scripts/gdb: add container_of helper and convenience function

scripts/gdb: add container_of helper and convenience function

Provide an internal helper with container_of semantics.  As type lookups
are very slow in gdb-python and we need a type "long" for this, cache the
reference to this type object.  Then export the helper also as a
convenience function form use at the gdb command line.

Signed-off-by: Jan Kiszka <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Jason Wessel <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Ben Widawsky <[email protected]>
Cc: Borislav Petkov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>