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Commit 8c1c9356 authored by Ananth N Mavinakayanahalli's avatar Ananth N Mavinakayanahalli Committed by Ingo Molnar
Browse files

x86: kprobes: add kprobes smoke tests that run on boot 



Here is a quick and naive smoke test for kprobes. This is intended to
just verify if some unrelated change broke the *probes subsystem. It is
self contained, architecture agnostic and isn't of any great use by itself.

This needs to be built in the kernel and runs a basic set of tests to
verify if kprobes, jprobes and kretprobes run fine on the kernel. In case
of an error, it'll print out a message with a "BUG" prefix.

This is a start; we intend to add more tests to this bucket over time.

Thanks to Jim Keniston and Masami Hiramatsu for comments and suggestions.

Tested on x86 (32/64) and powerpc.

Signed-off-by: default avatarAnanth N Mavinakayanahalli <ananth@in.ibm.com>
Acked-by: default avatarMasami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 3334052a

include/linux/kprobes.h

+10 −0
Original line number Diff line number Diff line
@@ -182,6 +182,15 @@ static inline void kretprobe_assert(struct kretprobe_instance *ri, 
	}

}



#ifdef CONFIG_KPROBES_SANITY_TEST

extern int init_test_probes(void);

#else

static inline int init_test_probes(void)

{

	return 0;

}

#endif /* CONFIG_KPROBES_SANITY_TEST */



extern spinlock_t kretprobe_lock;

extern struct mutex kprobe_mutex;

extern int arch_prepare_kprobe(struct kprobe *p);
@@ -227,6 +236,7 @@ void unregister_kretprobe(struct kretprobe *rp); 


void kprobe_flush_task(struct task_struct *tk);

void recycle_rp_inst(struct kretprobe_instance *ri, struct hlist_head *head);



#else /* CONFIG_KPROBES */



#define __kprobes	/**/

kernel/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ obj-$(CONFIG_CPUSETS) += cpuset.o 
obj-$(CONFIG_CGROUP_NS) += ns_cgroup.o

obj-$(CONFIG_IKCONFIG) += configs.o

obj-$(CONFIG_STOP_MACHINE) += stop_machine.o

obj-$(CONFIG_KPROBES_SANITY_TEST) += test_kprobes.o

obj-$(CONFIG_AUDIT) += audit.o auditfilter.o

obj-$(CONFIG_AUDITSYSCALL) += auditsc.o

obj-$(CONFIG_AUDIT_TREE) += audit_tree.o

kernel/kprobes.c

+2 −0
Original line number Diff line number Diff line
@@ -824,6 +824,8 @@ static int __init init_kprobes(void) 
	if (!err)

		err = register_die_notifier(&kprobe_exceptions_nb);



	if (!err)

		init_test_probes();

	return err;

}

kernel/test_kprobes.c

0 → 100644
+216 −0
Original line number Diff line number Diff line 
/*

 * test_kprobes.c - simple sanity test for *probes

 *

 * Copyright IBM Corp. 2008

 *

 * This program is free software;  you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 2 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it would be useful, but

 * WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See

 * the GNU General Public License for more details.

 */



#include <linux/kernel.h>

#include <linux/kprobes.h>

#include <linux/random.h>



#define div_factor 3



static u32 rand1, preh_val, posth_val, jph_val;

static int errors, handler_errors, num_tests;



static noinline u32 kprobe_target(u32 value)

{

	/*

	 * gcc ignores noinline on some architectures unless we stuff

	 * sufficient lard into the function. The get_kprobe() here is

	 * just for that.

	 *

	 * NOTE: We aren't concerned about the correctness of get_kprobe()

	 * here; hence, this call is neither under !preempt nor with the

	 * kprobe_mutex held. This is fine(tm)

	 */

	if (get_kprobe((void *)0xdeadbeef))

		printk(KERN_INFO "Kprobe smoke test: probe on 0xdeadbeef!\n");



	return (value / div_factor);

}



static int kp_pre_handler(struct kprobe *p, struct pt_regs *regs)

{

	preh_val = (rand1 / div_factor);

	return 0;

}



static void kp_post_handler(struct kprobe *p, struct pt_regs *regs,

		unsigned long flags)

{

	if (preh_val != (rand1 / div_factor)) {

		handler_errors++;

		printk(KERN_ERR "Kprobe smoke test failed: "

				"incorrect value in post_handler\n");

	}

	posth_val = preh_val + div_factor;

}



static struct kprobe kp = {

	.symbol_name = "kprobe_target",

	.pre_handler = kp_pre_handler,

	.post_handler = kp_post_handler

};



static int test_kprobe(void)

