On Wed, Mar 09, 2016 at 11:13:05AM +0100, Jiri Kosina wrote:

On Wed, 9 Mar 2016, Torsten Duwe wrote:

quoted

was my first choice. Arguments on the stack? I thought we'll deal with them
once we get there (e.g. _really_ need to patch a varargs function or one
with a silly signature).

Well, the problem is, once such need arises, it's too late already.

No, not if it's documented.

You need to be able to patch the kernels which are already out there, 
running on machines potentially for ages once all of a sudden there is a 
CVE for >8args / varargs function.

Then you'd need a solution like I sent out yesterday, with a pre-prologue
caller that pops the extra frame, so the replacement can be more straight-
forward. Or you can just deal with the shifted offsets in the replacement.

I'll try to demonstrate the alternative. That would then be required for
_all_ replacement functions. Or can the live patching framework differentiate
and tell ftrace_caller whether to place a stack frame or not?

Miroslav? Petr? Can we have 2 sorts of replacement functions?

	Torsten