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

From: Masami Hiramatsu <[email-masked]>
Date: Mon, 13 Sep 2010 16:15:58 +0900

(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 <[email-masked]> wrote:
>>> From: Randy Dunlap <[email-masked]>
>>>
>>> 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 <[email-masked]>
>>> Cc:     Ananth N Mavinakayanahalli <[email-masked]>
>>> Cc:     Anil S Keshavamurthy <[email-masked]>
>>> Cc:     "David S. Miller" <[email-masked]>
>>> Cc:     Masami Hiramatsu <[email-masked]>
>>> ---
>>>  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 <[email-masked]>
>>
> 
> 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.

Thank you,

-- 
Masami HIRAMATSU
2nd Dept. Linux Technology Center
Hitachi, Ltd., Systems Development Laboratory
E-mail: [email-masked]