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 [thread overview] 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)
WARNING: multiple messages have this Message-ID (diff)
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 [thread overview] 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) _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-07-28 15:14 UTC|newest] Thread overview: 146+ 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 ` madvenka 2020-07-28 13:10 ` [PATCH v1 1/4] [RFC] fs/trampfd: Implement the trampoline file descriptor API madvenka 2020-07-28 13:10 ` madvenka 2020-07-28 14:50 ` Oleg Nesterov 2020-07-28 14:50 ` Oleg Nesterov 2020-07-28 14:58 ` Madhavan T. Venkataraman 2020-07-28 14:58 ` Madhavan T. Venkataraman 2020-07-28 16:06 ` Oleg Nesterov 2020-07-28 16:06 ` Oleg Nesterov 2020-07-28 19:48 ` kernel test robot 2020-07-29 2:33 ` kernel test robot 2020-07-28 13:10 ` [PATCH v1 2/4] [RFC] x86/trampfd: Provide support for the trampoline file descriptor madvenka 2020-07-28 13:10 ` madvenka 2020-07-28 18:38 ` kernel test robot 2020-07-30 9:06 ` Greg KH 2020-07-30 9:06 ` Greg KH 2020-07-30 14:25 ` Madhavan T. Venkataraman 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 ` madvenka 2020-07-28 13:10 ` [PATCH v1 4/4] [RFC] arm/trampfd: " madvenka 2020-07-28 13:10 ` madvenka 2020-07-28 15:13 ` David Laight [this message] 2020-07-28 15:13 ` [PATCH v1 0/4] [RFC] Implement Trampoline File Descriptor David Laight 2020-07-28 15:13 ` David Laight 2020-07-28 16:32 ` Madhavan T. Venkataraman 2020-07-28 16:32 ` Madhavan T. Venkataraman 2020-07-28 16:32 ` Madhavan T. Venkataraman 2020-07-28 17:16 ` Andy Lutomirski 2020-07-28 17:16 ` Andy Lutomirski 2020-07-28 17:16 ` Andy Lutomirski 2020-07-28 17:39 ` Madhavan T. Venkataraman 2020-07-29 5:16 ` Andy Lutomirski 2020-07-29 5:16 ` Andy Lutomirski 2020-07-29 5:16 ` Andy Lutomirski 2020-07-28 18:52 ` Madhavan T. Venkataraman 2020-07-28 18:52 ` Madhavan T. Venkataraman 2020-07-28 18:52 ` Madhavan T. Venkataraman 2020-07-29 8:36 ` David Laight 2020-07-29 8:36 ` David Laight 2020-07-29 8:36 ` David Laight 2020-07-29 17:55 ` Madhavan T. Venkataraman 2020-07-29 17:55 ` Madhavan T. Venkataraman 2020-07-29 17:55 ` Madhavan T. Venkataraman 2020-07-28 16:05 ` Casey Schaufler 2020-07-28 16:05 ` Casey Schaufler 2020-07-28 16:49 ` Madhavan T. Venkataraman 2020-07-28 16:49 ` Madhavan T. Venkataraman 2020-07-28 17:05 ` James Morris 2020-07-28 17:05 ` James Morris 2020-07-28 17:08 ` Madhavan T. Venkataraman 2020-07-28 17:08 ` Madhavan T. Venkataraman 2020-07-28 17:31 ` Andy Lutomirski 2020-07-28 17:31 ` Andy Lutomirski 2020-07-28 17:31 ` Andy Lutomirski 2020-07-28 19:01 ` Madhavan T. Venkataraman 2020-07-28 19:01 ` Madhavan T. Venkataraman 2020-07-29 13:29 ` Florian Weimer 2020-07-29 13:29 ` Florian Weimer 2020-07-29 13:29 ` Florian Weimer 2020-07-30 13:09 ` David Laight 2020-07-30 13:09 ` David Laight 2020-08-02 11:56 ` Pavel Machek 2020-08-02 11:56 ` Pavel Machek 2020-08-03 8:08 ` David Laight 2020-08-03 8:08 ` David Laight 2020-08-03 15:57 ` Madhavan