[lldb-dev] JIT debugging and Windows

Fri Jan 3 14:35:02 PST 2014

Everything I've been doing with that was upstream llvm to get the
relocations right rather than lldb.
https://github.com/loladiro/lldb/commit/991583df4d052cb7dab692e657c4ced4d01ff384is
up to date (the next commit on master has a few debugging things I was
trying out, but that commit is functionally complete).

Yes, I thought about that solution as well. Seems like the way to go.

On Thu, Jan 2, 2014 at 11:56 AM, Andrew MacPherson <andrew.macp at gmail.com>wrote:

> Hi Keno,
>
> This all sounds great, can you check in the progress you've made so far
> with seeing JITed functions in backtraces? I can try to figure out what's
> happening with the missing line numbers.
>
> Regarding the breakpoints a quick look at Breakpoint.cpp seems to show
> that this is intentional, there's an explicit check for !IsInternal()
> inside Breakpoint::ModulesChanged() which I would guess is what applies
> here. I think we would want these breakpoints to be internal though so that
> users don't see them and if we make sure that the JITLoader gets an event
> whenever a new shared library is loaded then we can also add more explicit
> logging around when the JIT register code function has actually been found
> and resolved.
>
> Thanks!
> Andrew
>
>
> On Wed, Jan 1, 2014 at 3:39 PM, Keno Fischer <kfischer at college.harvard.edu
> > wrote:
>
>> I'm currently in holiday mode as well. A couple of things that I didn't
>> get to that need to be resolved (these are pretty general questions on lldb
>> itself, so I'd appreciate input from anybody on this list):
>>
>> - I'm using a regular rather than an internal breakpoint, because the
>> latter does not get updated when shared libraries are loaded (Is this
>> intended? Is there a recommended workaround?)
>>
>> - I'm not seeing the function in backtraces even though I can set
>> breakpoints. Is there anything else that needs to be done/ Do the
>> backtraces use different information that is perhaps not relocated
>> properly? If so, how can I check?
>>
>> - I'm also not seeing line numbers, etc. Probably related to the second
>> point.
>>
>> - Keno
>>
>>
>> On Tue, Dec 31, 2013 at 10:16 AM, Andrew MacPherson <
>> andrew.macp at gmail.com> wrote:
>>
>>> This looks great. I'm still in holiday mode but will tackle any
>>> outstanding ELF-related work when I'm back on Thursday, feel free to ping
>>> me or the list again if you get any further. Thanks for pushing on this!
>>>
>>> Cheers,
>>> Andrew
>>>
>>>
>>> On Sun, Dec 29, 2013 at 6:29 PM, Keno Fischer <
>>> kfischer at college.harvard.edu> wrote:
>>>
>>>> I've gotten pretty far,
>>>> Code is here: https://github.com/loladiro/lldb
>>>> It's interacting correctly with the debug interface and I've got it
>>>> loading the object file from memory correctly for
>>>> MachO/DWARF (working on ELF right now). Currently not much use as it
>>>> doesn't seem to be looking at the
>>>> debug information that were just added (I can see them via `image dump
>>>> sections` and I can set breakpoints
>>>> correctly though, so that's a plus). For DWARF, there's a few changes
>>>> for upstream LLVM needed. I'll put them
>>>> up if anybody's interested, otherwise, I'll just keep chugging along
>>>> and wait until I have more complete patch.
>>>>
>>>> - Keno
>>>>
>>>>
>>>> On Sat, Dec 28, 2013 at 1:07 PM, Andrew MacPherson <
>>>> andrew.macp at gmail.com> wrote:
>>>>
>>>>> Hi Keno,
>>>>>
>>>>> I noticed the same thing and agree that the JIT loader doesn't
>>>>> perfectly fit as a DynamicLoader, the suggestion from a couple of years
