util: Add tools for dumping and inserting KBC1126 firmware images.

Change-Id: Ic521b177b9602ff042312cccaaa89371db7c5855
Signed-off-by: Iru Cai <mytbk920423@gmail.com>
Reviewed-on: https://review.coreboot.org/19071
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

util/kbc1126/README.md

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+KBC1126 firmware tools
+======================
+
+Many HP laptops use 8051-based SMSC KBC1098/KBC1126 as embedded
+controller. Two blobs can be found in the HP firmware images. The
+`kbc1126_ec_dump` and `kbc1126_ec_insert` tools are used to dump the
+two blobs from the factory firmware and insert them to the firmware
+image.
+
+
+Firmware format
+---------------
+
+We can easily find the BIOS region of the HP laptop firmware from the
+HP firmware update tool, which can be downloaded from the HP
+website. Now I take HP Elitebook 8470p as an example. This laptop has
+a 16MB flash chip, the last 5MB of which is the BIOS region.
+
+I use [radare2](https://radare.org) to analyze the firmware. Open the
+firmware image, and we can see 8 bytes at `$s-0x100` (`$s` means the
+image size).
+
+  [0x00000000]> x @ $s-0x100  
+  - offset -   0 1  2 3  4 5  6 7  8 9  A B  C D  E F  0123456789ABCDEF  
+  0x00ffff00  fff7 0008 f700 08ff 0000 0000 0000 0000  ................  
+
+X86 machines map the firmware at the end of the memory address
+space. These 8 bytes tell the address of the two blobs, which we call
+FW1 (uses bytes 0-3) and FW2 (uses bytes 4-7).
+
+Let's look at FW1. The first two bytes mean the address of FW1 is
+0xfff700 (these two bytes use big endian), i.e. `$s-0x900`. Byte 2 and
+3 are just complements of byte 1 and 2 (in this case,
+0x0008=0xffff-0xfff7).
+
+  [0x00000000]> x @ $s-0x900  
+  - offset -   0 1  2 3  4 5  6 7  8 9  A B  C D  E F  0123456789ABCDEF  
+  0x00fff700  fc07 c13e 02ff 1000 0000 0000 0000 0000  ...>............  
+
+Both FW1 and FW2 use the same format: the first two bytes is payload
+length, then a two-byte checksum, then the payload. The payload length
+and checksum are both in little endian. The checksum is
+[SYSV checksum](https://en.wikipedia.org/wiki/SYSV_checksum).
+
+
+How to use the tools
+--------------------
+
+`kbc1126_ec_dump` is used to dump FW1 and FW2. Run `kbc1126_ec_dump
+bios.rom`, then bios.rom.fw1 and bios.rom.fw2 are generated in the
+working directory.
+
+`kbc1126_ec_insert` will overwrite a firmware image by inserting FW1
+and FW2 in it. Please run it for its usage. You need to specify the
+offsets for FW1 and FW2. Using negative offset is recommended, which
+means the distance to the end of the image. For example, if we want to
+insert FW1 and FW2 at `$s-0x900` and `$s-0x90000` as the hp/8470p
+factory firmware to coreboot.rom, you can run `kbc1126_ec_insert
+coreboot.rom bios.rom.fw1 bios.rom.fw2 -0x900 -0x90000`.