linux-kernel - Re: [PATCH v2] ARM: Use udiv/sdiv for __aeabi

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 12 Nov 2013 10:20:10 -0500 (EST)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Måns Rullgård <mans@...sr.com>
cc:	Ben Dooks <ben.dooks@...ethink.co.uk>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Stephen Boyd <sboyd@...eaurora.org>,
	linux-kernel@...r.kernel.org,
	Christopher Covington <cov@...eaurora.org>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] ARM: Use udiv/sdiv for __aeabi_{u}idiv library
 functions

On Tue, 12 Nov 2013, Nicolas Pitre wrote:

> On Tue, 12 Nov 2013, Måns Rullgård wrote:
> 
> > It might be possible to extract this information from relocation tables.
> 
> True, but only for individual .o files.  Once the linker puts them 
> together the information is lost, and trying to infer what the linker 
> has done is insane.
> 
> Filtering the compiler output to annotate idiv calls before it is 
> assembled would probably be a better solution.

Another solution is to patch the call site from within __aeabi_idiv at 
run time using lr.  That wouldn't work in the presence of tail call 
optimization though.

Again this might not be worth it and patching __aeabi_idiv instead might 
be a good enough compromize.


Nicolas