[PATCH v4 1/2] function_graph: Support recording and printing the return value of function

[Steven Rostedt]

On Wed, 15 Mar 2023 14:49:11 +0100
Peter Zijlstra <peterz at infradead.org> wrote:

> > diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S
> > index 1265ad519249..35ac9c58dc77 100644
> > --- a/arch/x86/kernel/ftrace_64.S
> > +++ b/arch/x86/kernel/ftrace_64.S
> > @@ -348,6 +348,10 @@ SYM_CODE_START(return_to_handler)
> >  	movq %rax, (%rsp)
> >  	movq %rdx, 8(%rsp)
> >  	movq %rbp, %rdi
> > +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL
> > +	/* Pass the function return value to ftrace_return_to_handler */
> > +	movq %rax, %rsi
> > +#endif
> >  
> >  	call ftrace_return_to_handler  
> 
> What about the case of double register return values (when the value
> is returned in the A,D pair) ?

Is there anything that does that in 64 bit kernels?

-- Steve