From: Andy Lutomirski <luto@kernel.org>
To: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
Cc: David Laight <David.Laight@aculab.com>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
"linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
"linux-integrity@vger.kernel.org"
<linux-integrity@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-security-module@vger.kernel.org"
<linux-security-module@vger.kernel.org>,
"oleg@redhat.com" <oleg@redhat.com>,
"x86@kernel.org" <x86@kernel.org>
Subject: Re: [PATCH v1 0/4] [RFC] Implement Trampoline File Descriptor
Date: Tue, 28 Jul 2020 10:16:32 -0700 [thread overview]
Message-ID: <CALCETrUta5-0TLJ9-jfdehpTAp2Efmukk2npYadFzz9ozOrG2w@mail.gmail.com> (raw)
In-Reply-To: <f5cfd11b-04fe-9db7-9d67-7ee898636edb@linux.microsoft.com>
On Tue, Jul 28, 2020 at 9:32 AM Madhavan T. Venkataraman
<madvenka@linux.microsoft.com> wrote:
>
> Thanks. See inline..
>
> On 7/28/20 10:13 AM, David Laight wrote:
> > From: madvenka@linux.microsoft.com
> >> Sent: 28 July 2020 14:11
> > ...
> >> The kernel creates the trampoline mapping without any permissions. When
> >> the trampoline is executed by user code, a page fault happens and the
> >> kernel gets control. The kernel recognizes that this is a trampoline
> >> invocation. It sets up the user registers based on the specified
> >> register context, and/or pushes values on the user stack based on the
> >> specified stack context, and sets the user PC to the requested target
> >> PC. When the kernel returns, execution continues at the target PC.
> >> So, the kernel does the work of the trampoline on behalf of the
> >> application.
> > Isn't the performance of this going to be horrid?
>
> It takes about the same amount of time as getpid(). So, it is
> one quick trip into the kernel. I expect that applications will
> typically not care about this extra overhead as long as
> they are able to run.
What did you test this on? A page fault on any modern x86_64 system
is much, much, much, much slower than a syscall.
--Andy
next prev parent reply other threads:[~2020-07-28 17:16 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <aefc85852ea518982e74b233e11e16d2e707bc32>
2020-07-28 13:10 ` [PATCH v1 0/4] [RFC] Implement Trampoline File Descriptor madvenka
2020-07-28 13:10 ` [PATCH v1 1/4] [RFC] fs/trampfd: Implement the trampoline file descriptor API madvenka
2020-07-28 14:50 ` Oleg Nesterov
2020-07-28 14:58 ` Madhavan T. Venkataraman
2020-07-28 16:06 ` Oleg Nesterov
2020-07-28 13:10 ` [PATCH v1 2/4] [RFC] x86/trampfd: Provide support for the trampoline file descriptor madvenka
2020-07-30 9:06 ` Greg KH
2020-07-30 14:25 ` Madhavan T. Venkataraman
2020-07-28 13:10 ` [PATCH v1 3/4] [RFC] arm64/trampfd: " madvenka
2020-07-28 13:10 ` [PATCH v1 4/4] [RFC] arm/trampfd: " madvenka
2020-07-28 15:13 ` [PATCH v1 0/4] [RFC] Implement Trampoline File Descriptor David Laight
2020-07-28 16:32 ` Madhavan T. Venkataraman
2020-07-28 17:16 ` Andy Lutomirski [this message]
2020-07-28 18:52 ` Madhavan T. Venkataraman
2020-07-29 8:36 ` David Laight
2020-07-29 17:55 ` Madhavan T. Venkataraman
[not found] ` <81d744c0-923e-35ad-6063-8b186f6a153c@linux.microsoft.com>
2020-07-29 5:16 ` Andy Lutomirski
2020-07-28 16:05 ` Casey Schaufler
2020-07-28 16:49 ` Madhavan T. Venkataraman
2020-07-28 17:05 ` James Morris
2020-07-28 17:08 ` Madhavan T. Venkataraman
2020-07-28 17:31 ` Andy Lutomirski
2020-07-28 19:01 ` Madhavan T. Venkataraman
2020-07-29 13:29 ` Florian Weimer
2020-07-30 13:09 ` David Laight
2020-08-02 11:56 ` Pavel Machek
2020-08-03 8:08 ` David Laight
2020-08-03 15:57 ` Madhavan T. Venkataraman
2020-07-30 14:42 ` Madhavan T. Venkataraman
[not found] ` <6540b4b7-3f70-adbf-c922-43886599713a@linux.microsoft.com>
2020-07-30 20:54 ` Andy Lutomirski
2020-07-31 17:13 ` Madhavan T. Venkataraman
2020-07-31 18:31 ` Mark Rutland
2020-08-03 8:27 ` David Laight
2020-08-03 16:03 ` Madhavan T. Venkataraman
2020-08-03 16:57 ` David Laight
2020-08-03 17:00 ` Madhavan T. Venkataraman
2020-08-03 17:58 ` Madhavan T. Venkataraman
2020-08-04 13:55 ` Mark Rutland
2020-08-04 14:33 ` David Laight
2020-08-04 14:44 ` David Laight
2020-08-04 14:48 ` Madhavan T. Venkataraman
2020-08-04 15:46 ` Madhavan T. Venkataraman
2020-08-02 13:57 ` Florian Weimer
2020-08-02 18:54 ` Madhavan T. Venkataraman
2020-08-02 20:00 ` Andy Lutomirski
2020-08-02 22:58 ` Madhavan T. Venkataraman
2020-08-03 18:36 ` Madhavan T. Venkataraman
2020-08-10 17:34 ` Madhavan T. Venkataraman
2020-08-11 21:12 ` Madhavan T. Venkataraman
2020-08-03 8:23 ` David Laight
2020-08-03 15:59 ` Madhavan T. Venkataraman
2020-07-31 18:09 ` Mark Rutland
2020-07-31 20:08 ` Madhavan T. Venkataraman
2020-08-03 16:57 ` Madhavan T. Venkataraman
2020-08-04 14:30 ` Mark Rutland
2020-08-06 17:26 ` Madhavan T. Venkataraman
2020-08-08 22:17 ` Pavel Machek
2020-08-11 12:41 ` Madhavan T. Venkataraman
2020-08-11 13:08 ` Pavel Machek
2020-08-11 15:54 ` Madhavan T. Venkataraman
2020-08-12 10:06 ` Mark Rutland
2020-08-12 18:47 ` Madhavan T. Venkataraman
2020-08-19 18:53 ` Mickaël Salaün
2020-09-01 15:42 ` Mark Rutland
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