[PATCH v2 0/2] Add strprefix() and fix a bug with it

[Alejandro Colomar <alx@kernel.org>]

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Hi!

str_has_prefix() is based on sizes and lengths, which means it must
overload the valid length 0 to mean not found.  This is a typical
consequence of choosing to design an API around sizes and lengths, and
vanishes when moving to pointer-based similar APIs.

This patch set adds strprefix(), deprecates str_has_prefix(), and uses
strprefix() in one place to fix a bug reported by Bartosz.

We can later work on replacing the other uses of str_has_prefix(), which
might hide similar bugs.

Changes in v2
~~~~~~~~~~~~~

-  Added tests, as suggested by Andy.
-  Remove Cc tags from the commit messages.  [Andy]

Testing
~~~~~~~

The new tests added for strprefix() pass.  Below is the session I ran
for testing.  The important line is:

	[13:26:30] [PASSED] string_test_strprefix

Full session:

	$ cat .kunitconfig 
	CONFIG_KUNIT=y
	CONFIG_STRING_KUNIT_TEST=y
	$ mkdir -p ~/tmp
	$ export TMPDIR=$HOME/tmp
	$ ./tools/testing/kunit/kunit.py run "string*"
	[13:26:28] Configuring KUnit Kernel ...
	[13:26:28] Building KUnit Kernel ...
	Populating config with:
	$ make ARCH=um O=.kunit olddefconfig
	Building with:
	$ make all compile_commands.json scripts_gdb ARCH=um O=.kunit --jobs=24
	[13:26:30] Starting KUnit Kernel (1/1)...
	[13:26:30] ============================================================
	Running tests with:
	$ .kunit/linux 'kunit.filter_glob=string*' kunit.enable=1 mem=1G console=tty kunit_shutdown=halt
	[13:26:30] ============= string-stream-test (12 subtests) =============
	[13:26:30] [PASSED] string_stream_managed_init_test
	[13:26:30] [PASSED] string_stream_unmanaged_init_test
	[13:26:30] [PASSED] string_stream_managed_free_test
	[13:26:30] [PASSED] string_stream_resource_free_test
	[13:26:30] [PASSED] string_stream_line_add_test
	[13:26:30] [PASSED] string_stream_variable_length_line_test
	[13:26:30] [PASSED] string_stream_append_test
	[13:26:30] [PASSED] string_stream_append_auto_newline_test
	[13:26:30] [PASSED] string_stream_append_empty_string_test
	[13:26:30] [PASSED] string_stream_no_auto_newline_test
	[13:26:30] [PASSED] string_stream_auto_newline_test
	[13:26:30] [PASSED] string_stream_performance_test
	[13:26:30] =============== [PASSED] string-stream-test ================
	[13:26:30] =================== string (29 subtests) ===================
	[13:26:30] [PASSED] string_test_memset16
	[13:26:30] [PASSED] string_test_memset32
	[13:26:30] [PASSED] string_test_memset64
	[13:26:30] [PASSED] string_test_strlen
	[13:26:30] [PASSED] string_test_strnlen
	[13:26:30] [PASSED] string_test_strchr
	[13:26:30] [PASSED] string_test_strnchr
	[13:26:30] [PASSED] string_test_strrchr
	[13:26:30] [PASSED] string_test_strspn
	[13:26:30] [PASSED] string_test_strprefix
	[13:26:30] [PASSED] string_test_strcmp
	[13:26:30] [PASSED] string_test_strcmp_long_strings
	[13:26:30] [PASSED] string_test_strncmp
	[13:26:30] [PASSED] string_test_strncmp_long_strings
	[13:26:30] [PASSED] string_test_strcasecmp
	[13:26:30] [PASSED] string_test_strcasecmp_long_strings
	[13:26:30] [PASSED] string_test_strncasecmp
	[13:26:30] [PASSED] string_test_strncasecmp_long_strings
	[13:26:30] [PASSED] string_test_strscpy
	[13:26:30] [PASSED] string_test_strcat
	[13:26:30] [PASSED] string_test_strncat
	[13:26:30] [PASSED] string_test_strlcat
	[13:26:30] [PASSED] string_test_strtomem
	[13:26:30] [PASSED] string_test_memtostr
	[13:26:30] [PASSED] string_test_strends
	[13:26:30] [SKIPPED] string_bench_strlen (not enabled)
	[13:26:30] [SKIPPED] string_bench_strnlen (not enabled)
	[13:26:30] [SKIPPED] string_bench_strchr (not enabled)
	[13:26:30] [SKIPPED] string_bench_strrchr (not enabled)
	[13:26:30] ===================== [PASSED] string ======================
	[13:26:30] =============== string_helpers (4 subtests) ================
	[13:26:30] [PASSED] test_get_size
	[13:26:30] [PASSED] test_upper_lower
	[13:26:30] [PASSED] test_unescape
	[13:26:30] [PASSED] test_escape
	[13:26:30] ================= [PASSED] string_helpers ==================
	[13:26:30] ============================================================
	[13:26:30] Testing complete. Ran 45 tests: passed: 41, skipped: 4
	[13:26:31] Elapsed time: 2.509s total, 0.001s configuring, 2.192s building, 0.271s running


Cheers,
Alex

Alejandro Colomar (2):
  string: Add strprefix(), and deprecate str_has_prefix()
  device property: Fix fwnode_name_eq() for empty node names

 drivers/base/property.c  |  5 +----
 include/linux/string.h   | 19 ++++++++++++++++++-
 lib/tests/string_kunit.c |  9 +++++++++
 3 files changed, 28 insertions(+), 5 deletions(-)

Range-diff against v1:
1:  9c81f6f62fd0 ! 1:  d3b325ecefd1 string: Add strprefix(), and deprecate str_has_prefix()
    @@ Commit message
         We'll slowly migrate existing code from str_has_prefix() to strprefix().
     
