linux-kernel - RE: [PATCH v8 1/3] x86: Expand exception table to allow new handling options

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Date:	Mon, 11 Jan 2016 23:48:12 +0000
From:	"Luck, Tony" <tony.luck@...el.com>
To:	Brian Gerst <brgerst@...il.com>,
	Andy Lutomirski <luto@...capital.net>
CC:	"Williams, Dan J" <dan.j.williams@...el.com>,
	Borislav Petkov <bp@...en8.de>, X86 ML <x86@...nel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Robert <elliott@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-nvdimm <linux-nvdimm@...1.01.org>
Subject: RE: [PATCH v8 1/3] x86: Expand exception table to allow new
 handling options

> I agree that for at least put_user() using asm goto would be an even
> better option.  get_user() on the other hand, will be much messier to
> deal with, since asm goto statements can't have outputs, plus it
> zeroes the output register on fault.

get_user() is the much more interesting one for me. A read from
a poisoned user address that generates a machine check is something
that can be recovered (kill the process).  A write to user space doesn't
even generate a machine check.

-Tony