Re: pkeys: Reserve PKEY_DISABLE_READ

On Thu, Nov 08, 2018 at 06:37:41PM +0100, Florian Weimer wrote:

* Dave Hansen:

quoted

On 11/8/18 7:01 AM, Florian Weimer wrote:

quoted

Ideally, PKEY_DISABLE_READ | PKEY_DISABLE_WRITE and PKEY_DISABLE_READ |
PKEY_DISABLE_ACCESS would be treated as PKEY_DISABLE_ACCESS both, and a
line PKEY_DISABLE_READ would result in an EINVAL failure.

Sounds reasonable to me.

I don't see any urgency to do this right now.  It could easily go in
alongside the ppc patches when those get merged.

POWER support has already been merged, so we need to do something here
now, before I can complete the userspace side.

quoted

The only thing I'd suggest is that we make it something slightly
higher than 0x4.  It'll make the code easier to deal with in the
kernel if we have the ABI and the hardware mirror each other, and if
we pick 0x4 in the ABI for PKEY_DISABLE_READ, it might get messy if
the harware choose 0x4 for PKEY_DISABLE_EXECUTE or something.

So, let's make it 0x80 or something on x86 at least.

I don't have a problem with that if that's what it takes.

quoted

Also, I'll be happy to review and ack the patch to do this, but I'd
expect the ppc guys (hi Ram!) to actually put it together.

Ram, do you want to write a patch?

Florian,

	I can. But I am struggling to understand the requirement. Why is
	this needed?  Are we proposing a enhancement to the sys_pkey_alloc(),
	to be able to allocate keys that are initialied to disable-read
	only?

RP

I'll promise I finish the glibc support for this. 8-)

Thanks,
Florian

-- 
Ram Pai