 # fixed header
+ if flags & 0x04: # FEXTRA
+ off += 2 + struct.unpack('<H', head[off:off+2])[0]
+ if flags & 0x08: # FNAME
+ off = head.index('\0', off) + 1
+ if flags & 0x10: # FCOMMENT
+ off = head.index('\0', off) + 1
+ if flags & 0x02: # FHCRC
+ off += 2
+ assert not (flags & 0xe0) # reserved
+
+ # Decompress following deflate blocks
+ f.seek(off)
+ image = zo.decompress(f.read()) + zo.flush()
+
+ # Verify decompressed data against gzip trailer
+ assert (struct.unpack('<LL', zo.unused_data[:8]) ==
+ (zlib.crc32(image) & 0xffffffffL, len(image)))
+
+ sys.stdout.write(image)
+ sys.stdout.flush()
+
+def lzcat(f, head, off):
+ os.dup2(f.fileno(), 0)
+ f.close()
+ os.lseek(0, off, os.SEEK_SET)
+ os.execvp('lzcat', ['lzcat', '-t'])
+
+if __name__ == '__main__':
+ import sys
+ zcat_vmlinuz(open(sys.argv[1], 'rb'))
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