linux-kernel - Re: [PATCH 2/3 v2] kprobes/trace: Fix kprobe selftest for gcc 4.6

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Date:	Wed, 08 Jun 2011 12:45:30 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	David Daney <ddaney@...iumnetworks.com>,
	yrl.pp-manager.tt@...achi.com
Subject: Re: [PATCH 2/3 v2] kprobes/trace: Fix kprobe selftest for gcc 4.6

(2011/06/08 6:29), Steven Rostedt wrote:
> From: Steven Rostedt <srostedt@...hat.com>
> 
> With gcc 4.6, the self test kprobe function:
> 
>  kprobe_trace_selftest_target()
> 
> is optimized such that kallsyms does not list it. The kprobes
> test uses this function to insert a probe and test it. But
> it will fail the test if the function is not listed in kallsyms.
> 
> Adding a __used annotation keeps the symbol in the kallsyms table.

Thanks Steven and David,

That's good to me!

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>

> 
> Suggested-by: David Daney <ddaney@...iumnetworks.com>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> ---
>  kernel/trace/trace_kprobe.c |    8 ++++++--
>  1 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index f925c45..27d13b3 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -1870,8 +1870,12 @@ fs_initcall(init_kprobe_trace);
>  
>  #ifdef CONFIG_FTRACE_STARTUP_TEST
>  
> -static int kprobe_trace_selftest_target(int a1, int a2, int a3,
> -					int a4, int a5, int a6)
> +/*
> + * The "__used" keeps gcc from removing the function symbol
> + * from the kallsyms table.
> + */
> +static __used int kprobe_trace_selftest_target(int a1, int a2, int a3,
> +					       int a4, int a5, int a6)
>  {
>  	return a1 + a2 + a3 + a4 + a5 + a6;
>  }


-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
--
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