Stack unwinder for SA

[David Holmes]

On 25/01/2021 12:41 pm, Yasumasa Suenaga wrote:
> Hi all,
> 
> Chris and I discussed about fixing JDK-8245234 to see all mixed stacks 
> via `jhsdb jstack --mixed`.
> In the discussion, we agree to use stack unwinder, but we haven't yet 
> decided which library to use.
> Can you suggest the stack unwinder for SA?
> 
> I fixed similar issue in JDK-8234624 to understand DWARF in SA for 
> Linux, however it does not support DWARF completely because it is too 
> complex to implement by scratch.
> AMD64 SysV ABI [1] says DWARF is used for stack unwinding. So we need to 
> support DWARF completely if we want to unwind.
> 
> There are some stack unwinder. I think libunwind [2] is suitable for 
> this purpose, however I'm not sure it is the best solution.
> And also I saw similar issue on Windows because we cannot depend on base 
> pointer (like SA) in Windows x64 [3]. So I want to use the library which 
> is support both Linux and Windows.
> 
> We also think introducing stack unwinder helps improving native call 
> stacks in hs_err log. It will help troubleshooters.

Immediate reaction to this part is that I would not want third-party 
libraries getting involved in hs_err file generation. Given we often do 
this from a signal handling context, it would be far too risky IMO.

Cheers,
David
-----

> 
> I want to hear your opinions!
> 
> 
> Thanks,
> 
> Yasumasa
> 
> 
> [1] 
> https://software.intel.com/sites/default/files/article/402129/mpx-linux64-abi.pdf 
> 
> [2] https://github.com/libunwind/libunwind
> [3] 
> https://docs.microsoft.com/en-us/cpp/build/exception-handling-x64#unwind-procedure 
>