From: Josh Poimboeuf <jpoimboe@redhat.com>
To: David Laight <David.Laight@ACULAB.COM>
Cc: "'kpark3469@gmail.com'" <kpark3469@gmail.com>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
"keescook@chromium.org" <keescook@chromium.org>,
"will.deacon@arm.com" <will.deacon@arm.com>,
"mark.rutland@arm.com" <mark.rutland@arm.com>,
"james.morse@arm.com" <james.morse@arm.com>,
"keun-o.park@darkmatter.ae" <keun-o.park@darkmatter.ae>,
"psodagud@codeaurora.org" <psodagud@codeaurora.org>,
"mingo@kernel.org" <mingo@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 3/3] x86: usercopy: reimplement arch_within_stack_frames with unwinder
Date: Tue, 10 Apr 2018 10:35:38 -0500 [thread overview]
Message-ID: <20180410153500.shqpjemlsfp63yu5@treble> (raw)
In-Reply-To: <a59b818d84b74c13a4f25f757eba1f93@AcuMS.aculab.com>
On Mon, Apr 09, 2018 at 01:14:58PM +0000, David Laight wrote:
> From: kpark3469@gmail.com
> > Sent: 09 April 2018 12:59
> >
> > The old arch_within_stack_frames which used the frame pointer is
> > now reimplemented to use frame pointer unwinder apis. So the main
> > functionality is same as before.
>
> How much slower does this make the code?
> Following stack frames using %bp is reasonably quick.
> I can't imagine some of the other unwinder APIs being any where
> near that fast.
> While fine for fault tracebacks, using them during usercopy
> is likely to have measurable performance impact.
Agreed, using the unwind interface is going to be quite a bit slower
than the current manual approach. So this patch has only drawbacks and
no benefits.
The only benefit would be if you used the unwind API in a generic
manner, such that it also worked for the ORC unwinder. But even then I
think we'd need to see performance numbers, with both FP and ORC, to see
how bad the impact is on usercopy.
--
Josh
next prev parent reply other threads:[~2018-04-10 15:35 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-09 11:59 [PATCH v3 0/3] usercopy: reimplement arch_within_stack_frames kpark3469
2018-04-09 11:59 ` [PATCH v3 1/3] stacktrace: move arch_within_stack_frames from thread_info.h kpark3469
2018-04-09 11:59 ` [PATCH v3 2/3] arm64: usercopy: implement arch_within_stack_frames kpark3469
2018-04-09 11:59 ` [PATCH v3 3/3] x86: usercopy: reimplement arch_within_stack_frames with unwinder kpark3469
2018-04-09 13:14 ` David Laight
2018-04-10 15:35 ` Josh Poimboeuf [this message]
2018-04-09 21:03 ` [PATCH v3 1/3] stacktrace: move arch_within_stack_frames from thread_info.h kbuild test robot
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