efi/libstub: Use relocated version of kernel's struct screen_info
authorArd Biesheuvel <ardb@kernel.org>
Wed, 22 Mar 2023 00:11:18 +0000 (01:11 +0100)
committerArd Biesheuvel <ardb@kernel.org>
Thu, 23 Mar 2023 11:27:18 +0000 (12:27 +0100)
commitfc3608aaa5751318837e4bbe0282b3836bca5080
tree0d769d09c9b4f11a52e1d7d87e59ea738375e67f
parent97fd768e501fd5d377cb0bf46a35bad2cd21c153
efi/libstub: Use relocated version of kernel's struct screen_info

In some cases, we expose the kernel's struct screen_info to the EFI stub
directly, so it gets populated before even entering the kernel.  This
means the early console is available as soon as the early param parsing
happens, which is nice. It also means we need two different ways to pass
this information, as this trick only works if the EFI stub is baked into
the core kernel image, which is not always the case.

Huacai reports that the preparatory refactoring that was needed to
implement this alternative method for zboot resulted in a non-functional
efifb earlycon for other cases as well, due to the reordering of the
kernel image relocation with the population of the screen_info struct,
and the latter now takes place after copying the image to its new
location, which means we copy the old, uninitialized state.

So let's ensure that the same-image version of alloc_screen_info()
produces the correct screen_info pointer, by taking the displacement of
the loaded image into account.

Reported-by: Huacai Chen <chenhuacai@loongson.cn>
Tested-by: Huacai Chen <chenhuacai@loongson.cn>
Link: https://lore.kernel.org/linux-efi/20230310021749.921041-1-chenhuacai@loongson.cn/
Fixes: 42c8ea3dca094ab8 ("efi: libstub: Factor out EFI stub entrypoint into separate file")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
drivers/firmware/efi/libstub/arm64-stub.c
drivers/firmware/efi/libstub/efi-stub-entry.c
drivers/firmware/efi/libstub/efi-stub.c
drivers/firmware/efi/libstub/efistub.h
drivers/firmware/efi/libstub/screen_info.c
drivers/firmware/efi/libstub/zboot.c