On Thu, 27 Jun 2019, Steven Rostedt wrote:
> On Thu, 27 Jun 2019 17:47:29 -0500
> > Releasing the lock in a separate function seems a bit surprising and
> > fragile, would it be possible to do something like this instead?
> >
> > diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> > index b38c388d1087..89ea1af6fd13 100644
> > --- a/arch/x86/kernel/ftrace.c
> > +++ b/arch/x86/kernel/ftrace.c
> > @@ -37,15 +37,21 @@
> > int ftrace_arch_code_modify_prepare(void)
> > {
> > mutex_lock(&text_mutex);
> > +
> > set_kernel_text_rw();
> > set_all_modules_text_rw();
> > +
> > + mutex_unlock(&text_mutex);
> > return 0;
> > }
> >
> > int ftrace_arch_code_modify_post_process(void)
> > {
> > + mutex_lock(&text_mutex);
> > +
> > set_all_modules_text_ro();
> > set_kernel_text_ro();
> > +
> > mutex_unlock(&text_mutex);
> > return 0;
> > }
>
> I agree with Josh on this. As the original bug was the race between
> ftrace and live patching / modules changing the text from ro to rw and
> vice versa. Just protecting the update to the text permissions is more
> robust, and should be more self documenting when we need to handle
> other architectures for this.
How is that supposed to work?
ftrace
prepare()
setrw()
setro()
patch <- FAIL
Thanks,
tglx
