> On Mar 2, 2021, at 12:25 PM, Oleg Nesterov <o...@redhat.com> wrote:
>
> On 03/01, Andy Lutomirski wrote:
>>
>>> On Mon, Mar 1, 2021 at 8:51 AM Oleg Nesterov <o...@redhat.com> wrote:
>>>
>>> But I guess this has nothing to do with uprobes, they do not single-step
>>> in kernel mode, right?
>>
>> They single-step user code, though, and the code that makes this work
>> is quite ugly. Single-stepping on x86 is a mess.
>
> But this doesn't really differ from, say, gdb doing si ? OK, except uprobes
> have to hook DIE_DEBUG. Nevermind...
Also, gdb doing so isn’t great either. Single stepping over a pushf
instruction, signal delivery, or a syscall on x86 is a mess.
>
>>>> Uprobes seem to single-step user code for no discernable reason.
>>>> (They want to trap after executing an out of line instruction, AFAICT.
>>>> Surely INT3 or even CALL after the out-of-line insn would work as well
>>>> or better.)
>>>
>>> Uprobes use single-step from the very beginning, probably because this
>>> is the most simple and "standard" way to implement xol.
>>>
>>> And please note that CALL/JMP/etc emulation was added much later to fix the
>>> problems with non-canonical addresses, and this emulation it still
>>> incomplete.
>>
>> Is there something like a uprobe test suite?
>
> Afaik, no.
>
>> How maintained /
>
> Add Srikar who sent the initial implementation. I can only say that I am glad
> that
> ./scripts/get_maintainer.pl no longer mentions me ;) I did some changes
> (including
> emulation) but a) this was a long ago and b) only because I was forced^W
> asked to
> fix the numerous bugs in this code.
>
>> actively used is uprobe?
>
> I have no idea, sorry ;)
>
> Oleg.
>
