dynup/kpatch — pull request #412 by jpoimboe (2014-09-09 18:40:10+00:00)
Title: support for__key and __warned special static local vars

Add support for the __key and __warned "special" static local variables.
I'm calling them that for lack of a better term, analagous to the
kernel's special sections that we have to deal with.

__warned: Used by WARN_ONCE et al as an indicator as to whether a
message has already been printed. I think it makes sense (and is much
easier) to reset this counter for a given function when replacing the
function, since the user may expect the new function to warn again.

__key: Used by lockdep as an identifier for a given lock initialization
code path (see http://lwn.net/Articles/185666/ for more info). I think
it makes sense (and is much easier) to create a new key for a given
function when replacing the function, because the locking semantics may
have changed, so it makes sense for lockdep to use a new key to validate
the new locking behavior.

So for both __warned and __key static variables, the new version of the
variable should be used when referenced by an included function.

Made the following changes to support these special variables:

- Ignore their suffixes when comparing them in rela_equal, so that gcc
renaming them will not result in a function being marked as changed
just because it referenced a renamed static local

- Don't ever correlate them, so that their new versions will be included
if a changed or new function uses their corresponding symbols

Fixes #402.