tracefs splats in lockdown=confidentiality mode

[Steven Rostedt]

On Mon, 2 Dec 2019 15:31:52 -0800
Matthew Garrett <mjg59 at google.com> wrote:

> On Fri, Nov 1, 2019 at 2:08 PM dann frazier <dann.frazier at canonical.com> wrote:
> 
> > [    1.763630] Lockdown: swapper/0: use of tracefs is restricted; see man kernel_lockdown.7  
> 
> This is expected.
> 
> > [    2.913934] ------------[ cut here ]------------
> > [    2.918435] Could not register function stat for cpu 0
> > [    2.923717] WARNING: CPU: 1 PID: 1 at kernel/trace/ftrace.c:987 ftrace_init_tracefs_toplevel+0x168/0x1bc  
> 
> This is not. I'll look into it.

I think it has to do with ftrace triggering WARN_ON() if it fails to
create files. We don't want this to happen if it fails because of
lockdown.

I'm already looking into it.

Thanks!

-- Steve