Re: [RFC PATCH 2/2] livepatch: Clear relocation targets on a module removal

[Josh Poimboeuf]

On Thu, Sep 05, 2019 at 01:19:06PM +0200, Jiri Kosina wrote:
> On Thu, 5 Sep 2019, Petr Mladek wrote:
> 
> > > I don't have a number, but it's very common to patch a function which 
> > > uses jump labels or alternatives.
> > 
> > Really? My impression is that both alternatives and jump_labels
> > are used in hot paths. I would expect them mostly in core code
> > that is always loaded.
> > 
> > Alternatives are often used in assembly that we are not able
> > to livepatch anyway.
> > 
> > Or are they spread widely via some macros or inlined functions?
> 
> All the indirect jumps are turned into alternatives when retpolines are in 
> place.

Actually in C code those are done by the compiler as calls/jumps to
__x86_indirect_thunk_*.

But there are still a bunch of paravirt patched instructions and
alternatives used throughout the kernel.

-- 
Josh