[PATCH] selftests: introduce additional eventfd test coverage

[Wen Yang <wen.yang@linux.dev>]

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.eventfd01 ...
	#            OK  global.eventfd01
	ok 1 global.eventfd01
	#  RUN           global.eventfd02 ...
	#            OK  global.eventfd02
	ok 2 global.eventfd02
	#  RUN           global.eventfd03 ...
	#            OK  global.eventfd03
	ok 3 global.eventfd03
	#  RUN           global.eventfd04 ...
	#            OK  global.eventfd04
	ok 4 global.eventfd04
	#  RUN           global.eventfd05 ...
	#            OK  global.eventfd05
	ok 5 global.eventfd05
	#  RUN           global.eventfd06 ...
	#            OK  global.eventfd06
	ok 6 global.eventfd06
	#  RUN           global.eventfd07 ...
	#            OK  global.eventfd07
	ok 7 global.eventfd07
	#  RUN           global.eventfd08 ...
	#            OK  global.eventfd08
	ok 8 global.eventfd08
	#  RUN           global.eventfd09 ...
	#            OK  global.eventfd09
	ok 9 global.eventfd09
	# PASSED: 9 / 9 tests passed.
	# Totals: pass:9 fail:0 xfail:0 xpass:0 skip:0 error:0

Signed-off-by: Wen Yang <wen.yang@linux.dev>
Cc: SShuah 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: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Young <dyoung@redhat.com>
Cc: linux-kselftest@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 .../filesystems/eventfd/eventfd_test.c        | 116 ++++++++++++++++++
 1 file changed, 116 insertions(+)

diff --git a/tools/testing/selftests/filesystems/eventfd/eventfd_test.c b/tools/testing/selftests/filesystems/eventfd/eventfd_test.c
index f142a137526c..eeab8df5b1b5 100644
--- a/tools/testing/selftests/filesystems/eventfd/eventfd_test.c
+++ b/tools/testing/selftests/filesystems/eventfd/eventfd_test.c
@@ -183,4 +183,120 @@ 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(eventfd06)
+{
+	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);
+
+	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(eventfd07)
+{
+	int value = 0;
+	ssize_t size;
+	int fd;
+
+	fd = sys_eventfd2(0, 0);
+	ASSERT_GE(fd, 0);
+
+	size = write(fd, &value, sizeof(value));
+	EXPECT_EQ(size, -1);
+	EXPECT_EQ(errno, EINVAL);
+
+	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(eventfd08)
+{
+	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 < 10000000; 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, 10000000);
+
+	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(eventfd09)
+{
+	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 < 10000000; i++) {
+		size = write(fd, &value, sizeof(value));
+		EXPECT_EQ(size, sizeof(value));
+	}
+
+	for (i = 0; i < 10000000; 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
-- 
2.25.1