Re: [PATCHv3] arm: ftrace: Adds support for CONFIG_DYNAMIC_FTRACE_WITH_REGS

[Russell King - ARM Linux]

On Thu, Feb 09, 2017 at 04:38:32PM +0100, Jean-Jacques Hiblot wrote:
> 2017-02-07 23:57 GMT+01:00 Abel Vesa <abelvesa@xxxxxxxxx>:
> > +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> > +.macro __ftrace_graph_regs_caller
> > +
> > +       sub     r0, fp, #4              @ lr of instrumented routine (parent)
> > +
> > +       @ called from __ftrace_regs_caller
> > +       ldr     r1, [sp, #56]           @ instrumented routine (func)
> > +       mcount_adjust_addr      r1, r1
> > +
> > +       sub     r2, r0, #4              @ frame pointer
> why not mov r2, fp  ?

	r0 = fp - 4
	r2 = r0 - 4

therefore

	r2 = (fp - 4) - 4
	r2 = fp - 8, not r2 = fp

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