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Subject: Re: [PATCH 4/9] x86, pkeys: override pkey when moving away from
 PROT_EXEC
To:     Ram Pai <linuxram@us.ibm.com>
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Cc:     Dave Hansen <dave.hansen@linux.intel.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        shakeelb@google.com, stable@kernel.org, tglx@linutronix.de,
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        shuah@kernel.org
From:   Dave Hansen <dave.hansen@intel.com>
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Date:   Thu, 26 Apr 2018 10:57:31 -0700
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On 04/06/2018 06:09 PM, Ram Pai wrote:
> Well :). my point is add this code and delete the other
> code that you add later in that function.

I don't think I'm understanding what your suggestion was.  I looked at
the code and I honestly do not think I can remove any of it.

For the plain (non-explicit pkey_mprotect()) case, there are exactly
four paths through __arch_override_mprotect_pkey(), resulting in three
different results.

1. New prot==PROT_EXEC, no pkey-exec support -> do not override
2. New prot!=PROT_EXEC, old VMA not PROT_EXEC-> do not override
3. New prot==PROT_EXEC, w/ pkey-exec support -> override to exec pkey
4. New prot!=PROT_EXEC, old VMA is PROT_EXEC -> override to default

I don't see any redundancy there, or any code that we can eliminate or
simplify.  It was simpler before, but that's what where bug was.