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Commit ce5af3ba authored by Jon Medhurst's avatar Jon Medhurst
Browse files

ARM: kprobes: Add some benchmarking to test module 



These benchmarks show the basic speed of kprobes and verify the success
of optimisations done to the emulation of typical function entry
instructions (i.e. push/stmdb).

Signed-off-by: default avatarJon Medhurst <tixy@yxit.co.uk>
Acked-by: default avatarNicolas Pitre <nicolas.pitre@linaro.org>
parent 963780df

arch/arm/kernel/kprobes-test.c

+161 −0
Original line number Diff line number Diff line
@@ -185,6 +185,9 @@ 
#include "kprobes-test.h"





#define BENCHMARKING	1





/*

 * Test basic API

 */
@@ -443,6 +446,157 @@ static int run_api_tests(long (*func)(long, long)) 
}





/*

 * Benchmarking

 */



#if BENCHMARKING



static void __naked benchmark_nop(void)

{

	__asm__ __volatile__ (

		"nop		\n\t"

		"bx	lr"

	);

}



#ifdef CONFIG_THUMB2_KERNEL

#define wide ".w"

#else

#define wide

#endif



static void __naked benchmark_pushpop1(void)

{

	__asm__ __volatile__ (

		"stmdb"wide"	sp!, {r3-r11,lr}  \n\t"

		"ldmia"wide"	sp!, {r3-r11,pc}"

	);

}



static void __naked benchmark_pushpop2(void)

{

	__asm__ __volatile__ (

		"stmdb"wide"	sp!, {r0-r8,lr}  \n\t"

		"ldmia"wide"	sp!, {r0-r8,pc}"

	);

}



static void __naked benchmark_pushpop3(void)

{

	__asm__ __volatile__ (

		"stmdb"wide"	sp!, {r4,lr}  \n\t"

		"ldmia"wide"	sp!, {r4,pc}"

	);

}



static void __naked benchmark_pushpop4(void)

{

	__asm__ __volatile__ (

		"stmdb"wide"	sp!, {r0,lr}  \n\t"

		"ldmia"wide"	sp!, {r0,pc}"

	);

}





#ifdef CONFIG_THUMB2_KERNEL



static void __naked benchmark_pushpop_thumb(void)

{

	__asm__ __volatile__ (

		"push.n	{r0-r7,lr}  \n\t"

		"pop.n	{r0-r7,pc}"

	);

}



#endif



static int __kprobes

benchmark_pre_handler(struct kprobe *p, struct pt_regs *regs)

{

	return 0;

}



static int benchmark(void(*fn)(void))

{

	unsigned n, i, t, t0;



	for (n = 1000; ; n *= 2) {

		t0 = sched_clock();

		for (i = n; i > 0; --i)

			fn();

		t = sched_clock() - t0;

		if (t >= 250000000)

			break; /* Stop once we took more than 0.25 seconds */

	}

	return t / n; /* Time for one iteration in nanoseconds */

};



static int kprobe_benchmark(void(*fn)(void), unsigned offset)

{

	struct kprobe k = {

		.addr		= (kprobe_opcode_t *)((uintptr_t)fn + offset),

		.pre_handler	= benchmark_pre_handler,

	};



	int ret = register_kprobe(&k);

	if (ret < 0) {

		pr_err("FAIL: register_kprobe failed with %d\n", ret);

		return ret;

	}



	ret = benchmark(fn);



	unregister_kprobe(&k);

	return ret;

};



struct benchmarks {

	void		(*fn)(void);

	unsigned	offset;

	const char	*title;

};



static int run_benchmarks(void)

{

	int ret;

	struct benchmarks list[] = {

		{&benchmark_nop, 0, "nop"},

		/*

		 * benchmark_pushpop{1,3} will have the optimised

		 * instruction emulation, whilst benchmark_pushpop{2,4} will

		 * be the equivalent unoptimised instructions.

		 */

		{&benchmark_pushpop1, 0, "stmdb	sp!, {r3-r11,lr}"},

		{&benchmark_pushpop1, 4, "ldmia	sp!, {r3-r11,pc}"},

		{&benchmark_pushpop2, 0, "stmdb	sp!, {r0-r8,lr}"},

		{&benchmark_pushpop2, 4, "ldmia	sp!, {r0-r8,pc}"},

		{&benchmark_pushpop3, 0, "stmdb	sp!, {r4,lr}"},

		{&benchmark_pushpop3, 4, "ldmia	sp!, {r4,pc}"},

		{&benchmark_pushpop4, 0, "stmdb	sp!, {r0,lr}"},

		{&benchmark_pushpop4, 4, "ldmia	sp!, {r0,pc}"},

#ifdef CONFIG_THUMB2_KERNEL

		{&benchmark_pushpop_thumb, 0, "push.n	{r0-r7,lr}"},

		{&benchmark_pushpop_thumb, 2, "pop.n	{r0-r7,pc}"},

#endif

		{0}

	};



	struct benchmarks *b;

	for (b = list; b->fn; ++b) {

		ret = kprobe_benchmark(b->fn, b->offset);

		if (ret < 0)

			return ret;

		pr_info("    %dns for kprobe %s\n", ret, b->title);

	}



	pr_info("\n");

	return 0;

}



#endif /* BENCHMARKING */





/*

 * Decoding table self-consistency tests

 */
@@ -1526,6 +1680,13 @@ static int __init run_all_tests(void) 
		goto out;

	}



#if BENCHMARKING

	pr_info("Benchmarks\n");

	ret = run_benchmarks();

	if (ret)

		goto out;

#endif



#if __LINUX_ARM_ARCH__ >= 7

	/* We are able to run all test cases so coverage should be complete */

	if (coverage_fail) {