linux-kernel - Re: [PATCH 2/3] ARM: kexec: copying code to ioremapped area

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Date:	Wed, 22 Jan 2014 21:03:54 +0800
From:	Wang Nan <wangnan0@...wei.com>
To:	Vaibhav Bedia <vaibhav.bedia@...il.com>
CC:	<kexec@...ts.infradead.org>, <stable@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Geng Hui <hui.geng@...wei.com>,
	<linux-mm@...ck.org>, Eric Biederman <ebiederm@...ssion.com>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux ARM Kernel List <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/3] ARM: kexec: copying code to ioremapped area

On 2014/1/22 20:56, Vaibhav Bedia wrote:
> On Wed, Jan 22, 2014 at 6:25 AM, Wang Nan <wangnan0@...wei.com <mailto:wangnan0@...wei.com>> wrote:
> 
>     ARM's kdump is actually corrupted (at least for omap4460), mainly because of
>     cache problem: flush_icache_range can't reliably ensure the copied data
>     correctly goes into RAM. After mmu turned off and jump to the trampoline, kexec
>     always failed due to random undef instructions.
> 
>     This patch use ioremap to make sure the destnation of all memcpy() is
>     uncachable memory, including copying of target kernel and trampoline.
> 
> 
> AFAIK ioremap on RAM in forbidden in ARM and device memory that ioremap()
> ends up creating is not meant for executable code.
> 
> Doesn't this trigger the WARN_ON() in _arm_ioremap_pfn_caller)?

This patch is depend on the previous one:

ARM: Premit ioremap() to map reserved pages

However, Russell is opposed to it.


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