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 08:27:25 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Mark Rutland' <>, "Madhavan T. Venkataraman"
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

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


Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

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.