Re: [RFC V2] mm: Generalize notify_page_fault()

Anshuman Khandual
2019-06-06T02:03:47Z

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.