How to decompress LZ4 compressed u-boot

SpookyHands · June 14, 2022 at 5:10 PM

I'm trying to modify the bootloader for my Amlogic device without having to recompile it.

Bl33/u-boot is LZ4 compressed with a nonstandard header so I'm not able to decompress it with any standard LZ4 programs. Does anyone know how or of any scripts to decompress u-boot?

**chewitt** · June 15, 2022 at 5:59 AM

The boot binaries are signed. What box/SoC is inside?

SpookyHands · June 16, 2022 at 5:25 AM

Yes the signing tool has an LZ4 compression option

Code

aml_encrypt_g12a --bl3sig --input u-boot.bin --compress lz4 --output u-boot.enc --level v3 --type bl33

But it uses a custom frame header that's not recognized by the standard LZ4 program. I was just wondering if there is an easy solution for decompression.

This isn't really specific to any box, I have seen the LZ4C magic in a number of bootloaders from different boxes indicating uboot is compressed.

**chewitt** · June 16, 2022 at 2:21 PM

See https://github.com/LibreELEC/amlogic-boot-fip/ .. there are some useful links in the README for the repo to other tools that can be used to sign the u-boot binaries, and some of those tools have more detailed explanations (and all have visible code) showing how it's done.

How to decompress LZ4 compressed u-boot

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