From dff3b1f5ec6d15c2e25dd24c97da1a05d4d1b568 Mon Sep 17 00:00:00 2001 From: "Yo-Jung (Leo) Lin" <0xff07@gmail.com> Date: Tue, 30 Apr 2024 00:50:47 +0800 Subject: Documentation: kselftest: fix codeblock Add extra colon to mark command in the next paragraph as codeblock Signed-off-by: Yo-Jung (Leo) Lin <0xff07@gmail.com> Signed-off-by: Shuah Khan --- Documentation/dev-tools/kselftest.rst | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'Documentation/dev-tools') diff --git a/Documentation/dev-tools/kselftest.rst b/Documentation/dev-tools/kselftest.rst index ff10dc6eef5d..dcf634e411bd 100644 --- a/Documentation/dev-tools/kselftest.rst +++ b/Documentation/dev-tools/kselftest.rst @@ -183,7 +183,7 @@ expected time it takes to run a test. If you have control over the systems which will run the tests you can configure a test runner on those systems to use a greater or lower timeout on the command line as with the `-o` or the `--override-timeout` argument. For example to use 165 seconds instead -one would use: +one would use:: $ ./run_kselftest.sh --override-timeout 165 -- cgit v1.2.3 From 31f605a308e627f06e4e6ab77254473f1c90f0bf Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Thu, 2 May 2024 16:12:17 +0200 Subject: kcsan, compiler_types: Introduce __data_racy type qualifier Based on the discussion at [1], it would be helpful to mark certain variables as explicitly "data racy", which would result in KCSAN not reporting data races involving any accesses on such variables. To do that, introduce the __data_racy type qualifier: struct foo { ... int __data_racy bar; ... }; In KCSAN-kernels, __data_racy turns into volatile, which KCSAN already treats specially by considering them "marked". In non-KCSAN kernels the type qualifier turns into no-op. The generated code between KCSAN-instrumented kernels and non-KCSAN kernels is already huge (inserted calls into runtime for every memory access), so the extra generated code (if any) due to volatile for few such __data_racy variables are unlikely to have measurable impact on performance. Link: https://lore.kernel.org/all/CAHk-=wi3iondeh_9V2g3Qz5oHTRjLsOpoy83hb58MVh=nRZe0A@mail.gmail.com/ [1] Suggested-by: Linus Torvalds Signed-off-by: Marco Elver Cc: Paul E. McKenney Cc: Tetsuo Handa Signed-off-by: Paul E. McKenney --- Documentation/dev-tools/kcsan.rst | 10 ++++++++++ include/linux/compiler_types.h | 7 +++++++ kernel/kcsan/kcsan_test.c | 17 +++++++++++++++++ 3 files changed, 34 insertions(+) (limited to 'Documentation/dev-tools') diff --git a/Documentation/dev-tools/kcsan.rst b/Documentation/dev-tools/kcsan.rst index 94b6802ab0ab..02143f060b22 100644 --- a/Documentation/dev-tools/kcsan.rst +++ b/Documentation/dev-tools/kcsan.rst @@ -91,6 +91,16 @@ the below options are available: behaviour when encountering a data race is deemed safe. Please see `"Marking Shared-Memory Accesses" in the LKMM`_ for more information. +* Similar to ``data_race(...)``, the type qualifier ``__data_racy`` can be used + to document that all data races due to accesses to a variable are intended + and should be ignored by KCSAN:: + + struct foo { + ... + int __data_racy stats_counter; + ... + }; + * Disabling data race detection for entire functions can be accomplished by using the function attribute ``__no_kcsan``:: diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 2abaa3a825a9..a38162a8590d 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -273,9 +273,16 @@ struct ftrace_likely_data { * disable all instrumentation. See Kconfig.kcsan where this is mandatory. */ # define __no_kcsan __no_sanitize_thread __disable_sanitizer_instrumentation +/* + * Type qualifier to mark variables where all data-racy accesses should be + * ignored by KCSAN. Note, the implementation simply marks these variables as + * volatile, since KCSAN will treat such accesses as "marked". + */ +# define __data_racy volatile # define __no_sanitize_or_inline __no_kcsan notrace __maybe_unused #else # define __no_kcsan +# define __data_racy #endif #ifndef __no_sanitize_or_inline diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c index 015586217875..0c17b4c83e1c 100644 --- a/kernel/kcsan/kcsan_test.c +++ b/kernel/kcsan/kcsan_test.c @@ -304,6 +304,7 @@ static long test_array[3 * PAGE_SIZE / sizeof(long)]; static struct { long val[8]; } test_struct; +static