linux-kernel - Re: [PATCH -next] optprobes: fix kconfig depends/selects

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Message-ID: <AANLkTimF6GK1hC2e5oSQ7Me9nrBOnS1q7f2rVORC1pUD@mail.gmail.com>
Date:	Mon, 13 Sep 2010 14:11:45 +0300
From:	Felipe Contreras <felipe.contreras@...il.com>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Randy Dunlap <randy.dunlap@...cle.com>,
	lkml <linux-kernel@...r.kernel.org>, linux-next@...r.kernel.org,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	akpm <akpm@...ux-foundation.org>,
	2nddept-manager@....hitachi.co.jp
Subject: Re: [PATCH -next] optprobes: fix kconfig depends/selects

On Mon, Sep 13, 2010 at 1:14 PM, Masami Hiramatsu
<masami.hiramatsu.pt@...achi.com> wrote:
> (2010/09/13 18:41), Felipe Contreras wrote:
>> On Mon, Sep 13, 2010 at 10:15 AM, Masami Hiramatsu
>> <masami.hiramatsu.pt@...achi.com> wrote:
>>> (2010/09/13 10:06), Masami Hiramatsu wrote:
>>>> (2010/09/12 19:49), Felipe Contreras wrote:
>>>>> On Thu, Aug 12, 2010 at 10:26 PM, Randy Dunlap <randy.dunlap@...cle.com> wrote:
>>>>>> From: Randy Dunlap <randy.dunlap@...cle.com>
>>>>>>
>>>>>> KALLSYMS and KALLSYMS_ALL depend on DEBUG_KERNEL, so add that dependency.
>>>>>> KALLSYMS_ALL depends on KALLSYMS, so select both of them, not just KALLSYMS_ALL.
>>>>>>
>>>>>> warning: (OPTPROBES && KPROBES && HAVE_OPTPROBES && !PREEMPT || MTD_UBI_DEBUG && MTD && SYSFS && MTD_UBI || UBIFS_FS_DEBUG && MISC_FILESYSTEMS && UBIFS_FS || LOCKDEP && DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT || LATENCYTOP && HAVE_LATENCYTOP_SUPPORT) selects KALLSYMS_ALL which has unmet direct dependencies (DEBUG_KERNEL && KALLSYMS)
>>>>>>
>>>>>> Signed-off-by: Randy Dunlap <randy.dunlap@...cle.com>
>>>>>> Cc:     Ananth N Mavinakayanahalli <ananth@...ibm.com>
>>>>>> Cc:     Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
>>>>>> Cc:     "David S. Miller" <davem@...emloft.net>
>>>>>> Cc:     Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
>>>>>> ---
>>>>>>  arch/Kconfig |    2 ++
>>>>>>  1 file changed, 2 insertions(+)
>>>>>>
>>>>>> --- linux-next-20100810.orig/arch/Kconfig
>>>>>> +++ linux-next-20100810/arch/Kconfig
>>>>>> @@ -45,6 +45,8 @@ config OPTPROBES
>>>>>>        def_bool y
>>>>>>        depends on KPROBES && HAVE_OPTPROBES
>>>>>>        depends on !PREEMPT
>>>>>> +       depends on DEBUG_KERNEL
>>>>>> +       select KALLSYMS
>>>>>>        select KALLSYMS_ALL
>>>>>>
>>>>>>  config HAVE_EFFICIENT_UNALIGNED_ACCESS
>>>>>> --
>>>>>
>>>>> This causes another problem:
>>>>>
>>>>> arch/Kconfig:33:error: recursive dependency detected!
>>>>> arch/Kconfig:33:     symbol KPROBES depends on KALLSYMS
>>>>> init/Kconfig:825:    symbol KALLSYMS is selected by OPTPROBES
>>>>> arch/Kconfig:44:     symbol OPTPROBES depends on KPROBES
>>>>>
>>>>> The 'select KALLSYMS' is redundant.
>>>>>
>>>>> Otherwise: Signed-off-by: Felipe Contreras <felipe.contreras@...il.com>
>>>>>
>>>>
>>>> Thanks, let me clear the dependency;
>>>> Kprobes uses kallsyms_lookup for finding target function and checking
>>>> instruction boundary, thus CONFIG_KPROBES should select CONFIG_KALLSYMS
>>>> and CONFIG_KALLSYMS_ALL.
>>>> Optprobe is a optional feature which is supported on x86 arch, and
>>>> it also uses kallsyms_lookup for checking instructions in the target
>>>> function. Anyway, since optprobe itself is depends on kprobes, it doesn't
>>>> need to select both of KALLSYMS/KALLSYMS_ALL.
>>>
>>> Hmm, wait, I might misunderstand something here. I thought
>>> KALLSYMS_ALL added symbols of static functions.
>>> But, does KALLSYMS_ALL just add symbols of variables?
>>> If so, both of KPROBES and OPTPROBES require only KALLSYMS.
>>> It means that they don't need to care about CONFIG_DEBUG_KERNEL.
>>
>> So:
>> -       select KALLSYMS_ALL
>> +       depends on KALLSYMS_ALL
>>
>> Because KALLSYMS_ALL depends on DEBUG_KERNEL && KALLSYMS.
>
> No, what I meant is;
> -       select KALLSYMS_ALL
>
> :-)

Ohh, I didn't notice the _ALL. Makes sense.

-- 
Felipe Contreras
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