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Zong Li
f83d6a730b
Wire up the flags word and the three override values in the OpenSBI firmware header. When the previous booting stage sets one of the FW_HEADER_FLAGS_OVERRIDE_A[012] bits, the cold boot path replaces the matching register with the value stored in the header before doing anything else with the boot arguments. This lets a previous booting stage which cannot pass the boot arguments in registers hand them over by patching a few words in the firmware image instead. For example, a booting stage running on a dedicated boot processor can load the OpenSBI image, patch the header with the hart id, the DTB address and, for FW_DYNAMIC, the address of a struct fw_dynamic_info it built somewhere in DRAM, and then release the hart that runs OpenSBI, without ever being able to set up that hart's registers itself. The flags word is zero in a freshly built image, so nothing is overridden and every existing booting stage keeps passing a0, a1 and a2 in registers as before. Suggested-by: Anup Patel <anup@brainfault.org> Signed-off-by: Zong Li <zong.li@sifive.com> Reviewed-by: Anup Patel <anup@brainfault.org> Link: https://lore.kernel.org/r/20260918081313.659655-3-zong.li@sifive.com Signed-off-by: Anup Patel <anup@brainfault.org>