From: David Laight <David.Laight@ACULAB.COM>
To: "'madvenka@linux.microsoft.com'" <madvenka@linux.microsoft.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 15:13:12 +0000
Message-ID: <c23de6ec47614f489943e1a89a21dfa3@AcuMS.aculab.com> (raw)
In-Reply-To: <20200728131050.24443-1-madvenka@linux.microsoft.com>
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?
If you don't care that much about performance the fixup can
all be done in userspace within the fault signal handler.
Since whatever you do needs the application changed why
not change the implementation of nested functions to not
need on-stack executable trampolines.
I can think of other alternatives that don't need much more
than an array of 'push constant; jump trampoline' instructions
be created (all jump to the same place).
You might want something to create an executable page of such
instructions.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply index
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <aefc85852ea518982e74b233e11e16d2e707bc32>
2020-07-28 13:10 ` 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 ` David Laight [this message]
2020-07-28 16:32 ` [PATCH v1 0/4] [RFC] Implement Trampoline File Descriptor Madhavan T. Venkataraman
2020-07-28 17:16 ` Andy Lutomirski
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=c23de6ec47614f489943e1a89a21dfa3@AcuMS.aculab.com \
--to=david.laight@aculab.com \
--cc=kernel-hardening@lists.openwall.com \
--cc=linux-api@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-integrity@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=madvenka@linux.microsoft.com \
--cc=oleg@redhat.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Linux-api Archive on lore.kernel.org
Archives are clonable:
git clone --mirror https://lore.kernel.org/linux-api/0 linux-api/git/0.git
# If you have public-inbox 1.1+ installed, you may
# initialize and index your mirror using the following commands:
public-inbox-init -V2 linux-api linux-api/ https://lore.kernel.org/linux-api \
linux-api@vger.kernel.org
public-inbox-index linux-api
Example config snippet for mirrors
Newsgroup available over NNTP:
nntp://nntp.lore.kernel.org/org.kernel.vger.linux-api
AGPL code for this site: git clone https://public-inbox.org/public-inbox.git