[PATCH v4 2/2] arm64: Introduce HWCAPS2_EXECONLY

[Will Deacon]

On Fri, Mar 26, 2021 at 09:35:53AM +0000, Catalin Marinas wrote:
> On Thu, Mar 25, 2021 at 07:00:00PM +0000, Will Deacon wrote:
> > On Fri, Mar 12, 2021 at 05:38:11PM +0000, Vladimir Murzin wrote:
> > > With EPAN supported it might be handy to user know that PROT_EXEC
> > > gives execute-only permission, so advertise it via HWCAPS2_EXECONLY
> > > 
> > > Cc: Kees Cook <keescook at chromium.org>
> > > Cc: Catalin Marinas <catalin.marinas at arm.com>
> > > Signed-off-by: Vladimir Murzin <vladimir.murzin at arm.com>
> > > ---
> > >  arch/arm64/include/asm/hwcap.h      | 1 +
> > >  arch/arm64/include/asm/sysreg.h     | 1 +
> > >  arch/arm64/include/uapi/asm/hwcap.h | 1 +
> > >  arch/arm64/kernel/cpufeature.c      | 3 +++
> > >  arch/arm64/kernel/cpuinfo.c         | 1 +
> > >  5 files changed, 7 insertions(+)
> > 
> > I still don't see the need for this patch. Can we avoid merging it until
> > somebody has a use for it, please?
> 
> It's more about telling user-space that the feature is present though we
> didn't do this last time we had exec-only permissions either. I was
> hoping we can do better this time. OTOH, probably no-one will check for
> this HWCAP anyway, so let's wait until someone asks for it.

Yes, that's what I mean by "somebody has a use for it" -- I don't understand
what userspace would do with this and it's certainly not using it now.

Will