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

Will Deacon
2020-05-07T14:35:56Z

On Thu, May 07, 2020 at 03:33:32PM +0100, Will Deacon wrote:
> 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.

Quick look at the log suggests that these are caused by HDRTEST, whatever
that is.

Will