[Crash-utility] Crash support for kASLR

[Dave Anderson]

----- Original Message -----
> I'm trying to add crash support for kdumps from kASLR'd kernels.  I've
> got it working with a few small changes and I wanted to solicit
> comments before sending a patch.

Excellent!
 
> 1) The --reloc flag appears to specify an offset to be subtracted from
> the loaded address, when the aslr offset is added.  It's annoying to
> try to specify negative numbers on the command line, so I'd like to
> add another argument --aslr which is the same as --reloc but negates
> the value.

Not a problem.  In fact, since they really are different concepts, I'd 
prefer it.  But can you make it --kalsr?

A couple questions -- how would the user know what the offset is?

And I had thought that the upstream discussion was geared towards
making it work automatically -- at least with kdump dumpfiles -- such
that the kASLR offset would be made a VMCOREINFO item?

> 2) There are some symbols which should not be relocated.  Specifically
> the per_cpu section symbols are zero based offsets which should not
> have the offset apply.  Additionally there are VDSO symbols which are
> fixed even with kASLR enabled.  To fix this I'd like to add code to
> iterate through the section and find the end of the last section and
> only apply the relocation value to values after the start of text but
> before the end of the last section.

Right...

> thanks,
> Andy

Good to hear from you -- I figured that when I saw your subscription 
request, with it being the first/only "google.com" address ever, that
something interesting was forthcoming...

Thanks,
  Dave Anderson