12 posts tagged u-boot, newest first.
You cannot put a filesystem's hash inside that filesystem. Two U-Boot messages that were lies — “press any key to stop autoboot” when no key worked, and quotes vanishing from the kernel command line. Four attempts, three instructive failures, and a hardware SHA engine I did not know I was using.
The hash of a filesystem cannot live inside it, so the kernel had to move somewhere signed. Then the two-command test: hand the bootloader rubbish and watch the kernel ignore it entirely. What that cost, and where the chain now ends.
You cannot sign a zImage. Why the signature goes on the FIT configuration rather than the kernel, the escape hatch that turns the whole thing into theatre, why the negative test needed two tampered images and not one, and the three ways the test lied to me.
Signing is not encrypting — the thing burned into silicon is public and you could print it on a billboard. The chicken-and-egg the 32 bytes solve, the STM32 header field by field, four locks wearing one name, and the two things I got wrong and had to correct.
The board flashed perfectly and never reached Linux. A Kconfig choice split upstream had silently retargeted my bootloader at the wrong DRAM.
NXP's uuu dies at 8% on an Apple Silicon Mac. The board's own U-Boot has ums and fastboot, and those use bulk USB, which works fine.
The signed Nerves firmware boots. And a finding that deleted an open task: enabling CONFIG_IMX_HAB wires an automatic fail-closed authentication gate into booti itself, for every kernel boot, with no bootcmd changes at all. Plus a fleet gotcha about who can SSH in.
Two fuse writes stand between a signed board and a locked one: the SRK hash, and the bit that makes the chip refuse unsigned code. Both are permanent. Here is exactly what they are, how to read their current state, and why I have not burned either.
Enabling CONFIG_IMX_HAB overflowed the SPL's SRAM budget by 10,440 bytes. Fixing that, computing the real CSF insertion offsets from the build's own binman node rather than NXP's generic one, signing with cst, and getting 'No HAB Events Found!' on hardware.
My imx-boot build failed LPDDR4 training and the gateway stopped booting before U-Boot. The cause was one Kconfig symbol. Recovering it took days, because uuu's SDP mode does not work on Apple Silicon and the board has two identical-looking micro-USB ports.
The first real build: a completely unsigned bootloader, on purpose, so that any problem is a build problem and not a signing problem. Two errors on the way, one of which is caused by a modern setuptools removing pkg_resources.
imx-boot is not one repository — it is U-Boot, ARM Trusted Firmware, NXP's imx-mkimage and the LPDDR4 training blobs, assembled together. Get one of them at the wrong version and it builds cleanly and fails to train memory. How I pinned all four using the board's own boot log.