linux-kernel - Re: [PATCH v6 11/17] static

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Date:   Fri, 10 Jul 2020 18:42:29 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, mhiramat@...nel.org,
        bristot@...hat.com, jbaron@...mai.com,
        torvalds@...ux-foundation.org, tglx@...utronix.de,
        mingo@...nel.org, namit@...are.com, hpa@...or.com, luto@...nel.org,
        ard.biesheuvel@...aro.org, jpoimboe@...hat.com,
        pbonzini@...hat.com, mathieu.desnoyers@...icios.com,
        linux@...musvillemoes.dk
Subject: Re: [PATCH v6 11/17] static_call: Simple self-test

On Fri, 10 Jul 2020 15:38:42 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  arch/Kconfig         |    6 ++++++
>  kernel/static_call.c |   28 ++++++++++++++++++++++++++++
>  2 files changed, 34 insertions(+)
> 
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -103,6 +103,12 @@ config STATIC_KEYS_SELFTEST
>  	help
>  	  Boot time self-test of the branch patching code.
>  
> +config STATIC_CALL_SELFTEST
> +	bool "Static call selftest"
> +	depends on HAVE_STATIC_CALL
> +	help
> +	  Boot time self-test of the call patching code.
> +
>  config OPTPROBES
>  	def_bool y
>  	depends on KPROBES && HAVE_OPTPROBES
> --- a/kernel/static_call.c
> +++ b/kernel/static_call.c
> @@ -364,3 +364,31 @@ static void __init static_call_init(void
>  #endif
>  }
>  early_initcall(static_call_init);
> +
> +#ifdef CONFIG_STATIC_CALL_SELFTEST
> +
> +static int func_a(int x)
> +{
> +	return x+1;
> +}
> +
> +static int func_b(int x)
> +{
> +	return x+2;
> +}
> +
> +DEFINE_STATIC_CALL(sc_selftest, func_a);
> +
> +static int __init test_static_call_init(void)
> +{
> +	WARN_ON(static_call(sc_selftest)(2) != 3);
> +	static_call_update(sc_selftest, &func_b);
> +	WARN_ON(static_call(sc_selftest)(2) != 4);
> +	static_call_update(sc_selftest, &func_a);
> +	WARN_ON(static_call(sc_selftest)(2) != 3);
> +
> +	return 0;
> +}

I wonder if this would be better if we were testing the same static call each time?

static int __init run_static_call(int val)
{
	return static_call(sc_selftest)(val);
}

static struct {
	int (*func)(int);
	int val;
	int expect;
} static_call_data [] = {
	{ NULL, 2, 3 }
	( func_b, 2 , 4},
	{ func_a, 2, 3}
} __initdata;

static int __init test_static_call_init(void)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(static_call_data); i++ ) {
		if (static_call_data[i].func)
			static_call_update(sc_selftest, static_call_data[i].func);
		WARN_ON(run_static_call(static_call_data[i].val) != static_call_data[i].expect);
	}

	return 0;
}

-- Steve


> +early_initcall(test_static_call_init);
> +
> +#endif /* CONFIG_STATIC_CALL_SELFTEST */
>