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authorJulius Werner <jwerner@chromium.org>2019-12-11 16:19:48 -0800
committerPhilipp Deppenwiese <zaolin.daisuki@gmail.com>2020-10-30 11:13:35 +0000
commit0655f78041ef617844f436306fa5431e211f4431 (patch)
tree90e3382ce42dbdb6636b52f028f34403a0c4f56b /Documentation/arch
parent0a9eea0f5bb192a7e92115c87480836fb3395471 (diff)
commonlib/bsd: Add new CBFS core implementation
This patch adds a new CBFS implementation that is intended to replace the existing commonlib/cbfs.c. The new implementation is designed to meet a bunch of current and future goals that in aggregate make it easier to start from scratch than to adapt the exisiting implementation: 1. Be BSD-licensed so it can evetually be shared with libpayload. 2. Allow generating/verifying a metadata hash for future CBFS per-file verification (see [1][2]). 3. Be very careful about reading (not mmaping) all data only once, to be suitable for eventual TOCTOU-safe verification. 4. Make it possible to efficiently implement all current and future firmware use cases (both with and without verification). The main primitive is the cbfs_walk() function which will traverse a CBFS and call a callback for every file. cbfs_lookup() uses this to implement the most common use case of finding a file so that it can be read. A host application using this code (e.g. coreboot, libpayload, cbfstool) will need to provide a <cbfs_glue.h> header to provide the glue to access the respective CBFS storage backend implementation. This patch merely adds the code, the next patch will integrate it into coreboot. [1]: https://www.youtube.com/watch?v=Hs_EhewBgtM [2]: https://osfc.io/uploads/talk/paper/47/The_future_of_firmware_verification_in_coreboot.pdf (Note: In early discussions the metadata hash was called "master hash".) Change-Id: Ica64c1751fa37686814c0247460c399261d5814c Signed-off-by: Julius Werner <jwerner@chromium.org> Reviewed-on: https://review.coreboot.org/c/coreboot/+/38421 Reviewed-by: Aaron Durbin <adurbin@chromium.org> Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
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