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Re: Support for Intel X1000
- From: Florian Weimer <fweimer at redhat dot com>
- To: "Kinsella, Ray" <ray dot kinsella at intel dot com>, "dalias at libc dot org" <dalias at libc dot org>
- Cc: "carlos at redhat dot com" <carlos at redhat dot com>, "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>
- Date: Wed, 20 May 2015 16:54:28 +0200
- Subject: Re: Support for Intel X1000
- Authentication-results: sourceware.org; auth=none
- References: <1431426490 dot 3246 dot 29 dot camel at intel dot com> <5552104C dot 1020806 at redhat dot com> <20150512152207 dot GW17573 at brightrain dot aerifal dot cx> <1431513937 dot 2622 dot 24 dot camel at intel dot com> <20150513170809 dot GY17573 at brightrain dot aerifal dot cx> <555397D0 dot 70808 at redhat dot com> <20150515012433 dot GC17573 at brightrain dot aerifal dot cx> <1432130053 dot 17726 dot 6 dot camel at intel dot com>
On 05/20/2015 03:54 PM, Kinsella, Ray wrote:
>
>> I did a little bit of research and it appears that only lock-prefixed
>> instructions which can page fault are affected by this bug. So why not
>> just make the kernel enforce mlockall for all processes on affected
>> cpus?
>
> mlockall doesn't help in situations where a page is marked as CoW, you
> still get the page fault on write (i.e. lock cmpxchg -
> read/modify/write).
> I am seeing this in two places :-
> 1. when the data section of an elf binary is loaded.
> 2. memory shared between a child and a parent process after a fork.
What kind of bug are we talking about? Does the CPU hang if the
conditions are triggered? Or a GP exception the kernel can handle in
some way?
--
Florian Weimer / Red Hat Product Security