T. Venkataraman 2020-08-03 15:57 ` Madhavan T. Venkataraman 2020-07-30 14:24 ` Madhavan T. Venkataraman 2020-07-30 20:54 ` Andy Lutomirski 2020-07-30 20:54 ` Andy Lutomirski 2020-07-30 20:54 ` Andy Lutomirski 2020-07-31 17:13 ` Madhavan T. Venkataraman 2020-07-31 17:13 ` Madhavan T. Venkataraman 2020-07-31 18:31 ` Mark Rutland 2020-07-31 18:31 ` Mark Rutland 2020-08-03 8:27 ` David Laight 2020-08-03 8:27 ` David Laight 2020-08-03 16:03 ` Madhavan T. Venkataraman 2020-08-03 16:03 ` Madhavan T. Venkataraman 2020-08-03 16:57 ` David Laight 2020-08-03 16:57 ` David Laight 2020-08-03 17:00 ` Madhavan T. Venkataraman 2020-08-03 17:00 ` Madhavan T. Venkataraman 2020-08-03 17:58 ` Madhavan T. Venkataraman 2020-08-03 17:58 ` Madhavan T. Venkataraman 2020-08-04 13:55 ` Mark Rutland 2020-08-04 13:55 ` Mark Rutland 2020-08-04 14:33 ` David Laight 2020-08-04 14:33 ` David Laight 2020-08-04 14:44 ` David Laight 2020-08-04 14:44 ` David Laight 2020-08-04 14:48 ` Madhavan T. Venkataraman 2020-08-04 14:48 ` Madhavan T. Venkataraman 2020-08-04 15:46 ` Madhavan T. Venkataraman 2020-08-04 15:46 ` Madhavan T. Venkataraman 2020-08-02 13:57 ` Florian Weimer 2020-08-02 13:57 ` Florian Weimer 2020-08-02 13:57 ` Florian Weimer 2020-07-30 14:42 ` Madhavan T. Venkataraman 2020-07-30 14:42 ` Madhavan T. Venkataraman 2020-08-02 18:54 ` Madhavan T. Venkataraman 2020-08-02 18:54 ` Madhavan T. Venkataraman 2020-08-02 20:00 ` Andy Lutomirski 2020-08-02 20:00 ` Andy Lutomirski 2020-08-02 20:00 ` Andy Lutomirski 2020-08-02 22:58 ` Madhavan T. Venkataraman 2020-08-02 22:58 ` Madhavan T. Venkataraman 2020-08-03 18:36 ` Madhavan T. Venkataraman 2020-08-03 18:36 ` Madhavan T. Venkataraman 2020-08-10 17:20 ` Madhavan T. Venkataraman 2020-08-10 17:34 ` Madhavan T. Venkataraman 2020-08-10 17:34 ` Madhavan T. Venkataraman 2020-08-11 21:12 ` Madhavan T. Venkataraman 2020-08-11 21:12 ` Madhavan T. Venkataraman 2020-08-03 8:23 ` David Laight 2020-08-03 8:23 ` David Laight 2020-08-03 15:59 ` Madhavan T. Venkataraman 2020-08-03 15:59 ` Madhavan T. Venkataraman 2020-07-31 18:09 ` Mark Rutland 2020-07-31 18:09 ` Mark Rutland 2020-07-31 20:08 ` Madhavan T. Venkataraman 2020-07-31 20:08 ` Madhavan T. Venkataraman 2020-08-03 16:57 ` Madhavan T. Venkataraman 2020-08-03 16:57 ` Madhavan T. Venkataraman 2020-08-04 14:30 ` Mark Rutland 2020-08-04 14:30 ` Mark Rutland 2020-08-06 17:26 ` Madhavan T. Venkataraman 2020-08-06 17:26 ` Madhavan T. Venkataraman 2020-08-08 22:17 ` Pavel Machek 2020-08-08 22:17 ` Pavel Machek 2020-08-11 12:41 ` Madhavan T. Venkataraman 2020-08-11 12:41 ` Madhavan T. Venkataraman 2020-08-11 13:08 ` Pavel Machek 2020-08-11 13:08 ` Pavel Machek 2020-08-11 15:54 ` Madhavan T. Venkataraman 2020-08-11 15:54 ` Madhavan T. Venkataraman 2020-08-12 10:06 ` Mark Rutland 2020-08-12 10:06 ` Mark Rutland 2020-08-12 18:47 ` Madhavan T. Venkataraman 2020-08-12 18:47 ` Madhavan T. Venkataraman 2020-08-19 18:53 ` Mickaël Salaün 2020-08-19 18:53 ` Mickaël Salaün 2020-09-01 15:42 ` Mark Rutland 2020-09-01 15:42 ` Mark Rutland
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