Re: [PATCH v5 1/3] printf: convert self-test to KUnit

Petr Mladek
2025-03-06T12:25:07Z

On Fri 2025-02-21 15:34:30, Tamir Duberstein wrote:
> Convert the printf() self-test to a KUnit test.
>
> In the interest of keeping the patch reasonably-sized this doesn't
> refactor the tests into proper parameterized tests - it's all one big
> test case.
>
> Signed-off-by: Tamir Duberstein <tamird@gmail.com>
> ---
> Documentation/core-api/printk-formats.rst | 4 +-
> MAINTAINERS | 2 +-
> lib/Kconfig.debug | 12 +-
> lib/Makefile | 1 -
> lib/tests/Makefile | 1 +
> lib/{test_printf.c => tests/printf_kunit.c} | 188 +++++++++++++++-------------
> tools/testing/selftests/lib/config | 1 -
> tools/testing/selftests/lib/printf.sh | 4 -
> 8 files changed, 117 insertions(+), 96 deletions(-)
>
> diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst
> index ecccc0473da9..4bdc394e86af 100644
> --- a/Documentation/core-api/printk-formats.rst
> +++ b/Documentation/core-api/printk-formats.rst
> @@ -661,7 +661,7 @@ Do *not* use it from C.
> Thanks
> ======
>
> -If you add other %p extensions, please extend <lib/test_printf.c> with
> -one or more test cases, if at all feasible.
> +If you add other %p extensions, please extend <lib/tests/printf_kunit.c>
> +with one or more test cases, if at all feasible.
>
> Thank you for your cooperation and attention.
> diff --git a/MAINTAINERS b/MAINTAINERS
> index f076360ce3c6..b051ccf6b276 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -25510,8 +25510,8 @@ R: Sergey Senozhatsky <senozhatsky@chromium.org>
> S: Maintained
> T: git git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux.git
> F: Documentation/core-api/printk-formats.rst
> -F: lib/test_printf.c
> F: lib/test_scanf.c
> +F: lib/tests/printf_kunit.c
> F: lib/vsprintf.c
>
> VT1211 HARDWARE MONITOR DRIVER
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 7ddbfdacf895..d2b15f633227 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -2436,6 +2436,15 @@ config ASYNC_RAID6_TEST
> config TEST_HEXDUMP
> tristate "Test functions located in the hexdump module at runtime"
>
> +config PRINTF_KUNIT_TEST
> + tristate "KUnit test printf() family of functions at runtime" if !KUNIT_ALL_TESTS
> + depends on KUNIT
> + default KUNIT_ALL_TESTS
> + help
> + Enable this option to test the printf functions at runtime.
> +
> + If unsure, say N.
> +
> config STRING_KUNIT_TEST
> tristate "KUnit test string functions at runtime" if !KUNIT_ALL_TESTS
> depends on KUNIT
> @@ -2449,9 +2458,6 @@ config STRING_HELPERS_KUNIT_TEST
> config TEST_KSTRTOX
> tristate "Test kstrto*() family of functions at runtime"
>
> -config TEST_PRINTF
> - tristate "Test printf() family of functions at runtime"
> -
> config TEST_SCANF
> tristate "Test scanf() family of functions at runtime"
>
> diff --git a/lib/Makefile b/lib/Makefile
> index 961aef91d493..f31e6a3100ba 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -77,7 +77,6 @@ obj-$(CONFIG_TEST_RHASHTABLE) += test_rhashtable.o
> obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_keys.o
> obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_key_base.o
> obj-$(CONFIG_TEST_DYNAMIC_DEBUG) += test_dynamic_debug.o
> -obj-$(CONFIG_TEST_PRINTF) += test_printf.o
> obj-$(CONFIG_TEST_SCANF) += test_scanf.o
>
> obj-$(CONFIG_TEST_BITMAP) += test_bitmap.o
> diff --git a/lib/tests/Makefile b/lib/tests/Makefile
> index 8961fbcff7a4..183c6a838a5d 100644
> --- a/lib/tests/Makefile
> +++ b/lib/tests/Makefile
> @@ -30,6 +30,7 @@ obj-$(CONFIG_LINEAR_RANGES_TEST) += test_linear_ranges.o
> obj-$(CONFIG_MEMCPY_KUNIT_TEST) += memcpy_kunit.o
> CFLAGS_overflow_kunit.o = $(call cc-disable-warning, tautological-constant-out-of-range-compare)
> obj-$(CONFIG_OVERFLOW_KUNIT_TEST) += overflow_kunit.o
> +obj-$(CONFIG_PRINTF_KUNIT_TEST) += printf_kunit.o
> obj-$(CONFIG_SIPHASH_KUNIT_TEST) += siphash_kunit.o
> obj-$(CONFIG_SLUB_KUNIT_TEST) += slub_kunit.o
> obj-$(CONFIG_TEST_SORT) += test_sort.o
> diff --git a/lib/test_printf.c b/lib/tests/printf_kunit.c
> similarity index 87%
> rename from lib/test_printf.c
> rename to lib/tests/printf_kunit.c
> index 59dbe4f9a4cb..287bbfb61148 100644
> --- a/lib/test_printf.c
> +++ b/lib/tests/printf_kunit.c
> @@ -3,9 +3,7 @@
> * Test cases for printf facility.
> */
>
> -#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> -
> -#include <linux/init.h>
> +#include <kunit/test.h>
> #include <linux/kernel.h>
> #include <linux/module.h>
> #include <linux/printk.h>
> @@ -25,8 +23,6 @@
>
> #include <linux/property.h>
>
> -#include "../tools/testing/selftests/kselftest_module.h"
> -
> #define BUF_SIZE 256
> #define PAD_SIZE 16
> #define FILL_CHAR '$'
> @@ -37,12 +33,17 @@
> block \
> __diag_pop();
>
> -KSTM_MODULE_GLOBALS();
> +static unsigned int total_tests;
> +
> +static char *test_buffer;
> +static char *alloced_buffer;
> +
> +static struct kunit *kunittest;
>
> -static char *test_buffer __initdata;
> -static char *alloced_buffer __initdata;
> +#define tc_fail(fmt, ...) \
> + KUNIT_FAIL(kunittest, fmt, ##__VA_ARGS__)
>
> -static int __printf(4, 0) __init
> +static void __printf(4, 0)
> do_test(int bufsize, const char *expect, int elen,
> const char *fmt, va_list ap)
> {
> @@ -57,52 +58,50 @@ do_test(int bufsize, const char *expect, int elen,
> va_end(aq);
>
> if (ret != elen) {
> - pr_warn("vsnprintf(buf, %d, \"%s\", ...) returned %d, expected %d\n",
> + tc_fail("vsnprintf(buf, %d, \"%s\", ...) returned %d, expected %d",

