selftests/bpf: Add test cases for bpf_strncmp()

// SPDX-License-Identifier: GPL-2.0

/* Copyright (C) 2021. Huawei Technologies Co., Ltd */

#include <test_progs.h>

#include "strncmp_test.skel.h"

static int trigger_strncmp(const struct strncmp_test *skel)

{

	int cmp;

	usleep(1);

	cmp = skel->bss->cmp_ret;

	if (cmp > 0)

		return 1;

	if (cmp < 0)

		return -1;

	return 0;

}

/*

 * Compare str and target after making str[i] != target[i].

 * When exp is -1, make str[i] < target[i] and delta = -1.

 */

static void strncmp_full_str_cmp(struct strncmp_test *skel, const char *name,

				 int exp)

{

	size_t nr = sizeof(skel->bss->str);

	char *str = skel->bss->str;

	int delta = exp;

	int got;

	size_t i;

	memcpy(str, skel->rodata->target, nr);

	for (i = 0; i < nr - 1; i++) {

		str[i] += delta;

		got = trigger_strncmp(skel);

		ASSERT_EQ(got, exp, name);

		str[i] -= delta;

	}

}

static void test_strncmp_ret(void)

{

	struct strncmp_test *skel;

	struct bpf_program *prog;

	int err, got;

	skel = strncmp_test__open();

	if (!ASSERT_OK_PTR(skel, "strncmp_test open"))

		return;

	bpf_object__for_each_program(prog, skel->obj)

		bpf_program__set_autoload(prog, false);

	bpf_program__set_autoload(skel->progs.do_strncmp, true);

	err = strncmp_test__load(skel);

	if (!ASSERT_EQ(err, 0, "strncmp_test load"))

		goto out;

	err = strncmp_test__attach(skel);

	if (!ASSERT_EQ(err, 0, "strncmp_test attach"))

		goto out;

	skel->bss->target_pid = getpid();

	/* Empty str */

	skel->bss->str[0] = '\0';

	got = trigger_strncmp(skel);

	ASSERT_EQ(got, -1, "strncmp: empty str");

	/* Same string */

	memcpy(skel->bss->str, skel->rodata->target, sizeof(skel->bss->str));

	got = trigger_strncmp(skel);

	ASSERT_EQ(got, 0, "strncmp: same str");

	/* Not-null-termainted string  */

	memcpy(skel->bss->str, skel->rodata->target, sizeof(skel->bss->str));

	skel->bss->str[sizeof(skel->bss->str) - 1] = 'A';

	got = trigger_strncmp(skel);

	ASSERT_EQ(got, 1, "strncmp: not-null-term str");

	strncmp_full_str_cmp(skel, "strncmp: less than", -1);

	strncmp_full_str_cmp(skel, "strncmp: greater than", 1);

out:

	strncmp_test__destroy(skel);

}

static void test_strncmp_bad_not_const_str_size(void)

{

	struct strncmp_test *skel;

	struct bpf_program *prog;

	int err;

	skel = strncmp_test__open();

	if (!ASSERT_OK_PTR(skel, "strncmp_test open"))

		return;

	bpf_object__for_each_program(prog, skel->obj)

		bpf_program__set_autoload(prog, false);

	bpf_program__set_autoload(skel->progs.strncmp_bad_not_const_str_size,

				  true);

	err = strncmp_test__load(skel);

	ASSERT_ERR(err, "strncmp_test load bad_not_const_str_size");

	strncmp_test__destroy(skel);

}

static void test_strncmp_bad_writable_target(void)

{

	struct strncmp_test *skel;

	struct bpf_program *prog;

	int err;

	skel = strncmp_test__open();

	if (!ASSERT_OK_PTR(skel, "strncmp_test open"))

		return;

	bpf_object__for_each_program(prog, skel->obj)

		bpf_program__set_autoload(prog, false);

	bpf_program__set_autoload(skel->progs.strncmp_bad_writable_target,

				  true);

	err = strncmp_test__load(skel);

	ASSERT_ERR(err, "strncmp_test load bad_writable_target");

	strncmp_test__destroy(skel);

}

static void test_strncmp_bad_not_null_term_target(void)

{

	struct strncmp_test *skel;

	struct bpf_program *prog;

	int err;

	skel = strncmp_test__open();

	if (!ASSERT_OK_PTR(skel, "strncmp_test open"))

		return;

	bpf_object__for_each_program(prog, skel->obj)

		bpf_program__set_autoload(prog, false);

	bpf_program__set_autoload(skel->progs.strncmp_bad_not_null_term_target,

				  true);

	err = strncmp_test__load(skel);

	ASSERT_ERR(err, "strncmp_test load bad_not_null_term_target");

	strncmp_test__destroy(skel);

}

void test_test_strncmp(void)

{

	if (test__start_subtest("strncmp_ret"))

		test_strncmp_ret();

	if (test__start_subtest("strncmp_bad_not_const_str_size"))

		test_strncmp_bad_not_const_str_size();

	if (test__start_subtest("strncmp_bad_writable_target"))

		test_strncmp_bad_writable_target();

	if (test__start_subtest("strncmp_bad_not_null_term_target"))

		test_strncmp_bad_not_null_term_target();

}

// SPDX-License-Identifier: GPL-2.0

/* Copyright (C) 2021. Huawei Technologies Co., Ltd */

#include <stdbool.h>

#include <linux/types.h>

#include <linux/bpf.h>

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>

#define STRNCMP_STR_SZ 8

const char target[STRNCMP_STR_SZ] = "EEEEEEE";

char str[STRNCMP_STR_SZ];

int cmp_ret = 0;

int target_pid = 0;

const char no_str_target[STRNCMP_STR_SZ] = "12345678";

char writable_target[STRNCMP_STR_SZ];

unsigned int no_const_str_size = STRNCMP_STR_SZ;

char _license[] SEC("license") = "GPL";

SEC("tp/syscalls/sys_enter_nanosleep")

int do_strncmp(void *ctx)

{

	if ((bpf_get_current_pid_tgid() >> 32) != target_pid)

		return 0;

	cmp_ret = bpf_strncmp(str, STRNCMP_STR_SZ, target);

	return 0;

}

SEC("tp/syscalls/sys_enter_nanosleep")

int strncmp_bad_not_const_str_size(void *ctx)

{

	/* The value of string size is not const, so will fail */

	cmp_ret = bpf_strncmp(str, no_const_str_size, target);

	return 0;

}

SEC("tp/syscalls/sys_enter_nanosleep")

int strncmp_bad_writable_target(void *ctx)

{

	/* Compared target is not read-only, so will fail */

	cmp_ret = bpf_strncmp(str, STRNCMP_STR_SZ, writable_target);

	return 0;

}

SEC("tp/syscalls/sys_enter_nanosleep")

int strncmp_bad_not_null_term_target(void *ctx)

{

	/* Compared target is not null-terminated, so will fail */

	cmp_ret = bpf_strncmp(str, STRNCMP_STR_SZ, no_str_target);

	return 0;

}