linux-kernel - Re: [RFC PATCH] x86, entry: Switch stacks on a paranoid entry from userspace

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Message-ID: <20141118161259.GC5238@pd.tnic>
Date:	Tue, 18 Nov 2014 17:12:59 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	"Luck, Tony" <tony.luck@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [RFC PATCH] x86, entry: Switch stacks on a paranoid entry from
 userspace

On Mon, Nov 17, 2014 at 12:05:59PM -0800, Andy Lutomirski wrote:
> https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/log/?h=x86/paranoid
> 
> I'm not quite ready to send v3.  I want to do two things first:
> 
> 1. Consider disabling the stack switch for double_fault.

Sounds conservatively nice :)

> 2. Clean up the macros.  I'll validate this by ensuring that the
> generated code is identical to the current version.
> 
> IOW, I don't expect the asm for machine_check to change.

Right, so I don't see anything wrong with the patch but entry_64.S is
nasty so don't take my word for it.

I guess handlers should need to do "if (user_mode_vm(regs))" after your
change now, in order to know what to do.

I'll try to do some error injection here too, on my boxes to see how
this behaves.

Thanks.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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