Re: [PATCH v10 23/40] arm64/signal: Set up and restore the GCS context for signal handlers

Catalin Marinas
2024-08-21T18:18:14Z

On Wed, Aug 21, 2024 at 07:03:13PM +0100, Mark Brown wrote:
> On Wed, Aug 21, 2024 at 06:28:49PM +0100, Catalin Marinas wrote:
> > On Thu, Aug 01, 2024 at 01:06:50PM +0100, Mark Brown wrote:
> > > + /*
> > > + * Push a cap and the GCS entry for the trampoline onto the GCS.
> > > + */
> > > + put_user_gcs((unsigned long)sigtramp, gcspr_el0 - 2, &ret);
> > > + put_user_gcs(GCS_SIGNAL_CAP(gcspr_el0 - 1), gcspr_el0 - 1, &ret);
> > > + if (ret != 0)
> > > + return ret;
>
> > Doesn't the second put_user_gcs() override the previous ret?
>
> No, we only set ret on error - if the first one faults it'll set ret
> then the second one will either leave it unchanged or write the same
> error code depending on if it fails. This idiom is used quite a lot in
> the signal code.

You are right, I missed that it's called 'err' in put_user_gcs(),
thought it's overridden.

--
Catalin