{

	int ret;



	ret = register_kprobe(&kp);

	if (ret < 0) {

		printk(KERN_ERR "Kprobe smoke test failed: "

				"register_kprobe returned %d\n", ret);

		return ret;

	}



	ret = kprobe_target(rand1);

	unregister_kprobe(&kp);



	if (preh_val == 0) {

		printk(KERN_ERR "Kprobe smoke test failed: "

				"kprobe pre_handler not called\n");

		handler_errors++;

	}



	if (posth_val == 0) {

		printk(KERN_ERR "Kprobe smoke test failed: "

				"kprobe post_handler not called\n");

		handler_errors++;

	}



	return 0;

}



static u32 j_kprobe_target(u32 value)

{

	if (value != rand1) {

		handler_errors++;

		printk(KERN_ERR "Kprobe smoke test failed: "

				"incorrect value in jprobe handler\n");

	}



	jph_val = rand1;

	jprobe_return();

	return 0;

}



static struct jprobe jp = {

	.entry		= j_kprobe_target,

	.kp.symbol_name = "kprobe_target"

};



static int test_jprobe(void)

{

	int ret;



	ret = register_jprobe(&jp);

	if (ret < 0) {

		printk(KERN_ERR "Kprobe smoke test failed: "

				"register_jprobe returned %d\n", ret);

		return ret;

	}



	ret = kprobe_target(rand1);

	unregister_jprobe(&jp);

	if (jph_val == 0) {

		printk(KERN_ERR "Kprobe smoke test failed: "

				"jprobe handler not called\n");

		handler_errors++;

	}



	return 0;

}



#ifdef CONFIG_KRETPROBES

static u32 krph_val;



static int return_handler(struct kretprobe_instance *ri, struct pt_regs *regs)

{

	unsigned long ret = regs_return_value(regs);



	if (ret != (rand1 / div_factor)) {

		handler_errors++;

		printk(KERN_ERR "Kprobe smoke test failed: "

				"incorrect value in kretprobe handler\n");

	}



	krph_val = (rand1 / div_factor);

	return 0;

}



static struct kretprobe rp = {

	.handler	= return_handler,

	.kp.symbol_name = "kprobe_target"

};



static int test_kretprobe(void)

{

	int ret;



	ret = register_kretprobe(&rp);

	if (ret < 0) {

		printk(KERN_ERR "Kprobe smoke test failed: "

				"register_kretprobe returned %d\n", ret);

		return ret;

	}



	ret = kprobe_target(rand1);

	unregister_kretprobe(&rp);

	if (krph_val == 0) {

		printk(KERN_ERR "Kprobe smoke test failed: "

				"kretprobe handler not called\n");

		handler_errors++;

	}



	return 0;

}

#endif /* CONFIG_KRETPROBES */



int init_test_probes(void)

{

	int ret;



	do {

		rand1 = random32();

	} while (rand1 <= div_factor);



	printk(KERN_INFO "Kprobe smoke test started\n");

	num_tests++;

	ret = test_kprobe();

	if (ret < 0)

		errors++;



	num_tests++;

	ret = test_jprobe();

	if (ret < 0)

		errors++;



#ifdef CONFIG_KRETPROBES

	num_tests++;

	ret = test_kretprobe();

	if (ret < 0)

		errors++;

#endif /* CONFIG_KRETPROBES */



	if (errors)

		printk(KERN_ERR "BUG: Kprobe smoke test: %d out of "

				"%d tests failed\n", errors, num_tests);

	else if (handler_errors)

		printk(KERN_ERR "BUG: Kprobe smoke test: %d error(s) "

				"running handlers\n", handler_errors);

	else

		printk(KERN_INFO "Kprobe smoke test passed successfully\n");



	return 0;

}

lib/Kconfig.debug

+12 −0
Original line number Diff line number Diff line
@@ -494,6 +494,18 @@ config RCU_TORTURE_TEST 
	  Say M if you want the RCU torture tests to build as a module.

	  Say N if you are unsure.



config KPROBES_SANITY_TEST

	bool "Kprobes sanity tests"

	depends on DEBUG_KERNEL

	depends on KPROBES

	default n

	help

	  This option provides for testing basic kprobes functionality on

	  boot. A sample kprobe, jprobe and kretprobe are inserted and

	  verified for functionality.



	  Say N if you are unsure.



config LKDTM

	tristate "Linux Kernel Dump Test Tool Module"

	depends on DEBUG_KERNEL