linux-kernel - Re: [PATCH] arm64: Add __exception_irq_entry definition for function graph

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Message-ID: <20150812150232.GI23540@arm.com>
Date:	Wed, 12 Aug 2015 16:02:32 +0100
From:	Will Deacon <will.deacon@....com>
To:	Jungseok Lee <jungseoklee85@...il.com>
Cc:	Catalin Marinas <Catalin.Marinas@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	AKASHI Takahiro <takahiro.akashi@...aro.org>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Rabin Vincent <rabin@....in>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] arm64: Add __exception_irq_entry definition for function
 graph

On Wed, Aug 12, 2015 at 03:16:19PM +0100, Jungseok Lee wrote:
> The gic_handle_irq() is defined with __exception_irq_entry attribute.
> A single remaining work is to add its definition as ARM did. Below
> shows how function graph data is changed with these hunks.

[...]

> diff --git a/arch/arm64/include/asm/traps.h b/arch/arm64/include/asm/traps.h
> index 232e4ba..0cc2f29 100644
> --- a/arch/arm64/include/asm/traps.h
> +++ b/arch/arm64/include/asm/traps.h
> @@ -34,13 +34,32 @@ struct undef_hook {
>  void register_undef_hook(struct undef_hook *hook);
>  void unregister_undef_hook(struct undef_hook *hook);
>  
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +static inline int __in_irqentry_text(unsigned long ptr)
> +{
> +	extern char __irqentry_text_start[];
> +	extern char __irqentry_text_end[];
> +
> +	return ptr >= (unsigned long)&__irqentry_text_start &&
> +	       ptr < (unsigned long)&__irqentry_text_end;
> +}
> +#else
> +static inline int __in_irqentry_text(unsigned long ptr)
> +{
> +	return 0;
> +}
> +#endif
> +
>  static inline int in_exception_text(unsigned long ptr)
>  {
>  	extern char __exception_text_start[];
>  	extern char __exception_text_end[];
> +	int in;
> +
> +	in = ptr >= (unsigned long)&__exception_text_start &&
> +	     ptr < (unsigned long)&__exception_text_end;
>  
> -	return ptr >= (unsigned long)&__exception_text_start &&
> -	       ptr < (unsigned long)&__exception_text_end;
> +	return in ? : __in_irqentry_text(ptr);
>  }

On arm64, this function is only called from dump_backtrace, so I'm
struggling to see why this change makes any difference to the ftrace
output.

What am I missing?

Will
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