linux-kernel - Re: [PATCH v8 01/16] scripts: link-vmlinux: Don't pass page offset to kallsyms if XIP Kernel

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Message-ID: <555D12F8.4000403@suse.de>
Date:	Thu, 21 May 2015 01:04:24 +0200
From:	Andreas Färber <afaerber@...e.de>
To:	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Michal Marek <mmarek@...e.cz>, Stefan Agner <stefan@...er.ch>
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	Daniel Lezcano <daniel.lezcano@...aro.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Will Deacon <will.deacon@....com>,
	Nikolay Borisov <Nikolay.Borisov@....com>,
	Peter Meerwald <pmeerw@...erw.net>,
	"linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
	Jiri Slaby <jslaby@...e.cz>,
	Linux-Arch <linux-arch@...r.kernel.org>,
	Daniel Thompson <daniel.thompson@...aro.org>,
	Russell King <linux@....linux.org.uk>,
	Jonathan Corbet <corbet@....net>,
	Lee Jones <lee.jones@...aro.org>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Chanwoo Choi <cw00.choi@...sung.com>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	Antti Palosaari <crope@....fi>,
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	Uwe Kleine-König 
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	Rusty Russell <rusty@...tcorp.com.au>,
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	Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>
Subject: Re: [PATCH v8 01/16] scripts: link-vmlinux: Don't pass page offset
 to kallsyms if XIP Kernel

Hi,

Am 18.05.2015 um 13:47 schrieb Maxime Coquelin:
> 2015-05-09 9:53 GMT+02:00 Maxime Coquelin <mcoquelin.stm32@...il.com>:
>> When Kernel is executed in place from ROM, the symbol addresses can be
>> lower than the page offset.
>>
>> Tested-by: Chanwoo Choi <cw00.choi@...sung.com>
>> Signed-off-by: Maxime Coquelin <mcoquelin.stm32@...il.com>

This issue was reported by Stefan Agner in 2014 for the VF610 [1], not
sure if I asked already whether there should be a Reported-by line?
Stefan, have you had a chance to test this patch?

Back then on STM32F4 I debugged that disabling KALLSYMS works around it.

Now on a different XIP target I have confirmed this patch to help show a
stacktrace (my clk driver was missing some CLK_DIVIDER_ALLOW_ZEROs) ...
although my earlyprintk serial output still gets stuck further down the
stacktrace - probably unrelated.

[    0.000000] ------------[ cut here ]------------
[    0.000000] WARNING: CPU: 0 PID: 0 at drivers/clk/clk-divider.c:126
divider_recalc_rate+0x2b/0x44()
[    0.000000] SYS: Zero divisor and CLK_DIVIDER_ALLOW_ZERO not set
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted
4.1.0-rc4-next-20150519+ #23
[    0.000000] Hardware name: XMC4000 (Device Tree Support)
[    0.000000] [<0800bd5d>] (unwind_backtrace) from [<0800b0cb>]
(show_stack+0xb/0xc)
[    0.000000] [<0800b0cb>] (show_stack) from [<0800e0a5>]
(warn_slowpath_common+0x55/0x78)
[    0.000000] [<0800e0a5>] (warn_slowpath_common) from [<0800e103>]
(warn_slowpath_fmt+0x1b/0x24)
[    0.000000] [<0800e103>] (warn_slowpath_fmt) from [<080942e3>] (divide

But this is definitely an improvement for ARMv7-M debugging,

Tested-by: Andreas Färber <afaerber@...e.de>

> [Hi Michal, ...] could you consider
> taking it for v4.2?

Regards,
Andreas

[1]
http://lists.infradead.org/pipermail/linux-arm-kernel/2014-November/307297.html

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