Re: Section mismatch in parainstructions

[Randy Dunlap <randy.dunlap@oracle.com>]

On Sun, 10 Dec 2006 16:40:53 -0800 Jeremy Fitzhardinge wrote:

> Randy Dunlap wrote:
> > Is it OK for section .parainstructions to reference
> > exit.text?
> >
> > I'm seeing:
> >
> > WARNING: drivers/net/hamradio/scc.o - Section mismatch: reference to .exit.text: from .parainstructions after '' (at offset 0x0)
> > WARNING: drivers/net/hamradio/scc.o - Section mismatch: reference to .exit.text: from .parainstructions after '' (at offset 0x8)
> >
> > If that's OK, we need a small patch to modpost, as below.
> >   
> 
> What are the semantics of .exit.text?  In principle a paravirtualized
> instruction can appear anywhere, so I think these warnings are bogus. 
> The only concern is if one of these sections disappears before the
> paravirt_ops instruction substitution happens.

Good question.  I don't see much doc on that subject.
Rusty could probably answer that better than me.

Something like this:

.exit.text section(s) can be discarded from built-in (non-modular)
code (or not even loaded at all).

.exit.text section(s) in modules is only loaded when
CONFIG_MODULE_UNLOAD=y.


so what are the .parainstructions text sections for?
Are they for replacing code instructions based on some
condition(s)?  (like <gag> self-modifying code? </gag>)

---
~Randy