x64 machine code and stack frames

Pedro Alves palves@redhat.com
Fri Jan 22 10:37:00 GMT 2016


On 01/22/2016 06:46 AM, Dov Grobgeld wrote:
> Thanks. Indeed it sounds like the right direction. I have to figure
> out how it works in a mixed environment with both static DWARF based
> code as well as dynamically allocated code.
> 
> On Fri, Jan 22, 2016 at 4:27 AM, Matt Rice <ratmice@gmail.com> wrote:
>>
>>
>> On Thu, Jan 21, 2016 at 11:45 AM, Dov Grobgeld <dov.grobgeld@gmail.com>
>> wrote:
>>>
>>> Hello,
>>>
>>> I've inherited some clever x64 machine code for linux that creates an
>>> machine code wrapper around a c-function call. I guess that in higher
>>> language terms the code might be called a decorator or a closure. The
>>> code is functioning well, but with the unfortunate artifact that when
>>> the wrapper is called, it gobbles the stack trace in gdb.
>>>
>>> From what I have learned from the net gdb uses
>>> https://en.wikipedia.org/wiki/DWARF as a guide for separating the
>>> stack frames in the stack. This works well for static code, but
>>> obviously code generated and called at run time isn't registered in
>>> the DWARF framework.
>>>
>>> My question is if there is any way to rescue the stack trace in this
>>> situation?
>>
>>
>> While i haven't really used it before & can't comment on the particulars,
>> It sounds like you should be using the jit interface to make gdb aware of
>> the symbols generated at runtime.
>>
>> https://sourceware.org/gdb/onlinedocs/gdb/JIT-Interface.html

And for unwinding itself, the new Python unwinder API is something to look at
too, if you want to try to avoid DWARF:

  https://sourceware.org/gdb/current/onlinedocs/gdb/Unwinding-Frames-in-Python.html

Thanks,
Pedro Alves



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