[Crash-utility] reliable x86_64 (and x86) kernel stack trace support

[Dave Anderson]

Good news...

Jan Beulich of Novell has posted a 3-part patch for introducing
reliable back tracing (from within the kernel) for x86_64 and x86:

  [PATCH 1/3] reliable stack trace support
  http://www.uwsg.indiana.edu/hypermail/linux/kernel/0605.2/0102.html

It looks very much like the ia64 implementation, but done much more
generically.  Unfortunately, at least the x86_64 version doesn't cross the
interrupt stack to process stack boundary.  He doesn't mention about
transitioning from the x86_64 exception stacks to the process or interrupt
stacks, but I'm presuming that wouldn't work either.  And I would presume
that x86 stack transitions also would not work, since AFAICT the code that
would make the stack transitions would be in the generic code section.

Anyway, this is very promising for the future.  Not only may we be able to
supplement the crash utility's low-budget x86_64 backtracer, but perhaps
even the heavily-patched LKCD-based x86 version as well.

Dave