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

Signed-off-by: Wen Yang <wen.y...@linux.dev>
Cc: SShuah Khan <sh...@kernel.org>
Cc: Christian Brauner <brau...@kernel.org>
Cc: Andrei Vagin <ava...@google.com>
Cc: Mathieu Desnoyers <mathieu.desnoy...@efficios.com>
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Dave Young <dyo...@redhat.com>
Cc: Tim Bird <tim.b...@sony.com>
Cc: linux-kselftest@vger.kernel.org
Cc: linux-ker...@vger.kernel.org
---
v2: use strings which indicate what is being tested, that are useful to a human

 .../filesystems/eventfd/eventfd_test.c        | 136 +++++++++++++++++-
 1 file changed, 131 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/filesystems/eventfd/eventfd_test.c 
b/tools/testing/selftests/filesystems/eventfd/eventfd_test.c
index f142a137526c..85acb4e3ef00 100644
--- a/tools/testing/selftests/filesystems/eventfd/eventfd_test.c
+++ b/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
-- 
2.25.1


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