[RFC V2] mm: Generalize notify_page_fault()

[Anshuman Khandual]

On 06/05/2019 03:23 AM, Matthew Wilcox wrote:
> On Tue, Jun 04, 2019 at 12:04:06PM +0530, Anshuman Khandual wrote:
>> +++ b/arch/x86/mm/fault.c
>> @@ -46,23 +46,6 @@ kmmio_fault(struct pt_regs *regs, unsigned long addr)
>>  	return 0;
>>  }
>>  
>> -static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
>> -{
> ...
>> -}
> 
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index 0e8834a..c5a8dcf 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -1778,6 +1778,7 @@ static inline int pte_devmap(pte_t pte)
>>  }
>>  #endif
>>  
>> +int notify_page_fault(struct pt_regs *regs, unsigned int trap);
> 
> Why is it now out-of-line?  

Did not get it. AFAICS it is the same from last version and does not cross
80 characters limit on that line.

> 
>> +++ b/mm/memory.c
>> +int __kprobes notify_page_fault(struct pt_regs *regs, unsigned int trap)
>> +{
>> +	int ret = 0;
>> +
>> +	/*
>> +	 * To be potentially processing a kprobe fault and to be allowed
>> +	 * to call kprobe_running(), we have to be non-preemptible.
>> +	 */
>> +	if (kprobes_built_in() && !preemptible() && !user_mode(regs)) {
>> +		if (kprobe_running() && kprobe_fault_handler(regs, trap))
>> +			ret = 1;
>> +	}
>> +	return ret;
>> +}
>> +
> 
> I would argue this should be in kprobes.h as a static nokprobe_inline.

We can do that. Though it will be a stand alone (not inside #ifdef) as it
already takes care of CONFIG_KPROBES via kprobes_built_in(). Will change
it and in which case the above declaration in mm.h would not be required.