test_kprobes.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * test_kprobes.c - simple sanity test for *probes
 *
 * Copyright IBM Corp. 2008
 */

#define pr_fmt(fmt) "Kprobe smoke test: " fmt

#include <linux/kernel.h>
#include <linux/kprobes.h>
#include <linux/random.h>

#define div_factor 3

static u32 rand1, preh_val, posth_val;
static int errors, handler_errors, num_tests;
static u32 (*target)(u32 value);
static u32 (*target2)(u32 value);

static noinline u32 kprobe_target(u32 value)
{
	return (value / div_factor);
}

static int kp_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
	if (preemptible()) {
		handler_errors++;
		pr_err("pre-handler is preemptible\n");
	}
	preh_val = (rand1 / div_factor);
	return 0;
}

static void kp_post_handler(struct kprobe *p, struct pt_regs *regs,
		unsigned long flags)
{
	if (preemptible()) {
		handler_errors++;
		pr_err("post-handler is preemptible\n");
	}
	if (preh_val != (rand1 / div_factor)) {
		handler_errors++;
		pr_err("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) {
		pr_err("register_kprobe returned %d\n", ret);
		return ret;
	}

	ret = target(rand1);
	unregister_kprobe(&kp);

	if (preh_val == 0) {
		pr_err("kprobe pre_handler not called\n");
		handler_errors++;
	}

	if (posth_val == 0) {
		pr_err("kprobe post_handler not called\n");
		handler_errors++;
	}

	return 0;
}

static noinline u32 kprobe_target2(u32 value)
{
	return (value / div_factor) + 1;
}

static int kp_pre_handler2(struct kprobe *p, struct pt_regs *regs)
{
	preh_val = (rand1 / div_factor) + 1;
	return 0;
}

static void kp_post_handler2(struct kprobe *p, struct pt_regs *regs,
		unsigned long flags)
{
	if (preh_val != (rand1 / div_factor) + 1) {
		handler_errors++;
		pr_err("incorrect value in post_handler2\n");
	}
	posth_val = preh_val + div_factor;
}

static struct kprobe kp2 = {
	.symbol_name = "kprobe_target2",
	.pre_handler = kp_pre_handler2,
	.post_handler = kp_post_handler2
};

static int test_kprobes(void)
{
	int ret;
	struct kprobe *kps[2] = {&kp, &kp2};

	/* addr and flags should be cleard for reusing kprobe. */
	kp.addr = NULL;
	kp.flags = 0;
	ret = register_kprobes(kps, 2);
	if (ret < 0) {
		pr_err("register_kprobes returned %d\n", ret);
		return ret;
	}

	preh_val = 0;
	posth_val = 0;
	ret = target(rand1);

	if (preh_val == 0) {
		pr_err("kprobe pre_handler not called\n");
		handler_errors++;
	}

	if (posth_val == 0) {
		pr_err("kprobe post_handler not called\n");
		handler_errors++;
	}

	preh_val = 0;
	posth_val = 0;
	ret = target2(rand1);

	if (preh_val == 0) {
		pr_err("kprobe pre_handler2 not called\n");
		handler_errors++;
	}

	if (posth_val == 0) {
		pr_err("kprobe post_handler2 not called\n");
		handler_errors++;
	}

	unregister_kprobes(kps, 2);
	return 0;

}

#ifdef CONFIG_KRETPROBES
static u32 krph_val;

static int entry_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
{
	if (preemptible()) {
		handler_errors++;
		pr_err("kretprobe entry handler is preemptible\n");
	}
	krph_val = (rand1 / div_factor);
	return 0;
}

static int return_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
{
	unsigned long ret = regs_return_value(regs);

	if (preemptible()) {
		handler_errors++;
		pr_err("kretprobe return handler is preemptible\n");
	}
	if (ret != (rand1 / div_factor)) {
		handler_errors++;
		pr_err("incorrect value in kretprobe handler\n");
	}
	if (krph_val == 0) {
		handler_errors++;
		pr_err("call to kretprobe entry handler failed\n");
	}

	krph_val = rand1;
	return 0;
}

static struct kretprobe rp = {
	.handler	= return_handler,
	.entry_handler  = entry_handler,
	.kp.symbol_name = "kprobe_target"
};

static int test_kretprobe(void)
{
	int ret;

	ret = register_kretprobe(&rp);
	if (ret < 0) {
		pr_err("register_kretprobe returned %d\n", ret);
		return ret;
	}

	ret = target(rand1);
	unregister_kretprobe(&rp);
	if (krph_val != rand1) {
		pr_err("kretprobe handler not called\n");
		handler_errors++;
	}

	return 0;
}

static int return_handler2(struct kretprobe_instance *ri, struct pt_regs *regs)
{
	unsigned long ret = regs_return_value(regs);

	if (ret != (rand1 / div_factor) + 1) {
		handler_errors++;
		pr_err("incorrect value in kretprobe handler2\n");
	}
	if (krph_val == 0) {
		handler_errors++;
		pr_err("call to kretprobe entry handler failed\n");
	}

	krph_val = rand1;
	return 0;
}

static struct kretprobe rp2 = {
	.handler	= return_handler2,
	.entry_handler  = entry_handler,
	.kp.symbol_name = "kprobe_target2"
};

static int test_kretprobes(void)
{
	int ret;
	struct kretprobe *rps[2] = {&rp, &rp2};

	/* addr and flags should be cleard for reusing kprobe. */
	rp.kp.addr = NULL;
	rp.kp.flags = 0;
	ret = register_kretprobes(rps, 2);
	if (ret < 0) {
		pr_err("register_kretprobe returned %d\n", ret);
		return ret;
	}

	krph_val = 0;
	ret = target(rand1);
	if (krph_val != rand1) {
		pr_err("kretprobe handler not called\n");
		handler_errors++;
	}

	krph_val = 0;
	ret = target2(rand1);
	if (krph_val != rand1) {
		pr_err("kretprobe handler2 not called\n");
		handler_errors++;
	}
	unregister_kretprobes(rps, 2);
	return 0;
}
#endif /* CONFIG_KRETPROBES */

int init_test_probes(void)
{
	int ret;

	target = kprobe_target;
	target2 = kprobe_target2;

	do {
		rand1 = prandom_u32();
	} while (rand1 <= div_factor);

	pr_info("started\n");
	num_tests++;
	ret = test_kprobe();
	if (ret < 0)
		errors++;

	num_tests++;
	ret = test_kprobes();
	if (ret < 0)
		errors++;

#ifdef CONFIG_KRETPROBES
	num_tests++;
	ret = test_kretprobe();
	if (ret < 0)
		errors++;

	num_tests++;
	ret = test_kretprobes();
	if (ret < 0)
		errors++;
#endif /* CONFIG_KRETPROBES */

	if (errors)
		pr_err("BUG: %d out of %d tests failed\n", errors, num_tests);
	else if (handler_errors)
		pr_err("BUG: %d error(s) running handlers\n", handler_errors);
	else
		pr_info("passed successfully\n");

	return 0;
}