selftests: introduce additional eventfd test coverage

Add several new test cases which assert corner cases on the eventfd
mechanism, for example, the supplied buffer is less than 8 bytes,
attempting to write a value that is too large, etc.

	./eventfd_test
	# Starting 9 tests from 1 test cases.
	#  RUN           global.eventfd_check_flag_rdwr ...
	#            OK  global.eventfd_check_flag_rdwr
	ok 1 global.eventfd_check_flag_rdwr
	#  RUN           global.eventfd_check_flag_cloexec ...
	#            OK  global.eventfd_check_flag_cloexec
	ok 2 global.eventfd_check_flag_cloexec
	#  RUN           global.eventfd_check_flag_nonblock ...
	#            OK  global.eventfd_check_flag_nonblock
	ok 3 global.eventfd_check_flag_nonblock
	#  RUN           global.eventfd_chek_flag_cloexec_and_nonblock ...
	#            OK  global.eventfd_chek_flag_cloexec_and_nonblock
	ok 4 global.eventfd_chek_flag_cloexec_and_nonblock
	#  RUN           global.eventfd_check_flag_semaphore ...
	#            OK  global.eventfd_check_flag_semaphore
	ok 5 global.eventfd_check_flag_semaphore
	#  RUN           global.eventfd_check_write ...
	#            OK  global.eventfd_check_write
	ok 6 global.eventfd_check_write
	#  RUN           global.eventfd_check_read ...
	#            OK  global.eventfd_check_read
	ok 7 global.eventfd_check_read
	#  RUN           global.eventfd_check_read_with_nonsemaphore ...
	#            OK  global.eventfd_check_read_with_nonsemaphore
	ok 8 global.eventfd_check_read_with_nonsemaphore
	#  RUN           global.eventfd_check_read_with_semaphore ...
	#            OK  global.eventfd_check_read_with_semaphore
	ok 9 global.eventfd_check_read_with_semaphore
	# PASSED: 9 / 9 tests passed.
	# Totals: pass:9 fail:0 xfail:0 xpass:0 skip:0 error:0

Link: https://lkml.kernel.org/r/20240527000200.5615-1-wen.yang@linux.devSigned-off-by: Wen Yang <wen.yang@linux.dev>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Andrei Vagin <avagin@google.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Dave Young <dyoung@redhat.com>
Cc: Tim Bird <tim.bird@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/filesystems/eventfd/eventfd_test.c

@@ -13,6 +13,8 @@
 #include <sys/eventfd.h>
 #include "../../kselftest_harness.h"
 
+#define EVENTFD_TEST_ITERATIONS 100000UL
+
 struct error {
 	int  code;
 	char msg[512];
@@ -40,7 +42,7 @@ static inline int sys_eventfd2(unsigned int count, int flags)
 	return syscall(__NR_eventfd2, count, flags);
 }
 
-TEST(eventfd01)
+TEST(eventfd_check_flag_rdwr)
 {
 	int fd, flags;
 
@@ -54,7 +56,7 @@ TEST(eventfd01)
 	close(fd);
 }
 
-TEST(eventfd02)
+TEST(eventfd_check_flag_cloexec)
 {
 	int fd, flags;
 
@@ -68,7 +70,7 @@ TEST(eventfd02)
 	close(fd);
 }
 
-TEST(eventfd03)
+TEST(eventfd_check_flag_nonblock)
 {
 	int fd, flags;
 
@@ -83,7 +85,7 @@ TEST(eventfd03)
 	close(fd);
 }
 
-TEST(eventfd04)
+TEST(eventfd_chek_flag_cloexec_and_nonblock)
 {
 	int fd, flags;
 
@@ -161,7 +163,7 @@ static int verify_fdinfo(int fd, struct error *err, const char *prefix,
 	return 0;
 }
 
-TEST(eventfd05)
+TEST(eventfd_check_flag_semaphore)
 {
 	struct error err = {0};
 	int fd, ret;
@@ -183,4 +185,128 @@ TEST(eventfd05)
 	close(fd);
 }
 
