Re: [PATCH v3 00/11] arm64: BTI kernel and vDSO support

Will Deacon
2020-05-07T14:33:42Z

On Wed, May 06, 2020 at 08:51:27PM +0100, Mark Brown wrote:
> This patch series adds support for protecting the kernel and vDSO with
> BTI including code compiled with the BPF JIT at runtime.
>
> We build the kernel with annotations for BTI and then map the kernel
> with GP based on the support on the boot CPU, rejecting secondaries that
> don't have BTI support. If there is a need to handle big.LITTLE systems
> with mismatched BTI support we will have to revisit this, currently no
> such implementations exist.
>
> This series depends on several branches in the arm64 tree:
>
> - for-next/bti-user
> - for-next/insn
> - for-next/asm
>
> v3:
> - Add a patch adding a comment about why we enable leaf support for
> PAC.
> - Fix build of the 32 bit vDSO.
> - Refactor the macro for emitting the ELF note for BTI code so that
> the flags are defined separately in order to make it easier to
> add handling for any future users.

Bugger, I'm still getting warnings (clang 11.0.1), but from an allmodconfig
build now:

warning: some functions compiled with BTI and some compiled without BTI
warning: not setting BTI in feature flags

(repeated many, many times).

I'll try to get you some more info.

Will