linux-kernel - Re: kernel BUG at kernel/kallsyms.c:222!

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Date:	Mon, 11 Nov 2013 18:41:56 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Axel Lin <axel.lin@...ics.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Russell King <linux@....linux.org.uk>,
	Michal Marek <mmarek@...e.cz>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: kernel BUG at kernel/kallsyms.c:222!

Hi,

On Mon, Nov 11, 2013 at 5:57 PM, Ming Lei <tom.leiming@...il.com> wrote:
> Hi,
>
> On Mon, Nov 11, 2013 at 4:37 PM, Axel Lin <axel.lin@...ics.com> wrote:
>> 2013/11/11 Ming Lei <tom.leiming@...il.com>:
>>
>> Hi Ming,
>>
>> commit f6537f2f "scripts/kallsyms: filter symbols not in kernel address space",
>> uses CONFIG_PAGE_OFFSET as kernel_start_addr.
>> However, for !CONFIG_MMU case we have :
>>     PAGE_OFFSET != CONFIG_PAGE_OFFSET.
>
> Yes, it is the cause, and strictly speaking, commit f6537f2f is wrong,
> but triggered with bogus CONFIG_PAGE_OFFSET if !CONFIG_MMU.
>
> We can fix it either by Rusty's patch or removing the bogus
> CONFIG_PAGE_OFFSET for !CONFIG_MMU.

Rusty, maybe we need revert commit f6537f2f "scripts/kallsyms: filter
symbols not in kernel address space", since CONFIG_PAGE_OFFSET
may be bogus on !MMU or not defined on ARCHs(most of 64bit arch,
no regression report because scripts/kallsyms may get zero
kernel_start_addr)

As I thought of, another way for fixing original problem is to define a RO
global variable in kernel and set its value as PAGE_OFFSET, then let
scripts/kallsyms use it as kernel start address, or do you other
suggestions?


Thanks,
-- 
Ming Lei
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