[PATCH v5sub3 4/4] arm64: efi: invoke EFI_RNG_PROTOCOL to supply KASLR randomness

[Matt Fleming]

On Wed, 10 Feb, at 06:55:05PM, Ard Biesheuvel wrote:
> Since arm64 does not use a decompressor that supplies an execution
> environment where it is feasible to some extent to provide a source of
> randomness, the arm64 KASLR kernel depends on the bootloader to supply
> some random bits in the /chosen/kaslr-seed DT property upon kernel entry.
> 
> On UEFI systems, we can use the EFI_RNG_PROTOCOL, if supplied, to obtain
> some random bits. At the same time, use it to randomize the offset of the
> kernel Image in physical memory.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> ---
>  arch/arm64/Kconfig                        |  5 ++
>  drivers/firmware/efi/libstub/arm-stub.c   | 40 ++++++----
>  drivers/firmware/efi/libstub/arm64-stub.c | 78 ++++++++++++++------
>  drivers/firmware/efi/libstub/fdt.c        | 14 ++++
>  4 files changed, 102 insertions(+), 35 deletions(-)

Reviewed-by: Matt Fleming <matt at codeblueprint.co.uk>