>>>>> back on the list was to make the Process -> DynamicLoader relationship 1:n
>>>>> but I prefer your suggestion of adding a new plugin type (JITLoader). Right
>>>>> now there would only be one JITLoader type for the GDB interface.
>>>>>
>>>>> The patch could probably be fixed up as-is as a first step (leaving
>>>>> the JIT loading bits as a growth on the DynamicLoaderPOSIXDYLD) and we
>>>>> could move it out into its own plugin type once that's working. I should
>>>>> have time this coming week to get this working but if you'll also have time
>>>>> then I'm happy to leave it with you.
>>>>>
>>>>> Cheers,
>>>>> Andrew
>>>>>
>>>>>
>>>>> On Sat, Dec 28, 2013 at 9:37 AM, Keno Fischer <
>>>>> kfischer at college.harvard.edu> wrote:
>>>>>
>>>>>> I've started looking into this and it's actually not that difficult
>>>>>> to do (the JIT part at least). I think the most difficult thing is
>>>>>> figuring out where to put the functionality. The way I see it, the
>>>>>> JIT interface is almost a DynamicLoader, with the difference
>>>>>> that asking it about things like whether or not loading a dynamic
>>>>>> library is safe doesn't make much sense. Another problem
>>>>>> is that currently there's a 1:1 relationship between Processes and
>>>>>> DynamicLoaders. Perhaps a new class of Plugins
>>>>>> (JITLoader?) could be added with a 1:n relationship to processes.
>>>>>> Some of the interface (I'm thinking
>>>>>>  DidLaunch,DidAttach,Get/SetStopWhenImagesChange) could be pulled out
>>>>>> into an abstract base class. Does that make
>>>>>> sense. I'd be happy to implement this once we decide on the design.
>>>>>>
>>>>>> Keno
>>>>>>
>>>>>>
>>>>>> On Wed, Dec 25, 2013 at 10:30 AM, Andrew MacPherson <
>>>>>> andrew.macp at gmail.com> wrote:
>>>>>>
>>>>>>> Looks great, thanks Keno. I'll look into this next week and keep you
>>>>>>> posted.
>>>>>>>
>>>>>>> Cheers,
>>>>>>> Andrew
>>>>>>>
>>>>>>>
>>>>>>> On Tue, Dec 24, 2013 at 1:19 PM, Keno Fischer <
>>>>>>> kfischer at college.harvard.edu> wrote:
>>>>>>>
>>>>>>>> I have this (as I said, I haven't tried it). It seems to be a
>>>>>>>> different patch.
>>>>>>>>
>>>>>>>>
>>>>>>>> On Tue, Dec 24, 2013 at 11:17 AM, Andrew MacPherson <
>>>>>>>> andrew.macp at gmail.com> wrote:
>>>>>>>>
>>>>>>>>> Hi Keno,
>>>>>>>>>
>>>>>>>>> I found this old patch that hooks into the GDB JIT registration
>>>>>>>>> mechanism which we were planning to use as a starting point:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> http://lists.cs.uiuc.edu/pipermail/lldb-dev/2010-December/000314.html
>>>>>>>>>
>>>>>>>>> If you have anything else we'd love to take a look!
>>>>>>>>>
>>>>>>>>> Cheers,
>>>>>>>>> Andrew
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Tue, Dec 24, 2013 at 8:34 AM, Keno Fischer <
>>>>>>>>> kfischer at college.harvard.edu> wrote:
>>>>>>>>>
>>>>>>>>>> Hi Andrew,
>>>>>>>>>>
>>>>>>>>>> I'm also one of the Julia core developers and the guy currently
>>>>>>>>>> working on
>>>>>>>>>> debugging support. I was given a patch to add MCJIT debugging
>>>>>>>>>> support
>>>>>>>>>> to LLDB with the disclaimer that it probably doesn't work. I
>>>>>>>>>> haven't tried it
>>>>>>>>>> yet, so I can't say how close it is, but it's probably at least a
>>>>>>>>>> starting point.
>>>>>>>>>>
>>>>>>>>>> I'd be happy to coordinate any efforts.
>>>>>>>>>>
>>>>>>>>>> - Keno
>>>>>>>>>>
>>>>>>>>>> _______________________________________________
>>>>>>>>>> lldb-dev mailing list
>>>>>>>>>> lldb-dev at cs.uiuc.edu
>>>>>>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
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