linux-kernel - Re: [PATCH v2 2/2] ARM: at91: pm: switch to the PIE infrastructure

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] [day] [month] [year] [list]

Message-ID: <1503370.EB259eFnzi@ws-stein>
Date:	Wed, 29 Jun 2016 10:30:55 +0200
From:	Alexander Stein <alexander.stein@...tec-electronic.com>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Cc:	linux-kernel@...r.kernel.org,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org,
	Dave Martin <Dave.Martin@....com>,
	Doug Anderson <dianders@...omium.org>,
	Heiko Stuebner <heiko@...ech.de>,
	Nicolas Ferre <nicolas.ferre@...el.com>
Subject: Re: [PATCH v2 2/2] ARM: at91: pm: switch to the PIE infrastructure

On Wednesday 29 June 2016 09:57:14, Alexandre Belloni wrote:
> On 29/06/2016 at 08:12:21 +0200, Alexander Stein wrote :
> > > +#if defined(CONFIG_CPU_V7)
> > > +	dsb();
> > > +	wfi();
> > > +#else
> > > +	asm volatile ("mcr	p15, 0, %0, c7, c0, 4" \
> > > +		      : : "r" (0) : "memory");
> > > +#endif
> > 
> > Why not defining wfi() for __LINUX_ARM_ARCH__ < 7 as it is done for dsb()
> > and friends in arch/arm/include/asm/barrier.h? So you can get rid of that
> > #if completly.
> 
> Well, Russell said it was not useful because "there's no architected WFI
> instruction which doesn't have CPU specific issues (hence why we have
> cpu_do_idle() to abstract that)"

Wouldn't you suffer from this here as well? Anyway, the inline assembly above 
is what is actually wfi but using CP15. I checked several proc-*.S in do_idle 
and they all have
> "mcr     p15, 0, r0, c7, c0, 4           @ Wait for interrupt"
at some point. so this inline assembly could actually be implemented on wfi() 
macro.

Best regards,
Alexander