+/*
+ * A write(2) fails with the error EINVAL if the size of the supplied buffer
+ * is less than 8 bytes, or if an attempt is made to write the value
+ * 0xffffffffffffffff.
+ */
+TEST(eventfd_check_write)
+{
+	uint64_t value = 1;
+	ssize_t size;
+	int fd;
+
+	fd = sys_eventfd2(0, 0);
+	ASSERT_GE(fd, 0);
+
+	size = write(fd, &value, sizeof(int));
+	EXPECT_EQ(size, -1);
+	EXPECT_EQ(errno, EINVAL);
+
+	size = write(fd, &value, sizeof(value));
+	EXPECT_EQ(size, sizeof(value));
+
+	value = (uint64_t)-1;
+	size = write(fd, &value, sizeof(value));
+	EXPECT_EQ(size, -1);
+	EXPECT_EQ(errno, EINVAL);
+
+	close(fd);
+}
+
+/*
+ * A read(2) fails with the error EINVAL if the size of the supplied buffer is
+ * less than 8 bytes.
+ */
+TEST(eventfd_check_read)
+{
+	uint64_t value;
+	ssize_t size;
+	int fd;
+
+	fd = sys_eventfd2(1, 0);
+	ASSERT_GE(fd, 0);
+
+	size = read(fd, &value, sizeof(int));
+	EXPECT_EQ(size, -1);
+	EXPECT_EQ(errno, EINVAL);
+
+	size = read(fd, &value, sizeof(value));
+	EXPECT_EQ(size, sizeof(value));
+	EXPECT_EQ(value, 1);
+
+	close(fd);
+}
+
+
+/*
+ * If EFD_SEMAPHORE was not specified and the eventfd counter has a nonzero
+ * value, then a read(2) returns 8 bytes containing that value, and the
+ * counter's value is reset to zero.
+ * If the eventfd counter is zero at the time of the call to read(2), then the
+ * call fails with the error EAGAIN if the file descriptor has been made nonblocking.
+ */
+TEST(eventfd_check_read_with_nonsemaphore)
+{
+	uint64_t value;
+	ssize_t size;
+	int fd;
+	int i;
+
+	fd = sys_eventfd2(0, EFD_NONBLOCK);
+	ASSERT_GE(fd, 0);
+
+	value = 1;
+	for (i = 0; i < EVENTFD_TEST_ITERATIONS; i++) {
+		size = write(fd, &value, sizeof(value));
+		EXPECT_EQ(size, sizeof(value));
+	}
+
+	size = read(fd, &value, sizeof(value));
+	EXPECT_EQ(size, sizeof(uint64_t));
+	EXPECT_EQ(value, EVENTFD_TEST_ITERATIONS);
+
+	size = read(fd, &value, sizeof(value));
+	EXPECT_EQ(size, -1);
+	EXPECT_EQ(errno, EAGAIN);
+
+	close(fd);
+}
+
+/*
+ * If EFD_SEMAPHORE was specified and the eventfd counter has a nonzero value,
+ * then a read(2) returns 8 bytes containing the value 1, and the counter's
+ * value is decremented by 1.
+ * If the eventfd counter is zero at the time of the call to read(2), then the
+ * call fails with the error EAGAIN if the file descriptor has been made nonblocking.
+ */
+TEST(eventfd_check_read_with_semaphore)
+{
+	uint64_t value;
+	ssize_t size;
+	int fd;
+	int i;
+
+	fd = sys_eventfd2(0, EFD_SEMAPHORE|EFD_NONBLOCK);
+	ASSERT_GE(fd, 0);
+
+	value = 1;
+	for (i = 0; i < EVENTFD_TEST_ITERATIONS; i++) {
+		size = write(fd, &value, sizeof(value));
+		EXPECT_EQ(size, sizeof(value));
+	}
+
+	for (i = 0; i < EVENTFD_TEST_ITERATIONS; i++) {
+		size = read(fd, &value, sizeof(value));
+		EXPECT_EQ(size, sizeof(value));
+		EXPECT_EQ(value, 1);
+	}
+
+	size = read(fd, &value, sizeof(value));
+	EXPECT_EQ(size, -1);
+	EXPECT_EQ(errno, EAGAIN);
+
+	close(fd);
+}
+
 TEST_HARNESS_MAIN