Re: [PATCH v10 12/12] fprobe: Add a selftest for fprobe

[Masami Hiramatsu <mhiramat@kernel.org>]

Hi,

On Tue,  8 Mar 2022 20:10:48 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> Add a KUnit based selftest for fprobe interface.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> ---
>  Changes in v9:
>   - Rename fprobe_target* to fprobe_selftest_target*.
>   - Find the correct expected ip by ftrace_location_range().
>   - Since the ftrace_location_range() is not exposed to module, make
>     this test only for embedded.
>   - Add entry only test.
>   - Reset the fprobe structure before reuse it.
> ---
>  lib/Kconfig.debug |   12 ++++
>  lib/Makefile      |    2 +
>  lib/test_fprobe.c |  174 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 188 insertions(+)
>  create mode 100644 lib/test_fprobe.c
> 
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 14b89aa37c5c..ffc469a12afc 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -2100,6 +2100,18 @@ config KPROBES_SANITY_TEST
>  
>  	  Say N if you are unsure.
>  
> +config FPROBE_SANITY_TEST
> +	bool "Self test for fprobe"
> +	depends on DEBUG_KERNEL
> +	depends on FPROBE
> +	depends on KUNIT

Hmm, this caused a build error with allmodconfig because KUNIT=m but FPROBE_SANITY_TEST=y.
Let me fix this issue.

Thank you,

> +	help
> +	  This option will enable testing the fprobe when the system boot.
> +	  A series of tests are made to verify that the fprobe is functioning
> +	  properly.
> +
> +	  Say N if you are unsure.
> +
>  config BACKTRACE_SELF_TEST
>  	tristate "Self test for the backtrace code"
>  	depends on DEBUG_KERNEL
> diff --git a/lib/Makefile b/lib/Makefile
> index 300f569c626b..154008764b16 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -103,6 +103,8 @@ obj-$(CONFIG_TEST_HMM) += test_hmm.o
>  obj-$(CONFIG_TEST_FREE_PAGES) += test_free_pages.o
>  obj-$(CONFIG_KPROBES_SANITY_TEST) += test_kprobes.o
>  obj-$(CONFIG_TEST_REF_TRACKER) += test_ref_tracker.o
> +CFLAGS_test_fprobe.o += $(CC_FLAGS_FTRACE)
> +obj-$(CONFIG_FPROBE_SANITY_TEST) += test_fprobe.o
>  #
>  # CFLAGS for compiling floating point code inside the kernel. x86/Makefile turns
>  # off the generation of FPU/SSE* instructions for kernel proper but FPU_FLAGS
> diff --git a/lib/test_fprobe.c b/lib/test_fprobe.c
> new file mode 100644
> index 000000000000..ed70637a2ffa
> --- /dev/null
> +++ b/lib/test_fprobe.c
> @@ -0,0 +1,174 @@
> +// 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");
> 


-- 
Masami Hiramatsu <mhiramat@kernel.org>