lib/test_fprobe.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * test_fprobe.c - simple sanity test for fprobe
 */

#include <linux/kernel.h>
#include <linux/fprobe.h>
#include <linux/random.h>
#include <kunit/test.h>

#define div_factor 3

static struct kunit *current_test;

static u32 rand1, entry_val, exit_val;

/* Use indirect calls to avoid inlining the target functions */
static u32 (*target)(u32 value);
static u32 (*target2)(u32 value);
static unsigned long target_ip;
static unsigned long target2_ip;

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

static noinline u32 fprobe_selftest_target2(u32 value)
{
	return (value / div_factor) + 1;
}

static notrace void fp_entry_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs)
{
	KUNIT_EXPECT_FALSE(current_test, preemptible());
	/* This can be called on the fprobe_selftest_target and the fprobe_selftest_target2 */
	if (ip != target_ip)
		KUNIT_EXPECT_EQ(current_test, ip, target2_ip);
	entry_val = (rand1 / div_factor);
}

static notrace void fp_exit_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs)
{
	unsigned long ret = regs_return_value(regs);

	KUNIT_EXPECT_FALSE(current_test, preemptible());
	if (ip != target_ip) {
		KUNIT_EXPECT_EQ(current_test, ip, target2_ip);
		KUNIT_EXPECT_EQ(current_test, ret, (rand1 / div_factor) + 1);
	} else
		KUNIT_EXPECT_EQ(current_test, ret, (rand1 / div_factor));
	KUNIT_EXPECT_EQ(current_test, entry_val, (rand1 / div_factor));
	exit_val = entry_val + div_factor;
}

/* Test entry only (no rethook) */
static void test_fprobe_entry(struct kunit *test)
{
	struct fprobe fp_entry = {
		.entry_handler = fp_entry_handler,
	};

	current_test = test;

	/* Before register, unregister should be failed. */
	KUNIT_EXPECT_NE(test, 0, unregister_fprobe(&fp_entry));
	KUNIT_EXPECT_EQ(test, 0, register_fprobe(&fp_entry, "fprobe_selftest_target*", NULL));

	entry_val = 0;
	exit_val = 0;
	target(rand1);
	KUNIT_EXPECT_NE(test, 0, entry_val);
	KUNIT_EXPECT_EQ(test, 0, exit_val);

	entry_val = 0;
	exit_val = 0;
	target2(rand1);
	KUNIT_EXPECT_NE(test, 0, entry_val);
	KUNIT_EXPECT_EQ(test, 0, exit_val);

	KUNIT_EXPECT_EQ(test, 0, unregister_fprobe(&fp_entry));
}

static void test_fprobe(struct kunit *test)
{
	struct fprobe fp = {
		.entry_handler = fp_entry_handler,
		.exit_handler = fp_exit_handler,
	};

	current_test = test;
	KUNIT_EXPECT_EQ(test, 0, register_fprobe(&fp, "fprobe_selftest_target*", NULL));

	entry_val = 0;
	exit_val = 0;
	target(rand1);
	KUNIT_EXPECT_NE(test, 0, entry_val);
	KUNIT_EXPECT_EQ(test, entry_val + div_factor, exit_val);

	entry_val = 0;
	exit_val = 0;
	target2(rand1);
	KUNIT_EXPECT_NE(test, 0, entry_val);
	KUNIT_EXPECT_EQ(test, entry_val + div_factor, exit_val);

	KUNIT_EXPECT_EQ(test, 0, unregister_fprobe(&fp));
}

static void test_fprobe_syms(struct kunit *test)
{
	static const char *syms[] = {"fprobe_selftest_target", "fprobe_selftest_target2"};
	struct fprobe fp = {
		.entry_handler = fp_entry_handler,
		.exit_handler = fp_exit_handler,
	};

	current_test = test;
	KUNIT_EXPECT_EQ(test, 0, register_fprobe_syms(&fp, syms, 2));

	entry_val = 0;
	exit_val = 0;
	target(rand1);
	KUNIT_EXPECT_NE(test, 0, entry_val);
	KUNIT_EXPECT_EQ(test, entry_val + div_factor, exit_val);

	entry_val = 0;
	exit_val = 0;
	target2(rand1);
	KUNIT_EXPECT_NE(test, 0, entry_val);
	KUNIT_EXPECT_EQ(test, entry_val + div_factor, exit_val);

	KUNIT_EXPECT_EQ(test, 0, unregister_fprobe(&fp));
}

static unsigned long get_ftrace_location(void *func)
{
	unsigned long size, addr = (unsigned long)func;

	if (!kallsyms_lookup_size_offset(addr, &size, NULL) || !size)
		return 0;

	return ftrace_location_range(addr, addr + size - 1);
}

static int fprobe_test_init(struct kunit *test)
{
	do {
		rand1 = prandom_u32();
	} while (rand1 <= div_factor);

	target = fprobe_selftest_target;
	target2 = fprobe_selftest_target2;
	target_ip = get_ftrace_location(target);
	target2_ip = get_ftrace_location(target2);

	return 0;
}

static struct kunit_case fprobe_testcases[] = {
	KUNIT_CASE(test_fprobe_entry),
	KUNIT_CASE(test_fprobe),
	KUNIT_CASE(test_fprobe_syms),
	{}
};

static struct kunit_suite fprobe_test_suite = {
	.name = "fprobe_test",
	.init = fprobe_test_init,
	.test_cases = fprobe_testcases,
};

kunit_test_suites(&fprobe_test_suite);

MODULE_LICENSE("GPL");