linux-kernel - Re: [PATCH 3/6] intel_sgx: driver for Intel Secure Guard eXtensions

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Date:	Wed, 27 Apr 2016 16:32:23 -0700
From:	Jethro Beekman <kernel@...ekman.nl>
To:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:	gregkh@...uxfoundation.org,
	"open list:STAGING SUBSYSTEM" <devel@...verdev.osuosl.org>,
	"maintainer:X86 ARCHITECTURE 32-BIT AND 64-BIT" <x86@...nel.org>,
	"open list:X86 ARCHITECTURE 32-BIT AND 64-BIT" 
	<linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 3/6] intel_sgx: driver for Intel Secure Guard eXtensions

On 27-04-16 05:40, Jarkko Sakkinen wrote:
>> The hardware supports calling EEXTEND on only a part of a page, I think the
>> driver should also support that.
>
> Why would you want to do that?

You might have segments in a binary that don't start at the beginning of a page
or that end before the end of a page. For example:

  Type           Offset             VirtAddr           PhysAddr
                 FileSiz            MemSiz              Flags  Align
  LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x000000000001bcac 0x000000000001bcac  R E    1000
  LOAD           0x000000000001c8e8 0x000000000001c8e8 0x000000000001c8e8
                 0x0000000000000790 0x0000000000000c68  RW     1000

There's no need to measure the extra padding (0x1bd00--0x1c7ff and
0x1cb00--0x1cfff) in this case.

> /Jarkko

Jethro