Re: [RFC PATCH] rseq: x86: implement abort-at-ip extension

----- On Jan 12, 2022, at 11:00 AM, Florian Weimer fw@deneb.enyo.de wrote:

* Peter Zijlstra:

quoted

On Wed, Jan 12, 2022 at 04:16:36PM +0100, Florian Weimer wrote:

quoted

You could perhaps push a signal frame onto the stack.  It's going to
be expensive, but it's already in the context switch path, so maybe it
does not matter.

Please no! Signals are a trainwreck that need change (see the whole
AVX-512 / AMX saga), we shouldn't use more of that just cause.

If it's a signal, it should be modeled as such.  I think it's pretty
close to a synchronous signal.

Florian, just to validate here: is your argument about AVX-512/AMX or about
rseq abort-at-ip ?

Am I understanding correctly that you would prefer that the kernel push an entire
signal frame onto the stack rather than just push the abort-at-ip value
on abort ? If it is the case, are there advantages in doing so ? Tooling support ?

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com