linux-kernel - Re: [PATCH 1/5] x86/vm86: Move userspace accesses to do_sys

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Date:	Mon, 13 Jul 2015 12:45:32 -0400
From:	Brian Gerst <brgerst@...il.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 1/5] x86/vm86: Move userspace accesses to do_sys_vm86()

On Sat, Jul 11, 2015 at 12:37 PM, Andy Lutomirski <luto@...capital.net> wrote:
> On Fri, Jul 10, 2015 at 10:09 PM, Brian Gerst <brgerst@...il.com> wrote:
>> Move the userspace accesses down into the common function in
>> preparation for the next set of patches.
>>
>
> One thing I don't like about the current code that makes these patches
> harder to review is the bizarre approach to copying.  If you changed
> this:
>
>> -       tmp = copy_vm86_regs_from_user(&info.regs, &v86->regs,
>> -                                      offsetof(struct kernel_vm86_struct, vm86plus) -
>> -                                      sizeof(info.regs));
>
> into a normal field-by-field get_user / copy_from_user (the latter for
> the big regs struct) then it would be clear what the ABI is and it
> would be much easier to read the patches and confirm that you aren't
> accidentally changing the ABI.
>
> You could also get rid of the constraint that certain fields in
> apparently kernel-internal structs had to be in a certain order.
>
> Other than that, patches 1-4 look good on cursory inspection.  I'll
> look more carefully later.  I need to think about patch 5 more.
>
> --Andy

Any other comments before I start working on v2?

--
Brian Gerst
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