linux-kernel - Re: [RFC PATCH] x86 NMI-safe INT3 and Page Fault (v5)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 21 Apr 2008 13:59:27 -0400
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Mathieu Desnoyers <compudj@...stal.dyndns.org>
CC:	Pavel Machek <pavel@....cz>, mingo@...e.hu, akpm@...l.org,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Frank Ch. Eigler" <fche@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] x86 NMI-safe INT3 and Page Fault (v5)

Mathieu Desnoyers wrote:
> * H. Peter Anvin (hpa@...or.com) wrote:
>> Pavel Machek wrote:
>>>> There is also the page fault case. I think putting this test in
>>>> ret_from_exception would be both safe (it is executed for any
>>>> exception return) and fast (exceptions are rare).
>>> Eh? I thought that page fault is one of the hottest paths in kernel
>>> (along with syscall and packet receive/send)...
>>> 								Pavel
> 
> On x86_64, we can pinpoint only the page faults returning to the kernel,
> which are rare and only caused by vmalloc accesses. Ideally we could do
> the same on x86_32.
> 

Pinpoint, how?  Ultimately you need a runtime test, and you better be 
showing that people are going to die unless before you add a cycle to 
the page fault path.  I'm only slightly exaggerating that.

	-hpa

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/