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Date: Fri, 18 Dec 2015 15:08:50 -0800
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Subject: Re: Rethinking sigcontext's xfeatures slightly for PKRU's benefit?
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Oleg Nesterov <oleg@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
        Borislav Petkov <bp@alien8.de>, Brian Gerst <brgerst@gmail.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Christoph Hellwig <hch@lst.de>
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On Fri, Dec 18, 2015 at 2:28 PM, Andy Lutomirski <luto@amacapital.net> wrote:
>
> Apps that don't want to use the baseline_pkru mechanism could use
> syscalls to claim ownership of protection keys but then manage them
> purely with WRPKRU directly.  We could optionally disallow
> mprotect_key on keys that weren't allocated in advance.
>
> Does that seem sane?

So everything seems sane except for the need for that baseline_pkru.

I'm not seeing why it couldn't just be a fixed value. Is there any
real downside to it?

                    Linus