Re: [PATCH v26 0/9] Control-flow Enforcement: Indirect Branch Tracking

[H.J. Lu]

On Wed, Apr 28, 2021 at 7:52 AM Andy Lutomirski <luto@xxxxxxxxxx> wrote:
>
> On Wed, Apr 28, 2021 at 7:48 AM David Laight <David.Laight@xxxxxxxxxx> wrote:
> >
> > From: Yu-cheng Yu
> > > Sent: 27 April 2021 21:47
> > >
> > > Control-flow Enforcement (CET) is a new Intel processor feature that blocks
> > > return/jump-oriented programming attacks.  Details are in "Intel 64 and
> > > IA-32 Architectures Software Developer's Manual" [1].
> > ...
> >
> > Does this feature require that 'binary blobs' for out of tree drivers
> > be compiled by a version of gcc that adds the ENDBRA instructions?
> >
> > If enabled for userspace, what happens if an old .so is dynamically
> > loaded?

CET will be disabled by ld.so in this case.

> > Or do all userspace programs and libraries have to have been compiled
> > with the ENDBRA instructions?

Correct.  ld and ld.so check this.

> If you believe that the userspace tooling for the legacy IBT table
> actually works, then it should just work.  Yu-cheng, etc: how well
> tested is it?
>

Legacy IBT bitmap isn't unused since it doesn't cover legacy codes
generated by legacy JITs.

-- 
H.J.