Re: [RFC][PATCH 1/6] x86: Annotate _THIS_IP_

Josh Poimboeuf
2021-11-24T18:18:34Z

On Tue, Nov 23, 2021 at 03:14:45PM +0100, Peter Zijlstra wrote:
> On Tue, Nov 23, 2021 at 01:53:49PM +0000, Mark Rutland wrote:
> > On Mon, Nov 22, 2021 at 06:03:02PM +0100, Peter Zijlstra wrote:
> > > In order to find _THIS_IP_ code references in objtool, annotate them.
> >
> > Just to check my understanding, IIUC this is because in later patches
> > you'll look at text relocations to spot missing ENDBRs, and when doing
> > so you need to filter out _THIS_IP_ instances, since those don't need an
> > ENDBR. Is that right?
> >
> > Just checking I haven't missed some other concern that might apply to
> > arm64's BTI (Branch Target Identifier), which are analagous to ENDBR.
>
> Correct; since _THIS_IP_ is never used for control flow (afaik, let's
> hope to $deity etc..) we can ignore any relocation resulting from it
> (lots!).

This would all be good context to add to the commit message.

--
Josh