Re: [PATCH] scripts/kallsyms: filter symbols not in kernel address space

From: Ming Lei
Date: Tue Jan 07 2014 - 09:33:48 EST

Hi Arnd,

On Tue, Jan 7, 2014 at 10:12 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> On Monday 28 October 2013, Ming Lei wrote:
>> This patch uses CONFIG_PAGE_OFFSET to filter symbols which
>> are not in kernel address space because these symbols are
>> generally for generating code purpose and can't be run at
>> kernel mode, so we needn't keep them in /proc/kallsyms.
>> For example, on ARM there are some symbols which are
>> linked in relocatable code section, then perf can't parse
>> symbols any more from /proc/kallsyms, and this patch fixes
>> the problem.
>> Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
>> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
>> Cc: Michal Marek <mmarek@xxxxxxx>
>> Acked-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
>> Signed-off-by: Ming Lei <tom.leiming@xxxxxxxxx>
> Sorry for the late report, but I seem to have encountered a problem with this
> patch, now that it has made it into all stable kernels.
> When linking an ARM nommu kernel, I get the output "No valid symbol." twice,
> from scripts/kallsyms. The problem evidently is that PAGE_OFFSET is still
> set to 0xC0000000 on ARM NOMMU builds but the kernel is linked to start at
> PLAT_PHYS_OFFSET instead, which may be elsehwere. For most platforms,
> this is defined in Kconfig these days, so we could get away with
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index d1e4098..c477a7c 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -1592,6 +1592,7 @@ endchoice
> config PAGE_OFFSET
> hex
> + default PHYS_OFFSET if !MMU
> default 0x40000000 if VMSPLIT_1G
> default 0x80000000 if VMSPLIT_2G
> default 0xC0000000
> but there are still a few ARM platforms that define their own PLAT_PHYS_OFFSET
> in memory.h, and it wouldn't help on non-ARM systems that might have the same
> problem.

We had posted two patches to address the problem, see below link:

Ming Lei
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