Date:	Tue, 04 Feb 2014 22:29:20 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Chen Gang <gang.chen.5i5j@...il.com>
Cc:	ananth@...ibm.com, anil.s.keshavamurthy@...el.com,
	Håvard Skinnemoen 
	<hskinnemoen@...il.com>, David Miller <davem@...emloft.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Hans-Christian Egtvedt <egtvedt@...fundet.no>,
	"yrl.pp-manager.tt@...achi.com" <yrl.pp-manager.tt@...achi.com>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] kernel: kprobe: move all *kretprobe* generic implementation
 to CONFIG_KRETPROBES enabled area

(2014/02/04 21:07), Chen Gang wrote:
> On 02/04/2014 03:17 PM, Masami Hiramatsu wrote:
>> (2014/02/04 14:16), Chen Gang wrote:
>>> When CONFIG_KRETPROBES disabled, all *kretprobe* generic implementation
>>> are useless, so need move them to CONFIG_KPROBES enabled area.
>>>
>>> Now, *kretprobe* generic implementation are all implemented in 2 files:
>>>
>>>  - in "include/linux/kprobes.h":
>>>
>>>      move inline kretprobe*() to CONFIG_KPROBES area and dummy outside.
>>>      move some *kprobe() declarations which kretprobe*() call, to front.
>>>      not touch kretprobe_blacklist[] which is architecture's variable.
>>>
>>>  - in "kernel/kprobes.c":
>>>
>>>      move all kretprobe* to CONFIG_KPROBES area and dummy outside.
>>>      define kretprobe_flush_task() to let kprobe_flush_task() call.
>>>      define init_kretprobes() to let init_kprobes() call.
>>>
>>> The patch passes compiling (get "kernel/kprobes.o" and "kernel/built-
>>> in.o") under avr32 and x86_64 allmodconfig, and passes building (get
>>> bzImage and Modpost modules) under x86_64 defconfig.
>>
>> Thanks for the fix! and I have some comments below.
>>
>>> Signed-off-by: Chen Gang <gang.chen.5i5j@...il.com>
>>> ---
>>>  include/linux/kprobes.h |  58 +++++----
>>>  kernel/kprobes.c        | 328 +++++++++++++++++++++++++++---------------------
>>>  2 files changed, 222 insertions(+), 164 deletions(-)
>>>
>>> diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
>>> index 925eaf2..c0d1212 100644
>>> --- a/include/linux/kprobes.h
>>> +++ b/include/linux/kprobes.h
>>> @@ -223,10 +223,36 @@ static inline int kprobes_built_in(void)
>>>   return 1;
>>>  }
>>>  
>>> +int disable_kprobe(struct kprobe *kp);
>>> +int enable_kprobe(struct kprobe *kp);
>>> +
>>> +void dump_kprobe(struct kprobe *kp);
>>> +
>>> +extern struct kretprobe_blackpoint kretprobe_blacklist[];
>>> +
>>>  #ifdef CONFIG_KRETPROBES
>>>  extern void arch_prepare_kretprobe(struct kretprobe_instance *ri,
>>>     struct pt_regs *regs);
>>>  extern int arch_trampoline_kprobe(struct kprobe *p);
>>> +static inline void kretprobe_assert(struct kretprobe_instance *ri,
>>> + unsigned long orig_ret_address, unsigned long trampoline_address)
>>> +{
>>> + if (!orig_ret_address || (orig_ret_address == trampoline_address)) {
>>> + printk(KERN_ERR
>>> + "kretprobe BUG!: Processing kretprobe %p @ %p\n",
>>> + ri->rp, ri->rp->kp.addr);
>>> + BUG();
>>> + }
>>> +}
>>> +static inline int disable_kretprobe(struct kretprobe *rp)
>>> +{
>>> + return disable_kprobe(&rp->kp);
>>> +}
>>> +static inline int enable_kretprobe(struct kretprobe *rp)
>>> +{
>>> + return enable_kprobe(&rp->kp);
>>> +}
>>> +
>>>  #else /* CONFIG_KRETPROBES */
>>>  static inline void arch_prepare_kretprobe(struct kretprobe *rp,
>>>   struct pt_regs *regs)
>>> @@ -236,19 +262,20 @@ static inline int arch_trampoline_kprobe(struct kprobe *p)
>>>  {
>>>   return 0;
>>>  }
>>> -#endif /* CONFIG_KRETPROBES */
>>> -
>>> -extern struct kretprobe_blackpoint kretprobe_blacklist[];
>>> -
>>>  static inline void kretprobe_assert(struct kretprobe_instance *ri,
>>>   unsigned long orig_ret_address, unsigned long trampoline_address)
>>>  {
>>> - if (!orig_ret_address || (orig_ret_address == trampoline_address)) {
>>> - printk("kretprobe BUG!: Processing kretprobe %p @ %p\n",
>>> - ri->rp, ri->rp->kp.addr);
>>> - BUG();
>>> - }
>>>  }
>>> +static inline int disable_kretprobe(struct kretprobe *rp)
>>> +{
>>> + return 0;
>>> +}
>>> +static inline int enable_kretprobe(struct kretprobe *rp)
>>> +{
>>> + return 0;
>>> +}
>>
>> No, these should returns -EINVAL or -ENOSYS, since these are user API.
> 
> OK, thanks, it sounds reasonable to me.
> 
>> Anyway, I don't think those inlined functions to be changed, because
>> most of them are internal functions. If CONFIG_KRETPROBES=n, it just
>> be ignored.
>>
> 
> In original implementation, if CONFIG_KRETPROBES=n, kretprobe_assert(),
> disable_kretprobe(), and enable_kretprobe() are not ignored.

