On Mon, Feb 08, 2021 at 10:02:06AM -0500, Steven Rostedt wrote:
> On Sun, 7 Feb 2021 16:45:40 -0600
> Josh Poimboeuf <jpoim...@redhat.com> wrote:
>
> > > I do suspect involved people should start thinking about how they want
> > > to deal with functions starting with
> > >
> > > endbr64
> > > call __fentry__
> > >
> > > instead of the call being at the very top of the function.
> >
> > FWIW, objtool's already fine with it (otherwise we would have discovered
> > the need to disable fcf-protection much sooner).
>
> And this doesn't really affect tracing (note, another user that might be
> affected is live kernel patching).
Good point, livepatch is indeed affected. Is there a better way to get
the "call __fentry__" address for a given function?
/*
* Convert a function address into the appropriate ftrace location.
*
* Usually this is just the address of the function, but on some architectures
* it's more complicated so allow them to provide a custom behaviour.
*/
#ifndef klp_get_ftrace_location
static unsigned long klp_get_ftrace_location(unsigned long faddr)
{
return faddr;
}
#endif
--
Josh
