[lldb-dev] Port LLDB to ppc64le (ABIv2) on linux

Howard Hellyer via lldb-dev lldb-dev at lists.llvm.org
Thu Jul 6 09:04:02 PDT 2017

> > Hi Gustavo,
> > 
> > Were you interested in support for live debugging via ptrace or 
> > from core files? (Or both!)
> Mainly live debugging, but I have the feeling that implementing 
> post-mortem wouldn't be such a hassle afterwards. (register read/
> write, stack walk... they would all be done at this point).

I think on Linux ELF and DWARF take care of most of the issues, my changes 
were mostly to do with making LLDB aware that ppc64 and little endian was 
an option and sending it down the right code paths. Once it knew the 
registers for that combination I think it could cope with walking the 

> > Live debugging looked a bit more complicated but that's probably 
> > most of my experience has been with post-mortem debugging. I think I
> > stopped work on the core file support because I didn't have the time 
> > learn about the live debugging side and it didn't seem to make sense 
> > add core file support without live debug.
> Wait. As far as I understood, LLDB already supports ppc64 big 
> endian, right? (particularly the ppc970 model) Plenty of things 
> changed since then but I guess I can use it as a reference (despite 
> endianness, of course).

Yes, but I think it supports ppc64 on FreeBSD. The register context code 
in source/Plugins/Process/Linux and source/Plugins/Process/FreeBSD 
suggests that's the case. I suspect you can use the FreeBSD code as a 
reference. However this is where it goes outside what I'm familiar with 
and you are probably better off asking someone else for more details. 
There's a RegisterContextCorePOSIX_powerpc in 
source/Plugins/Process/elf-core/ on the post-mortem side already which 
made the Linux core dump support easier.
Howard Hellyer
J9 RAS Developer
IBM Runtime Technologies, IBM Systems
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number 
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
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