cbfstool: allow user to explicitly specify header location

There potentially could be multiple CBFS instances present in the
firmware image. cbfstool should be able to operate on any of them, not
just the first one present.

To accomplish that, allow all CBFS commands to accept the -H parameter
(which specifies the exact CBFS header location in the image).

If this parameter is specified, the image is not searched for the CBFS
header, only the specified location is checked for validity, If the
location is valid, it is considered to be the CBFS header, if not -
the tool exits with an error status.

Note, that default behavior of the tool does not change.

BRANCH=storm
BUG=chrome-os-partner:34161, chromium:445938
TEST=run the following experiments:

  - examined an image with three CBFS instances, was able to print all
    of them.

  - built a rambi coreboot image and tried the following (cbfstool output abbreviated):

  $ ./util/cbfstool/cbfstool /build/rambi/firmware/coreboot.rom print
  coreboot.rom: 8192 kB, bootblocksize 2448, romsize 8388608, offset 0x700000
  alignment: 64 bytes, architecture: x86

  Name                           Offset     Type         Size
  cmos_layout.bin                0x700000   cmos_layout  1164
  ...
  (empty)                        0x7ec600   null         77848
  $ \od -tx4 -Ax /build/rambi/firmware/coreboot.rom | tail -2
  7ffff0 fff67de9 000000ff fff6dfe9 fffff650
  800000
  $ ./util/cbfstool/cbfstool /build/rambi/firmware/coreboot.rom print  -H 0x7ff650
  coreboot.rom: 8192 kB, bootblocksize 2448, romsize 8388608, offset 0x700000
  alignment: 64 bytes, architecture: x86

  Name                           Offset     Type         Size
  cmos_layout.bin                0x700000   cmos_layout  1164
  ...
  (empty)                        0x7ec600   null         77848
  $ ./util/cbfstool/cbfstool /build/rambi/firmware/coreboot.rom print  -H 0x7ff654
  E: /build/rambi/firmware/coreboot.rom does not have CBFS master header.
  E: Could not load ROM image '/build/rambi/firmware/coreboot.rom'.
  $

Change-Id: I486092e222c96c65868ae7d41a9e8976ffcc93c4
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/237485
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Reviewed-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-by: Stefan Reinauer <reinauer@google.com>
3 files changed