From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com> To: David Laight <David.Laight@ACULAB.COM>, 'Mark Rutland' <mark.rutland@arm.com> Cc: Andy Lutomirski <luto@kernel.org>, Kernel Hardening <kernel-hardening@lists.openwall.com>, Linux API <linux-api@vger.kernel.org>, linux-arm-kernel <linux-arm-kernel@lists.infradead.org>, Linux FS Devel <linux-fsdevel@vger.kernel.org>, linux-integrity <linux-integrity@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>, LSM List <linux-security-module@vger.kernel.org>, Oleg Nesterov <oleg@redhat.com>, X86 ML <x86@kernel.org> Subject: Re: [PATCH v1 0/4] [RFC] Implement Trampoline File Descriptor Date: Mon, 3 Aug 2020 12:00:04 -0500 [thread overview] Message-ID: <b28abf39-8b62-f861-1325-aa7ce28fa6d3@linux.microsoft.com> (raw) In-Reply-To: <f87f84e466a041fbabd2bba84f4592a5@AcuMS.aculab.com> On 8/3/20 11:57 AM, David Laight wrote: > From: Madhavan T. Venkataraman >> Sent: 03 August 2020 17:03 >> >> On 8/3/20 3:27 AM, David Laight wrote: >>> From: Mark Rutland >>>> Sent: 31 July 2020 19:32 >>> ... >>>>> It requires PC-relative data references. I have not worked on all architectures. >>>>> So, I need to study this. But do all ISAs support PC-relative data references? >>>> Not all do, but pretty much any recent ISA will as it's a practical >>>> necessity for fast position-independent code. >>> i386 has neither PC-relative addressing nor moves from %pc. >>> The cpu architecture knows that the sequence: >>> call 1f >>> 1: pop %reg >>> is used to get the %pc value so is treated specially so that >>> it doesn't 'trash' the return stack. >>> >>> So PIC code isn't too bad, but you have to use the correct >>> sequence. >> Is that true only for 32-bit systems only? I thought RIP-relative addressing was >> introduced in 64-bit mode. Please confirm. > I said i386 not amd64 or x86-64. I am sorry. My bad. > > So yes, 64bit code has PC-relative addressing. > But I'm pretty sure it has no other way to get the PC itself > except using call - certainly nothing in the 'usual' instructions. OK. Madhavan
next prev parent reply other threads:[~2020-08-03 17:00 UTC|newest] 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 ` [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 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 [this message] 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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