1. It looks a bit strange that the 1st patch replaces pr_warn() with
tc_fail() which hides KUNIT_FAIL().

And the 2nd patch replaces tc_fail() with KUNIT_FAIL().

It looks like a non-necessary churn.

It would be better to avoid the temporary "tc_fail" and swith to
KUNIT_FAIL() already in this patch.

I did not find any comment about this in the earier versions of the
patchset.

Is it just a result of the evolution of the patchset or
is there any motivation for this?

2. What was the motivation to remove the trailing '\n', please?

It actually makes a difference from the printk() POV. Messages without
the trailing '\n' are _not_ flushed to the console until another
message is added. The reason is that they might still be appended
by pr_cont(). And printk() emits only complete lines to the
console.

In general, messages should include the trailing '\n' unless the
code wants to append something later or the trailing '\n' is
added by another layer of the code. It does not seem to be this case.

> bufsize, fmt, ret, elen);
> - return 1;
> + return;
> }

[...]

> @@ -842,13 +836,15 @@ test_pointer(void)
> fourcc_pointer();
> }
>
> -static void __init selftest(void)
> +static void printf_test(struct kunit *test)
> {
> alloced_buffer = kmalloc(BUF_SIZE + 2*PAD_SIZE, GFP_KERNEL);
> if (!alloced_buffer)
> return;

I would use here:

KUNIT_ASSERT_NOT_NULL(test, alloced_buffer);

And move the same change for the other kmalloc() location from
the 2nd patch.

> test_buffer = alloced_buffer + PAD_SIZE;
>
> + kunittest = test;
> +
> test_basic();
> test_number();
> test_string();

Otherwise, it looks good to me.

Best Regards,
Petr