Re: [PATCH][v4] livepatch/ppc: Enable livepatching on powerpc

On Fri, Mar 04, 2016 at 02:01:37PM +0100, Petr Mladek wrote:

Do I understand it correctly that we could not patch functions that
pass arguments on the stack with this implementation? If yes, how hard
would be to get it working, please? At least, it would be great to
catch this problem and handle it with grace. Otherwise, it might
be hard to debug.

No, those functions only require special attention.
I needed _any_ location to store the caller's TOC;
and the stack is thread-safe and recursion-safe.
The current caller's frame is already full so I had
to create a new one.

A patch function could e.g. grab that TOC value in a
prologue and then pop that stack frame. Or it could
add those 32 bytes to the assumed arguments' stack offsets.

quoted

Where shall we put this warning?

Sadly, we do not have any Documentation/livepatch/ yet/.
I still hope that we could handle it somehow in the code.

I really think some documentation would be good, a live patch
howto for a start...

	Torsten