long __data_racy test_data_racy; static DEFINE_SEQLOCK(test_seqlock); static DEFINE_SPINLOCK(test_spinlock); static DEFINE_MUTEX(test_mutex); @@ -358,6 +359,8 @@ static noinline void test_kernel_write_uninstrumented(void) { test_var++; } static noinline void test_kernel_data_race(void) { data_race(test_var++); } +static noinline void test_kernel_data_racy_qualifier(void) { test_data_racy++; } + static noinline void test_kernel_assert_writer(void) { ASSERT_EXCLUSIVE_WRITER(test_var); @@ -1009,6 +1012,19 @@ static void test_data_race(struct kunit *test) KUNIT_EXPECT_FALSE(test, match_never); } +/* Test the __data_racy type qualifier. */ +__no_kcsan +static void test_data_racy_qualifier(struct kunit *test) +{ + bool match_never = false; + + begin_test_checks(test_kernel_data_racy_qualifier, test_kernel_data_racy_qualifier); + do { + match_never = report_available(); + } while (!end_test_checks(match_never)); + KUNIT_EXPECT_FALSE(test, match_never); +} + __no_kcsan static void test_assert_exclusive_writer(struct kunit *test) { @@ -1424,6 +1440,7 @@ static struct kunit_case kcsan_test_cases[] = { KCSAN_KUNIT_CASE(test_read_plain_atomic_rmw), KCSAN_KUNIT_CASE(test_zero_size_access), KCSAN_KUNIT_CASE(test_data_race), + KCSAN_KUNIT_CASE(test_data_racy_qualifier), KCSAN_KUNIT_CASE(test_assert_exclusive_writer), KCSAN_KUNIT_CASE(test_assert_exclusive_access), KCSAN_KUNIT_CASE(test_assert_exclusive_access_writer), -- cgit v1.2.3 From b1be5844c1a0124a49a30a20a189d0a53aa10578 Mon Sep 17 00:00:00 2001 From: Xining Xu Date: Tue, 7 May 2024 15:27:57 +1200 Subject: scripts: checkpatch: check unused parameters for function-like macro If function-like macros do not utilize a parameter, it might result in a build warning. In our coding style guidelines, we advocate for utilizing static inline functions to replace such macros. This patch verifies compliance with the new rule. For a macro such as the one below, #define test(a) do { } while (0) The test result is as follows. WARNING: Argument 'a' is not used in function-like macro #21: FILE: mm/init-mm.c:20: +#define test(a) do { } while (0) total: 0 errors, 1 warnings, 8 lines checked Link: https://lkml.kernel.org/r/20240507032757.146386-3-21cnbao@gmail.com Signed-off-by: Xining Xu Tested-by: Barry Song Signed-off-by: Barry Song Acked-by: Joe Perches Cc: Chris Zankel Cc: Huacai Chen Cc: Herbert Xu Cc: Guenter Roeck Cc: Stephen Rothwell Cc: Mark Brown Cc: Andy Whitcroft Cc: Dwaipayan Ray Cc: Jonathan Corbet Cc: Lukas Bulwahn Cc: Max Filippov Cc: Jeff Johnson Cc: Charlemagne Lasse Signed-off-by: Andrew Morton --- Documentation/dev-tools/checkpatch.rst | 14 ++++++++++++++ scripts/checkpatch.pl | 6 ++++++ 2 files changed, 20 insertions(+) (limited to 'Documentation/dev-tools') diff --git a/Documentation/dev-tools/checkpatch.rst b/Documentation/dev-tools/checkpatch.rst index 127968995847..a9fac978a525 100644 --- a/Documentation/dev-tools/checkpatch.rst +++ b/Documentation/dev-tools/checkpatch.rst @@ -906,6 +906,20 @@ Macros, Attributes and Symbols See: https://lore.kernel.org/lkml/1399671106.2912.21.camel@joe-AO725/ + **MACRO_ARG_UNUSED** + If function-like macros do not utilize a parameter, it might result + in a build warning. We advocate for utilizing static inline functions + to replace such macros. + For example, for a macro such as the one below:: + + #define test(a) do { } while (0) + + there would be a warning like below:: + + WARNING: Argument 'a' is not used in function-like macro. + + See: https://www.kernel.org/doc/html/latest/process/coding-style.html#macros-enums-and-rtl + **SINGLE_STATEMENT_DO_WHILE_MACRO** For the multi-statement macros, it is necessary to use the do-while loop to avoid unpredictable code paths. The do-while loop helps to diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl index 9c4c4a61bc83..2b812210b412 100755 --- a/scripts/checkpatch.pl +++ b/scripts/checkpatch.pl @@ -6040,6 +6040,12 @@ sub process { CHK("MACRO_ARG_PRECEDENCE", "Macro argument '$arg' may be better as '($arg)' to avoid precedence issues\n" . "$herectx"); } + +# check if this is an unused argument + if ($define_stmt !~ /\b$arg\b/) { + WARN("MACRO_ARG_UNUSED", + "Argument '$arg' is not used in function-like macro\n" . "$herectx"); + } } # check for macros with flow control, but without ## concatenation -- cgit v1.2.3