[PATCH 1/2] arm64: Fix static use of function graph

[Russell King - ARM Linux]

On Thu, Nov 02, 2017 at 01:43:07PM +0900, AKASHI Takahiro wrote:
> On Wed, Nov 01, 2017 at 02:33:43PM +0000, Julien Thierry wrote:
> > Function graph does not work currently when CONFIG_DYNAMIC_TRACE is not
> > set. This is because ftrace_function_trace is not always set to ftrace_stub
> > when function_graph is in use.
> > 
> > Do not skip checking of graph tracer functions when ftrace_function_trace
> > is set.
> > 
> > Signed-off-by: Julien Thierry <julien.thierry at arm.com>
> > Cc: Catalin Marinas <catalin.marinas at arm.com>
> > Cc: Will Deacon <will.deacon at arm.com>
> > Cc: Mark Rutland <mark.rutland at arm.com>
> > Cc: AKASHI Takahiro <takahiro.akashi at linaro.org>
> 
> Reviewed-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
> 
> I think that arm has the same issue, hoping the following patch
> will fix it:
> ===
> >From e25bcf50d1acde698285a0c64f72d97f8b17e3fb Mon Sep 17 00:00:00 2001
> From: AKASHI Takahiro <takahiro.akashi at linaro.org>
> Date: Thu, 2 Nov 2017 11:35:04 +0900
> Subject: [PATCH] arm: ftrace: function_graph with DYNAMIC_FTRACE
> 
> ---
>  arch/arm/kernel/entry-ftrace.S | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S
> index efcd9f25a14b..ef94c73ad996 100644
> --- a/arch/arm/kernel/entry-ftrace.S
> +++ b/arch/arm/kernel/entry-ftrace.S
> @@ -68,8 +68,12 @@
>  	ldr	r2, [r0]
>  	adr	r0, .Lftrace_stub
>  	cmp	r0, r2
> -	bne	1f
> +	beq	1f
>  
> + 	mcount_get_lr	r1			@ lr of instrumented func
> +	mcount_adjust_addr	r0, lr		@ instrumented function
> +	blx	r2

NAK.  Not all CPUs support "blx".  I don't see why you'd make this
gratuitous change when just moving code around.  Please separate
your changes in future.

-- 
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