Re: [PATCH v5 05/12] x86/retpoline/ftrace: Convert ftrace assembler indirect jumps

[Thomas Gleixner]

On Sat, 6 Jan 2018, Linus Torvalds wrote:

> On Sat, Jan 6, 2018 at 3:49 AM, David Woodhouse <dwmw@xxxxxxxxxxxx> wrote:
> >
> > -       call    *ftrace_trace_function
> > +       movl    ftrace_trace_function, %ecx
> > +       NOSPEC_CALL %ecx
> 
> Can't we just do
> 
>     NOSPEC_CALL ftrace_trace_function
> 
> now?
> 
> [ Goes off and looks ]
> 
> Oh. The AMD lfence version wants a register. Oh well.

The register load could be put into the macro itself, though we need to
supply a scratch register

     NOSPEC_CALL ftrace_trace_function scratch_reg=%ecx

Whether thats much better, I don't know.

Thanks,

	tglx