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Subject: Re: [PATCH] mm: only enable sys_pkey* when ARCH_HAS_PKEYS
To: Heiko Carstens <heiko.carstens@de.ibm.com>,
        Russell King - ARM Linux <linux@armlinux.org.uk>
References: <1477958904-9903-1-git-send-email-mark.rutland@arm.com>
 <c716d515-409f-4092-73d2-1a81db6c1ba3@linux.intel.com>
 <20161104234459.GA18760@remoulade> <20161108093042.GC3528@osiris>
 <20161108104112.GM1041@n2100.armlinux.org.uk> <20161108112400.GE3528@osiris>
Cc: Mark Rutland <mark.rutland@arm.com>, linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Mel Gorman <mgorman@techsingularity.net>,
        Thomas Gleixner <tglx@linutronix.de>, linux-api@vger.kernel.org,
        linux-arch@vger.kernel.org, linux-mm@kvack.org,
        torvalds@linux-foundation.org
From: Dave Hansen <dave.hansen@linux.intel.com>
Message-ID: <c4d177e7-c707-93aa-20be-5959d5193655@linux.intel.com>
Date: Tue, 8 Nov 2016 10:39:04 -0800
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On 11/08/2016 03:24 AM, Heiko Carstens wrote:
> Something like this:
> 
> diff --git a/mm/mprotect.c b/mm/mprotect.c
> index 11936526b08b..9fb86b107e49 100644
> --- a/mm/mprotect.c
> +++ b/mm/mprotect.c
> @@ -484,6 +484,8 @@ SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
>  	return do_mprotect_pkey(start, len, prot, -1);
>  }
>  
> +#ifdef CONFIG_ARCH_HAS_PKEYS
> +
>  SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len,
>  		unsigned long, prot, int, pkey)
>  {
> @@ -534,3 +536,4 @@ SYSCALL_DEFINE1(pkey_free, int, pkey)
>  	 */
>  	return ret;
>  }
> +#endif /* CONFIG_ARCH_HAS_PKEYS */

That's fine with me, fwiw.  It ends up meaning that the config option
changes whether we get -ENOSPC vs. -ENOSYS, so the x86_32 behavior will
change, for instance.  But, I _think_ that's OK.