Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Mon, 3 Aug 2020 11:03:21 -0500
From: "Madhavan T. Venkataraman" <>
To: David Laight <David.Laight@...LAB.COM>,
 'Mark Rutland' <>
Cc: Andy Lutomirski <>,
 Kernel Hardening <>,
 Linux API <>,
 linux-arm-kernel <>,
 Linux FS Devel <>,
 linux-integrity <>,
 LKML <>,
 LSM List <>,
 Oleg Nesterov <>, X86 ML <>
Subject: Re: [PATCH v1 0/4] [RFC] Implement Trampoline File Descriptor

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.


Powered by blists - more mailing lists

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.