Re: [PATCH v4 15/16] module: Move where we mark modules RO,X

[Peter Zijlstra]

On Fri, Oct 25, 2019 at 08:44:56AM +0200, Petr Mladek wrote:
> On Thu 2019-10-24 15:16:34, Peter Zijlstra wrote:

> > Right, that really should be able to run early. Esp. after commit
> > 
> >   11e86dc7f274 ("x86/paravirt: Detect over-sized patching bugs in paravirt_patch_call()")
> > 
> > paravirt patching is unconditional. We _never_ run with the indirect
> > call except very early boot, but modules should have them patched way
> > before their init section runs.
> > 
> > We rely on this for spectre-v2 and friends.
> 
> Livepatching has the same requirement. The module code has to be fully
> livepatched before the module gets actually used.

Right, and that is just saying that all paravirt RELAs (pv_ops) can
basically be deleted from modules.

Which avoids the reported problem in yet another way.

> It means before mod->init() is called and before the module is moved
> into MODULE_STATE_LIVE state.

Funny thing, currently ftrace is running code before all that. It runs
code before klp_module_coming(), before jump_label patching.

My other patch in this thread fixes that.