Really? where are they called? I mean, those functions do not have
any instance unless your module uses it (but that is not what the kernel
itself should help).

> 
>> So, I think you don't need to change kprobes.h.
>>
> 
> So "kprobes.h" still need be changed.

Is there any concrete problem you have?

> 
>>> +
>>> +#endif /* CONFIG_KRETPROBES */
>>>  
>>>  #ifdef CONFIG_KPROBES_SANITY_TEST
>>>  extern int init_test_probes(void);
>>> @@ -379,11 +406,6 @@ void unregister_kretprobes(struct kretprobe **rps, int num);
>>>  void kprobe_flush_task(struct task_struct *tk);
>>>  void recycle_rp_inst(struct kretprobe_instance *ri, struct hlist_head *head);
>>>  
>>> -int disable_kprobe(struct kprobe *kp);
>>> -int enable_kprobe(struct kprobe *kp);
>>> -
>>> -void dump_kprobe(struct kprobe *kp);
>>> -
>>>  #else /* !CONFIG_KPROBES: */
>>>  
>>>  static inline int kprobes_built_in(void)
>>> @@ -459,14 +481,6 @@ static inline int enable_kprobe(struct kprobe *kp)
>>>   return -ENOSYS;
>>>  }
>>>  #endif /* CONFIG_KPROBES */
>>> -static inline int disable_kretprobe(struct kretprobe *rp)
>>> -{
>>> - return disable_kprobe(&rp->kp);
>>> -}
>>> -static inline int enable_kretprobe(struct kretprobe *rp)
>>> -{
>>> - return enable_kprobe(&rp->kp);
>>> -}
>>>  static inline int disable_jprobe(struct jprobe *jp)
>>>  {
>>>   return disable_kprobe(&jp->kp);
>>> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
>>> index ceeadfc..e305a81 100644
>>> --- a/kernel/kprobes.c
>>> +++ b/kernel/kprobes.c
>> [...]
>>> @@ -1936,8 +1955,44 @@ static int __kprobes pre_handler_kretprobe(struct kprobe *p,
>>>   return 0;
>>>  }
>>>  
>>> +void __kprobes recycle_rp_inst(struct kretprobe_instance *ri,
>>> + struct hlist_head *head)
>>> +{
>>> +}
>>> +
>>> +void __kprobes kretprobe_hash_lock(struct task_struct *tsk,
>>> + struct hlist_head **head, unsigned long *flags)
>>> +__acquires(hlist_lock)
>>> +{
>>> +}
>>> +
>>> +void __kprobes kretprobe_hash_unlock(struct task_struct *tsk,
>>> + unsigned long *flags)
>>> +__releases(hlist_lock)
>>> +{
>>> +}
>>> +
>>
>>> +static void __kprobes kretprobe_flush_task(struct task_struct *tk)
>>> +{
>>> +}
>>> +
>>> +static void __init init_kretprobes(void)
>>> +{
>>> +}
>>
>> These should be macros, as I did for optprobe functions
>> with !CONFIG_OPTPROBES.
>>
> 
> OK, thanks, it sounds reasonable to me.
> 
>  - For new added static functions: kretprobe_flush_task(), and
>    init_kretprobes() need be changed to macros
> 
>  - For extern functions: recycle_rp_inst(), kretprobe_hash_lock(), and
>    kretprobe_has_unlock(), need use dummy functions.
> 
>  - For original static function: pre_handler_kretprobe(), need still
>    use dummy function (for function pointer comparing).

Right :)

Thanks!

> 
> 
>> Other parts looks good to me!;)
>>
>> Thank you!
>>
>>
> 
> Thanks.
> 


-- 
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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