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

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Message-ID: <87zjpf4w0j.fsf@rustcorp.com.au>
Date:	Fri, 08 Nov 2013 10:14:44 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Axel Lin <axel.lin@...ics.com>, Ming Lei <tom.leiming@...il.com>
Cc:	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!

Axel Lin <axel.lin@...ics.com> writes:
> 2013/11/7 Ming Lei <tom.leiming@...il.com>:
>> Hi,
>>
>> On Thu, Nov 7, 2013 at 10:47 AM, Axel Lin <axel.lin@...ics.com> wrote:
>>>
>>> hi Ming,
>>> Seems CONFIG_PAGE_OFFSET is not configurabe in "make menuconfig".
>>> And I found CONFIG_PAGE_OFFSET=0xC0000000 for all below configs...
>>> $ make at91_dt_defconfig; grep  CONFIG_PAGE_OFFSET .config
>>> $ make ep93xx_defconfig; grep  CONFIG_PAGE_OFFSET .config
>>> $ make imx_v4_v5_defconfig; grep CONFIG_PAGE_OFFSET .config
>>> $ make mxs_defconfig; grep CONFIG_PAGE_OFFSET .config
>>> $ make omap2plus_defconfig; grep CONFIG_PAGE_OFFSET .config
>>> $ make s3c6400_defconfig; grep CONFIG_PAGE_OFFSET .config
>>> $ make at91x40_defconfig; grep CONFIG_PAGE_OFFSET .config
>>> ( at91x40_defconfig is also arm7tdmi )
>>
>> Firstly it can be configured via VMSPLIT_3GVMSPLIT_2G/VMSPLIT_1G.
>>
>> Secondly, configurable or not isn't the point, and maybe some uclinux
>> platforms do not use CONFIG_PAGE_OFFSET at all, but they should
>> set it as a reasonable value or at least be below than the start link
>> address of vmlinux.
>
> Hi Ming,
>
> I found in arch/arm/include/asm/memory.h:
> CONFIG_PAGE_OFFSET is not used if !CONFIG_MMU.
> So looks like setting CONFIG_PAGE_OFFSET to other value still won't work.

This seems like the simplest solution, but it may mean you still have
crap in /proc/kallsyms.

Does it work for you?

Thanks,
Rusty.


diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 32b10f53d0b4..c3bd3efec4cc 100644
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -82,7 +82,9 @@ kallsyms()
 		kallsymopt="${kallsymopt} --all-symbols"
 	fi
 
-	kallsymopt="${kallsymopt} --page-offset=$CONFIG_PAGE_OFFSET"
+	if [ -n "${CONFIG_MMU}" ]; then
+		kallsymopt="${kallsymopt} --page-offset=$CONFIG_PAGE_OFFSET"
+	fi
 
 	local aflags="${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL}               \
 		      ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS}"
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