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

[Peter Zijlstra]

On Tue, Oct 15, 2019 at 09:28:02AM -0400, Steven Rostedt wrote:
> On Fri, 11 Oct 2019 14:59:03 +0200
> Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> 
> > On Thu, Oct 10, 2019 at 07:28:19PM +0200, Peter Zijlstra wrote:
> > 
> > > Really the best solution is to move all the poking into
> > > ftrace_module_init(), before we mark it RO+X. That's what I'm going to
> > > do for jump_label and static_call as well, I just need to add that extra
> > > notifier callback.  
> > 
> > OK, so I started writing that patch... or rather, I wrote the patch and
> > started on the Changelog when I ran into trouble describing why we need
> > it.
> > 
> > That is, I'm struggling to explain why we cannot flip
> > prepare_coming_module() and complete_formation().
> > 
> > Yes, it breaks ftrace, but I'm thinking that is all it breaks. So let me
> > see if we can cure that.
> 
> You are mainly worried about making text that is executable into
> read-write again. What if we kept my one patch that just changed the
> module in ftrace_module_enable() from read-only to read-write, but
> before we ever set it executable.

This still flips the protections back and forth, which is still really
ugly. And afaict the only reason this is required is that
set_all_modules_text_*() stuff.

So please, instead of tinkering around, lets just kill that horrible
interface and be done with it. There's only 2 users left, fixing those
can't be too hard.