         Reported-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
    -    Cc: Andreas Schwab <schwab@linux-m68k.org>
    -    Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
         Cc: Andy Shevchenko <andy@kernel.org>
    -    Cc: Bartosz Golaszewski <brgl@kernel.org>
    -    Cc: Daniel Scally <djrscally@gmail.com>
    -    Cc: Danilo Krummrich <dakr@kernel.org>
    -    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    -    Cc: Hans Verkuil <hverkuil-cisco@xs4all.nl>
    -    Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
    -    Cc: Joe Perches <joe@perches.com>
    -    Cc: Johan Hovold <johan@kernel.org>
    -    Cc: Kees Cook <kees@kernel.org>
    -    Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
    -    Cc: Len Brown <lenb@kernel.org>
    -    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    -    Cc: Linus Walleij <linusw@kernel.org>
    -    Cc: Namhyung Kim <namhyung@kernel.org>
    -    Cc: "Rafael J. Wysocki" <rafael@kernel.org>
    -    Cc: Rob Herring <robh@kernel.org>
    -    Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
    -    Cc: Saravana Kannan <saravanak@kernel.org>
    -    Cc: Steven Rostedt <rostedt@goodmis.org>
    -    Cc: Tom Zanussi <zanussi@kernel.org
    -    Cc: linux-acpi@vger.kernel.org
    -    Cc: driver-core@lists.linux.dev
    -    Cc: linux-kernel@vger.kernel.org
    -    Cc: linux-hardening@vger.kernel.org
    -    Cc: devicetree@vger.kernel.org
    -    Cc: linux-gpio@vger.kernel.org
         Signed-off-by: Alejandro Colomar <alx@kernel.org>
     
      ## include/linux/string.h ##
    @@ include/linux/string.h: void memcpy_and_pad(void *dest, size_t dest_len, const v
       *
       * Returns:
       * * strlen(@prefix) if @str starts with @prefix
    +
    + ## lib/tests/string_kunit.c ##
    +@@ lib/tests/string_kunit.c: static void string_test_strspn(struct kunit *test)
    + 	}
    + }
    + 
    ++static void string_test_strprefix(struct kunit *test)
    ++{
    ++	KUNIT_ASSERT_EQ(test, 0, strcmp(strprefix("foobar", "foo"), "bar"));
    ++	KUNIT_ASSERT_EQ(test, 0, strcmp(strprefix("foobar", ""), "foobar"));
    ++	KUNIT_ASSERT_EQ(test, 0, strcmp(strprefix("foobar", "foobar"), ""));
    ++	KUNIT_ASSERT_NULL(test, strprefix("foobar", "bar"));
    ++}
    ++
    + static char strcmp_buffer1[STRCMP_LARGE_BUF_LEN];
    + static char strcmp_buffer2[STRCMP_LARGE_BUF_LEN];
    + 
    +@@ lib/tests/string_kunit.c: static struct kunit_case string_test_cases[] = {
    + 	KUNIT_CASE(string_test_strnchr),
    + 	KUNIT_CASE(string_test_strrchr),
    + 	KUNIT_CASE(string_test_strspn),
    ++	KUNIT_CASE(string_test_strprefix),
    + 	KUNIT_CASE(string_test_strcmp),
    + 	KUNIT_CASE(string_test_strcmp_long_strings),
    + 	KUNIT_CASE(string_test_strncmp),
2:  37eafcd682b0 ! 2:  ac9728afa027 device property: Fix fwnode_name_eq() for empty node names
    @@ Commit message
     
         Fixes: a9c8c738066b7 ("device property: Add fwnode_name_eq()")
         Reported-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
    -    Cc: Andreas Schwab <schwab@linux-m68k.org>
    -    Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
         Cc: Andy Shevchenko <andy@kernel.org>
    -    Cc: Bartosz Golaszewski <brgl@kernel.org>
    -    Cc: Daniel Scally <djrscally@gmail.com>
    -    Cc: Danilo Krummrich <dakr@kernel.org>
    -    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    -    Cc: Hans Verkuil <hverkuil-cisco@xs4all.nl>
    -    Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
    -    Cc: Joe Perches <joe@perches.com>
    -    Cc: Johan Hovold <johan@kernel.org>
    -    Cc: Kees Cook <kees@kernel.org>
    -    Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
    -    Cc: Len Brown <lenb@kernel.org>
    -    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    -    Cc: Linus Walleij <linusw@kernel.org>
    -    Cc: Namhyung Kim <namhyung@kernel.org>
    -    Cc: "Rafael J. Wysocki" <rafael@kernel.org>
    -    Cc: Rob Herring <robh@kernel.org>
    -    Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
    -    Cc: Saravana Kannan <saravanak@kernel.org>
    -    Cc: Steven Rostedt <rostedt@goodmis.org>
    -    Cc: Tom Zanussi <zanussi@kernel.org
    -    Cc: linux-acpi@vger.kernel.org
    -    Cc: driver-core@lists.linux.dev
    -    Cc: linux-kernel@vger.kernel.org
    -    Cc: linux-hardening@vger.kernel.org
    -    Cc: devicetree@vger.kernel.org
    -    Cc: linux-gpio@vger.kernel.org
         Signed-off-by: Alejandro Colomar <alx@kernel.org>
     
      ## drivers/base/property.c ##
-- 
2.55.0


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