linux-kernel - [tip: timers/urgent] selftests: kselftest: Mark functions that unconditionally call exit() as _

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Date: Fri, 12 Apr 2024 12:15:28 -0000
From: "tip-bot2 for Nathan Chancellor" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: John Stultz <jstultz@...gle.com>, Nathan Chancellor <nathan@...nel.org>,
 Thomas Gleixner <tglx@...utronix.de>, Shuah Khan <skhan@...uxfoundation.org>,
 stable@...r.kernel.org, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: timers/urgent] selftests: kselftest: Mark functions that
 unconditionally call exit() as __noreturn

The following commit has been merged into the timers/urgent branch of tip:

Commit-ID:     f7d5bcd35d427daac7e206b1073ca14f5db85c27
Gitweb:        https://git.kernel.org/tip/f7d5bcd35d427daac7e206b1073ca14f5db85c27
Author:        Nathan Chancellor <nathan@...nel.org>
AuthorDate:    Thu, 11 Apr 2024 11:45:40 -07:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Fri, 12 Apr 2024 14:11:15 +02:00

selftests: kselftest: Mark functions that unconditionally call exit() as __noreturn

After commit 6d029c25b71f ("selftests/timers/posix_timers: Reimplement
check_timer_distribution()"), clang warns:

  tools/testing/selftests/timers/../kselftest.h:398:6: warning: variable 'major' is used uninitialized whenever '||' condition is true [-Wsometimes-uninitialized]
    398 |         if (uname(&info) || sscanf(info.release, "%u.%u.", &major, &minor) != 2)
        |             ^~~~~~~~~~~~
  tools/testing/selftests/timers/../kselftest.h:401:9: note: uninitialized use occurs here
    401 |         return major > min_major || (major == min_major && minor >= min_minor);
        |                ^~~~~
  tools/testing/selftests/timers/../kselftest.h:398:6: note: remove the '||' if its condition is always false
    398 |         if (uname(&info) || sscanf(info.release, "%u.%u.", &major, &minor) != 2)
        |             ^~~~~~~~~~~~~~~
  tools/testing/selftests/timers/../kselftest.h:395:20: note: initialize the variable 'major' to silence this warning
    395 |         unsigned int major, minor;
        |                           ^
        |                            = 0

This is a false positive because if uname() fails, ksft_exit_fail_msg()
will be called, which unconditionally calls exit(), a noreturn function.
However, clang does not know that ksft_exit_fail_msg() will call exit() at
the point in the pipeline that the warning is emitted because inlining has
not occurred, so it assumes control flow will resume normally after
ksft_exit_fail_msg() is called.

Make it clear to clang that all of the functions that call exit()
unconditionally in kselftest.h are noreturn transitively by marking them
explicitly with '__attribute__((__noreturn__))', which clears up the
warning above and any future warnings that may appear for the same reason.

Fixes: 6d029c25b71f ("selftests/timers/posix_timers: Reimplement check_timer_distribution()")
Reported-by: John Stultz <jstultz@...gle.com>
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Shuah Khan <skhan@...uxfoundation.org>
Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/r/20240411-mark-kselftest-exit-funcs-noreturn-v1-1-b027c948f586@kernel.org
Closes: https://lore.kernel.org/all/20240410232637.4135564-2-jstultz@google.com/
---
 tools/testing/selftests/kselftest.h | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/kselftest.h b/tools/testing/selftests/kselftest.h
index 973b18e..0591974 100644
--- a/tools/testing/selftests/kselftest.h
+++ b/tools/testing/selftests/kselftest.h
@@ -80,6 +80,9 @@
 #define KSFT_XPASS 3
 #define KSFT_SKIP  4
 
+#ifndef __noreturn
+#define __noreturn       __attribute__((__noreturn__))
+#endif
 #define __printf(a, b)   __attribute__((format(printf, a, b)))
 
 /* counters */
@@ -300,13 +303,13 @@ void ksft_test_result_code(int exit_code, const char *test_name,
 	va_end(args);
 }
 
-static inline int ksft_exit_pass(void)
+static inline __noreturn int ksft_exit_pass(void)
 {
 	ksft_print_cnts();
 	exit(KSFT_PASS);
 }
 
-static inline int ksft_exit_fail(void)
+static inline __noreturn int ksft_exit_fail(void)
 {
 	ksft_print_cnts();
 	exit(KSFT_FAIL);
@@ -333,7 +336,7 @@ static inline int ksft_exit_fail(void)
 		  ksft_cnt.ksft_xfail +	\
 		  ksft_cnt.ksft_xskip)
 
-static inline __printf(1, 2) int ksft_exit_fail_msg(const char *msg, ...)
+static inline __noreturn __printf(1, 2) int ksft_exit_fail_msg(const char *msg, ...)
 {
 	int saved_errno = errno;
 	va_list args;
@@ -348,19 +351,19 @@ static inline __printf(1, 2) int ksft_exit_fail_msg(const char *msg, ...)
 	exit(KSFT_FAIL);
 }
 
-static inline int ksft_exit_xfail(void)
+static inline __noreturn int ksft_exit_xfail(void)
 {
 	ksft_print_cnts();
 	exit(KSFT_XFAIL);
 }
 
-static inline int ksft_exit_xpass(void)
+static inline __noreturn int ksft_exit_xpass(void)
 {
 	ksft_print_cnts();
 	exit(KSFT_XPASS);
 }
 
-static inline __printf(1, 2) int ksft_exit_skip(const char *msg, ...)
+static inline __noreturn __printf(1, 2) int ksft_exit_skip(const char *msg, ...)
 {
 	int saved_errno = errno;
 	va_list args;