Date: Thu, 7 May 2015 20:11:51 +0100
From: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
To: Dave Hansen <dave@sr71.net>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH 07/12] mm: Pass the 4-bit protection key in via PROT_
 bits to syscalls
Message-ID: <20150507201151.5658faa1@lxorguk.ukuu.org.uk>
In-Reply-To: <20150507174135.FD8A0FA9@viggo.jf.intel.com>
References: <20150507174132.34AF8FAF@viggo.jf.intel.com>
	<20150507174135.FD8A0FA9@viggo.jf.intel.com>
Organization: Intel Corporation
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> diff -puN include/uapi/asm-generic/mman-common.h~pkeys-11-user-abi-bits include/uapi/asm-generic/mman-common.h
> --- a/include/uapi/asm-generic/mman-common.h~pkeys-11-user-abi-bits	2015-05-07 10:31:43.367276719 -0700
> +++ b/include/uapi/asm-generic/mman-common.h	2015-05-07 10:31:43.370276855 -0700
> @@ -10,6 +10,10 @@
>  #define PROT_WRITE	0x2		/* page can be written */
>  #define PROT_EXEC	0x4		/* page can be executed */
>  #define PROT_SEM	0x8		/* page may be used for atomic ops */
> +#define PROT_PKEY0	0x10		/* protection key value (bit 0) */
> +#define PROT_PKEY1	0x20		/* protection key value (bit 1) */
> +#define PROT_PKEY2	0x40		/* protection key value (bit 2) */
> +#define PROT_PKEY3	0x80		/* protection key value (bit 3) */

Thats leaking deep Intelisms into asm-generic which makes me very
uncomfortable. Whether we need to reserve some bits for "arch specific"
is one question, what we do with them ought not to be leaking out.

To start with trying to port code people will want to do

#define PROT_PKEY0	0
#define PROT_PKEY1	0
.. 

etc

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