utility: add a simple tool for dumping the kernel config

utility: add a simple tool for dumping the kernel config

Adds dump_kernel_config.c which takes in a file, reads it
all in to memory, then walks the blob until it can determine
the location of the kernel command line.

This is needed to allow the kernel config to inform legacy bootloader
configuration during autoupdates without packaging up dm-verity specific
options in some additional update metadata.

TEST=manual run over build_kernel_image.sh output
BUG=chromium-os:327

[Bill Richardson, 2010-06-24 18:33:40]

A couple of comments.

You'll also have to make changes to the ebuild to ensure that this utility is
built for the target. At the moment, only the cgpt tool is.

http://codereview.chromium.org/2811029/diff/1/3
File utility/dump_kernel_config.c (right):

http://codereview.chromium.org/2811029/diff/1/3#newcode16
utility/dump_kernel_config.c:16: #include "host_common.h"
You don't need "host_common.h" here. You should use "vboot_struct.h" instead.

http://codereview.chromium.org/2811029/diff/1/3#newcode93
utility/dump_kernel_config.c:93: blob = ReadFile(infile, &blob_size);
Reading in the entire 3M kernel into ram probably isn't a great idea on the
target machine. You might consider using mmap() instead.

[Will Drewry, 2010-06-25 03:15:28]

http://codereview.chromium.org/2811029/diff/1/3
File utility/dump_kernel_config.c (right):

http://codereview.chromium.org/2811029/diff/1/3#newcode16
utility/dump_kernel_config.c:16: #include "host_common.h"
On 2010/06/24 18:33:40, Bill Richardson wrote:
> You don't need "host_common.h" here. You should use "vboot_struct.h" instead.

Done.  Added utility.h for error() as well

http://codereview.chromium.org/2811029/diff/1/3#newcode93
utility/dump_kernel_config.c:93: blob = ReadFile(infile, &blob_size);
On 2010/06/24 18:33:40, Bill Richardson wrote:
> Reading in the entire 3M kernel into ram probably isn't a great idea on the
> target machine. You might consider using mmap() instead.

Done.

Added a local MapFile() helper based on the ReadFile code.  I didn't push it to
the host_misc.c utilities since I didn't abstract mmap() and this isn't meant
for firmware-time use, but I'm happy to move it over there if it makes more
sense.

[Bill Richardson, 2010-06-25 14:04:42]

LGTM