linux-kernel - Re: [PATCH] ARM: decompressor: remove unused cache flush code

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: <20150122154400.GB26493@n2100.arm.linux.org.uk>
Date:	Thu, 22 Jan 2015 15:44:00 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Cc:	Masahiro Yamada <yamada.m@...panasonic.com>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Heiko Stuebner <heiko@...ech.de>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Will Deacon <will.deacon@....com>,
	linux-kernel@...r.kernel.org,
	Ben Dooks <ben.dooks@...ethink.co.uk>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: decompressor: remove unused cache flush code

On Thu, Jan 22, 2015 at 09:06:47AM +0100, Uwe Kleine-König wrote:
> Hello,
> 
> On Thu, Jan 22, 2015 at 02:22:58PM +0900, Masahiro Yamada wrote:
> > As ARM ARM says, the bit 19-16 of ID_MMFR1 is always 0b0000 because
> > ARMv7 requires a hierarchical cache implementation.
> > The line "mcr    p15, 0, r10, c7, c14, 0" is not reachable.
> > 
> > Moreover, the v7_flush_dcache_all in arch/arm/mm/cache-v7.S does not
> > check the ID_MMFR1.
> > 
> > Signed-off-by: Masahiro Yamada <yamada.m@...panasonic.com>
> I stumbled about this some time ago, too. The thing is however that the
> __armv7_mmu_cache functions are selected if
> CPUID & 0x000f0000 == 0x000f0000, and that is (AFAIK at present only
> theoretically) not implying that we have an ARMv7 machine. Only that it
> uses the "CPUID Identification Scheme" which is required on ARMv7.

Correct, and there are ARMv6 CPUs which satisfy the "CPUID identification
scheme" test - and are probably not heirarchial.

-- 
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/