[PATCH v4 3/3] arm64/efi: isolate EFI stub from the kernel proper

[Matt Fleming]

On Thu, 08 Oct, at 08:02:04PM, Ard Biesheuvel wrote:
> Since arm64 does not use a builtin decompressor, the EFI stub is built
> into the kernel proper. So far, this has been working fine, but actually,
> since the stub is in fact a PE/COFF relocatable binary that is executed
> at an unknown offset in the 1:1 mapping provided by the UEFI firmware, we
> should not be seamlessly sharing code with the kernel proper, which is a
> position dependent executable linked at a high virtual offset.
> 
> So instead, separate the contents of libstub and its dependencies, by
> putting them into their own namespace by prefixing all of its symbols
> with __efistub. This way, we have tight control over what parts of the
> kernel proper are referenced by the stub.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> ---
>  arch/arm64/kernel/Makefile            | 12 ++++-
>  arch/arm64/kernel/efi-entry.S         | 10 ++--
>  arch/arm64/kernel/head.S              | 14 ++---
>  arch/arm64/kernel/image.h             | 27 ++++++++++
>  drivers/firmware/efi/libstub/Makefile | 39 +++++++++++---
>  drivers/firmware/efi/libstub/string.c | 57 ++++++++++++++++++++
>  6 files changed, 139 insertions(+), 20 deletions(-)

Reviewed-by: Matt Fleming <matt.fleming at intel.com>

-- 
Matt Fleming, Intel Open Source Technology Center