Re: [PATCH v2] arm64/signal: Silence sparse warning storing GCSPR_EL0

[Mark Brown <broonie@kernel.org>]

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On Fri, Dec 13, 2024 at 04:26:40PM +0000, Catalin Marinas wrote:
> On Wed, Dec 11, 2024 at 01:00:35AM +0000, Mark Brown wrote:

> > -static bool gcs_signal_cap_valid(u64 addr, u64 val)
> > +static bool gcs_signal_cap_valid(unsigned long __user *addr, u64 val)
> >  {
> >  	return val == GCS_SIGNAL_CAP(addr);
> >  }

> Another personal preference - addresses should be (unsigned long),
> pointer to be accessed (... __user *). But we could even scrap this
> function, there's a single caller to a one-line function.

I'm not sure I follow what you're saying here - the pointer here is an
unsigned long __user *?  The value in val is not a pointer or address,
it's a cap value derived from a pointer.  But yeah, we could inline and
render it moot.

> > -	write_sysreg_s(gcspr_el0 + 1, SYS_GCSPR_EL0);
> > +	write_sysreg_s((__force u64)(gcspr_el0 + 1), SYS_GCSPR_EL0);

> Looking through the code, do we have a similar problem in
> gcs_signal_entry()? Or do we rely on sparse ignoring (unsigned long)
> casts?

> Whichever way we go, I think we should have consistency between these
> two functions.

It's not coming up since there's a cast to unsigned long in there which
sparse likes, I can adjust that to a cast to __force u64 in there since
people didn't seem to like the cast to unsigned long.

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