grub: embed per-SoC cmdline in efi.bin, keep rootfs generic - #231
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Phanendra Yarra (phanendra-qc) wants to merge 1 commit into
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grub: embed per-SoC cmdline in efi.bin, keep rootfs generic#231Phanendra Yarra (phanendra-qc) wants to merge 1 commit into
Phanendra Yarra (phanendra-qc) wants to merge 1 commit into
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Board-specific kernel parameters (e.g. arm64.nopauth for RB4) are now
carried by each board's BOOTAA64.EFI rather than baked into the rootfs
grub.cfg or resolved at runtime by a userspace service.
Problem with the previous approach
-----------------------------------
The earlier design used two grub.cfg menu entries (Generic / RB4) and a
grub-soc-select.service that ran at sysinit, read the Device Tree serial
number, and called grub-set-default to pick the right entry for the next
boot. This worked but had two drawbacks:
- The rootfs was not fully board-agnostic: it contained the RB4 menu
entry, grub-soc-map.conf, and the runtime selection service.
- The correct cmdline only took effect from the second boot (the service
runs after the kernel is already up).
New design: soc_extra_cmdline GRUB variable
-------------------------------------------
The ESP (efi.bin) is already per-board in gen-flash-dirs.sh (sector size,
VolatileVars.bin). BOOTAA64.EFI already embeds a bootstrap grub.cfg via
grub-mkstandalone. That bootstrap config is the natural place to carry
board identity — it is evaluated at GRUB stage, before the kernel loads,
and GRUB variables set there survive the configfile jump into the rootfs
grub.cfg.
build-efi-esp.sh --extra-cmdline "arm64.nopauth" → rb4/efi.bin
build-efi-esp.sh → generic/efi.bin
build-rootfs.sh → rootfs.img (shared)
Bootstrap config (baked into BOOTAA64.EFI):
set soc_extra_cmdline="arm64.nopauth" # RB4
set soc_extra_cmdline="" # generic
configfile ($root)/boot/grub/grub.cfg
rootfs grub.cfg linux line (single generic entry):
linux /boot/vmlinuz-... <base_cmdline> ${soc_extra_cmdline}
GRUB expands ${soc_extra_cmdline} at runtime from the bootstrap value.
The rootfs image is identical for all boards.
Changes
-------
bootloader/build-efi-esp.sh
- Add --extra-cmdline <params> argument (default empty).
- Embed 'set soc_extra_cmdline="<value>"' in the bootstrap config
written into BOOTAA64.EFI by grub-mkstandalone.
rootfs/scripts/build-rootfs.sh
- GRUB_DEFAULT reverted to 0 (single entry, no grubenv needed).
- Remove Step 7.6 (grub-soc-map.conf generation).
- Replace Step 9.4 (RB4 entry injection) with a sed pass that appends
'${soc_extra_cmdline}' to every linux line in grub.cfg.
flash/gen-flash-dirs.sh
- Read extra_cmdline from each board's JSON entry.
- When non-empty, rebuild efi.bin for that board via build-efi-esp.sh
--extra-cmdline before placing it in the flash directory.
boards.json example
-------------------
{ "name": "rb4", "ptool_platform": "qrb4210-rb2",
"extra_cmdline": "arm64.nopauth" }
{ "name": "rb5", "ptool_platform": "qrb5165-rb5" }
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Board-specific kernel parameters (e.g. arm64.nopauth for RB4) are now carried by each board's BOOTAA64.EFI rather than baked into the rootfs grub.cfg or resolved at runtime by a userspace service.
Design: soc_extra_cmdline GRUB variable
The ESP (efi.bin) is already per-board in gen-flash-dirs.sh (sector size, VolatileVars.bin). BOOTAA64.EFI already embeds a bootstrap grub.cfg via grub-mkstandalone. That bootstrap config is the natural place to carry board identity — it is evaluated at GRUB stage, before the kernel loads, and GRUB variables set there survive the configfile jump into the rootfs grub.cfg.
build-efi-esp.sh --extra-cmdline "arm64.nopauth" → rb4/efi.bin
build-efi-esp.sh → generic/efi.bin
build-rootfs.sh → rootfs.img (shared)
Bootstrap config (baked into BOOTAA64.EFI):
set soc_extra_cmdline="arm64.nopauth" # RB4
set soc_extra_cmdline="" # generic
configfile ($root)/boot/grub/grub.cfg
rootfs grub.cfg linux line (single generic entry):
linux /boot/vmlinuz-... <base_cmdline> ${soc_extra_cmdline}
GRUB expands ${soc_extra_cmdline} at runtime from the bootstrap value. The rootfs image is identical for all boards.
Changes
bootloader/build-efi-esp.sh
rootfs/scripts/build-rootfs.sh
flash/gen-flash-dirs.sh
boards.json example
{ "name": "rb4", "ptool_platform": "qrb4210-rb2",
"extra_cmdline": "arm64.nopauth" } { "name": "rb5", "ptool_platform": "qrb5165-rb5" }