Re: [bug report][stable] perf probe: failed to add events

Joseph Qi
2019-02-26T12:32:43Z

On 19/2/26 17:05, Greg KH wrote:
> On Tue, Feb 26, 2019 at 03:31:14PM +0800, Joseph Qi wrote:
>> Hi,
>>
>> I'm using kernel v4.19.24 and have found that there is an issue when
>> using perf probe to define a new dynamic tracepoint.
>>
>> $ perf probe -a handle_mm_fault
>> Failed to write event: Numerical result out of range
>> Error: Failed to add events.
>>
>> I've also tried kernel v4.20, and it can pass.
>
> Ick, has this ever worked on the 4.19 stable tree? If so, any chance
> you can run 'git bisect' to find the offending commit?
>
From my test, v4.19.0 also has this issue.
Bisect locates that it is introduced by commit bf904d2762ee
"x86/pti/64: Remove the SYSCALL64 entry trampoline".

Thanks,
Joseph

>> So I've bisected and finally found the first good commit is:
>> bf904d2762ee x86/pti/64: Remove the SYSCALL64 entry trampoline
>> which is based on another commit:
>> 98f05b5138f0 Use the TSS sp2 slot for SYSCALL/SYSRET scratch space
>>
>> Once I've backpoted these two commits into 4.19.24, the above case can
>> pass, though I'm not sure how it is fixed.
>> So is there any plan to let them go into stable as well?
>
> If they are needed, I'll gladly queue them up, but this feels like
> something might have broken, so it should be easier to just revert the
> offending commit instead.
>
> Andy, any ideas?
>
> thanks,
>
> greg k-h
>