Re: [PATCH v3 5/6] x86/ftrace: Use text_poke()

[Peter Zijlstra]

On Tue, Oct 15, 2019 at 03:56:34PM +0200, Peter Zijlstra wrote:
> On Tue, Oct 15, 2019 at 03:07:40PM +0200, Jessica Yu wrote:

> > > Once this ftrace thing is sorted, we'll change x86 to _refuse_ to make
> > > executable (kernel) memory writable.
> > 
> > Not sure if relevant, but just thought I'd clarify: IIRC,
> > klp_module_coming() is not poking the coming module, but it calls
> > module_enable_ro() on itself (the livepatch module) so it can apply
> > relocations and such on the new code, which lives inside the livepatch
> > module, and it needs to possibly do this numerous times over the
> > lifetime of the patch module for any coming module it is responsible
> > for patching (i.e., call module_enable_ro() on the patch module, not
> > necessarily the coming module). So I am not be sure why
> > klp_module_coming() should be moved before complete_formation(). I
> > hope I'm remembering the details correctly, livepatch folks feel free
> > to chime in if I'm incorrect here.
> 
> You mean it does module_disable_ro() ? That would be broken and it needs
> to be fixed. Can some livepatch person explain what it does and why?

mbenes confirmed; what would be needed is for the live-patch module to
have all module dependent parts to be in their own section and have the
sections be page-aligned. Then we can do the protection on sections
instead of on the whole module.

Damn, and I thought I was so close to getting W^X sorted :/