How was your last week?
Let’s say that it was a bit unexpected.
I spent the majority of it trying to wrap my head around the ELF (Executable Linkable Format) specification.
I used this new acquired knowledge to improve the utility cbfstool and allow it to extract payloads contained inside a CBFS directly into ELF instead of SELF (commit).
In order to achieve this cbfstool has to do a few things:
- Extract the payload from the coreboot image
- Parse the segment table contained inside the SELF payload in order to find out how many and which segments are present.
- Using the elf_writer API generate a compliant ELF header
- Take the content from each segment and copy it to the correspondent ELF section header and configure it accordingly
- Once the section table is filled out, use elf_writer to generate the program header table and write out the final ELF
The final results would allow to, for example, easily move payloads from a CBFS to another one without having to re-build the payload, coreboot rom or mess with the build system configuration.
Right now the implementation it’s not complete yet but it works quite well with a good chunk of the payloads commonly used with coreboot such as SeaBIOS, coreinfo, nvramcui and others.
The major hurdles right now are to get the GRUB payload to work and add a way to handle the extraction of a compressed payload.
Wait a minute! Weren’t you working on SerialICE?
You are quite the inquisitive type, aren’t you?
Yes, my main goal is still to continue integrating SerialICE and coreboot.
Unfortunately there have been a few showstoppers this week, first my only test clip broke and now my target, Lenovo x60, stopped working and I am no longer able to flash its BIOS chip.
I already ordered a replacement but it’ll probably take a bit more than a week to arrive.
In the meantime my mentor (adurbin) kindly pointed out the task above to keep me busy while waiting.
What are your plans for the next week?
I plan to finish implementing the functionality described above and test all the remaining payloads.
Hopefully I will also be able to start looking at some of the other tasks that have been suggested to me by my mentors.
That’s it for today, see you next week!