Re: [PATCH v2 4/5] Provide access to non SEC_HAS_CONTENTS core file sections

[Pedro Alves <palves@redhat.com>]

On 5/21/20 8:50 AM, Kevin Buettner via Gdb-patches wrote:
> On Wed, 20 May 2020 17:45:28 +0100
> Pedro Alves <palves@redhat.com> wrote:
> On Linux, we're able to do "info proc mappings" when looking at a
> corefile.  Linux core files include a .note.linuxcore.file/pid section
> which contain the map data that you see when running "info proc
> mappings".
> 
> It may be possible to use these mappings to provide a more accurate
> view of memory contents when working with a core file.  In addition
> to file backed data that we already know about from the executable and
> shared libraries, there may be additional file backed data that can
> be found via files listed in the .note section mentioned earlier.  Or,
> as I found while investigating that one of those weird F27 mappings,
> there may be data from a shared library which can't be found in
> what GDB knows about when loading the shared library.  (In that
> particular case, the memory region in question contained some
> vtable data prior to being remapped - though I'm guessing about
> the remapping bit.)

Yeah, that's a good idea.

> 
> If you think it worth pursuing, I can look at using the core-provided
> proc mapping information to provide a more accurate view of memory
> when looking at a core dump.

I think it's worth pursuing.  If we have proc mappings data, we could
only read from the exec file first if the mapping is file-backed.
That sounds like would plug the ambiguity.

> 
> If I do this, is it still worth pushing this v2 series first?  Or should
> it wait until I attempt to incorporate info from the .note section?

I'd say give it a try, see if it would be too complicated.
If it isn't, then I think it would be nice to merge it all
together.

Thanks,
Pedro Alves