Sorry I forgot to reply to the list. :( It's my first time doing this.
On 4/14/25 4:56 PM, Dave Hansen wrote:
> On 4/14/25 13:52, Junxuan Liao wrote:
>> On 4/14/25 3:42 PM, Dave Hansen wrote:
>>> Is there a reason kprobes don't work for this?
>>
>> In this code path it's either noinstr or inline functions, so I believe
>> explicit tracepoints are necessary?
>
> It'd be great to turn this "??" into some more certainty. ;)
>
>> As Steven has mentioned, there are similar tracepoints for irq and it's
>> nice to have them for page faults too.
>
> So, that code is:
>
>> trace_irq_handler_entry(irq, action);
>> res = action->handler(irq, action->dev_id);
>> trace_irq_handler_exit(irq, action, res);
>
> ... I think.
>
> That's a heck of a lot simpler than a couple static keys and new
> conditionals.
>
> Also, I honestly don't think we need separate user and kernel fault
> trace points. Maybe we should just zap that in the process.
>
> Is there a reason we couldn't get this down to something dirt simple like:
>
> DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
> {
> instrumentation_begin();
> + trace_page_fault_entry(...);
> handle_page_fault(regs, error_code, address);
> + trace_page_fault_exit(...);
> instrumentation_end();
>
> ??
If we don't need to separate user and kernel tracepoints, we won't need
those static keys anyway, and it's indeed much simpler.
Do people find separate user/kernel tracepoints useful? For me, I can
check regs in eBPF tracing code instead.
Junxuan
