selftests: add eventfd selftests

This adds the promised selftest for eventfd.  It will verify the flags of
eventfd2, including EFD_CLOEXEC, EFD_NONBLOCK and EFD_SEMAPHORE.

Link: https://lkml.kernel.org/r/tencent_3C9A298878D22B5D8F79DC2FEE99BB4A8F05@qq.comSigned-off-by: Wen Yang <wenyang.linux@foxmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Pengfei Xu <pengfei.xu@intel.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: Andrei Vagin <avagin@google.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/filesystems/eventfd/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
+eventfd_test

tools/testing/selftests/filesystems/eventfd/Makefile

+# SPDX-License-Identifier: GPL-2.0
+
+CFLAGS += $(KHDR_INCLUDES)
+LDLIBS += -lpthread
+TEST_GEN_PROGS := eventfd_test
+
+include ../../lib.mk

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

+// SPDX-License-Identifier: GPL-2.0
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <asm/unistd.h>
+#include <linux/time_types.h>
+#include <unistd.h>
+#include <assert.h>
+#include <signal.h>
+#include <pthread.h>
+#include <sys/epoll.h>
+#include <sys/eventfd.h>
+#include "../../kselftest_harness.h"
+
+struct error {
+	int  code;
+	char msg[512];
+};
+
+static int error_set(struct error *err, int code, const char *fmt, ...)
+{
+	va_list args;
+	int r;
+
+	if (code == 0 || !err || err->code != 0)
+		return code;
+
+	err->code = code;
+	va_start(args, fmt);
+	r = vsnprintf(err->msg, sizeof(err->msg), fmt, args);
+	assert((size_t)r < sizeof(err->msg));
+	va_end(args);
+
+	return code;
+}
+
+static inline int sys_eventfd2(unsigned int count, int flags)
+{
+	return syscall(__NR_eventfd2, count, flags);
+}
+
+TEST(eventfd01)
+{
+	int fd, flags;
+
+	fd = sys_eventfd2(0, 0);
+	ASSERT_GE(fd, 0);
+
+	flags = fcntl(fd, F_GETFL);
+	// since the kernel automatically added O_RDWR.
+	EXPECT_EQ(flags, O_RDWR);
+
+	close(fd);
+}
+
+TEST(eventfd02)
+{
+	int fd, flags;
+
+	fd = sys_eventfd2(0, EFD_CLOEXEC);
+	ASSERT_GE(fd, 0);
+
+	flags = fcntl(fd, F_GETFD);
+	ASSERT_GT(flags, -1);
+	EXPECT_EQ(flags, FD_CLOEXEC);
+
+	close(fd);
+}
+
+TEST(eventfd03)
+{
+	int fd, flags;
+
+	fd = sys_eventfd2(0, EFD_NONBLOCK);
+	ASSERT_GE(fd, 0);
+
+	flags = fcntl(fd, F_GETFL);
+	ASSERT_GT(flags, -1);
+	EXPECT_EQ(flags & EFD_NONBLOCK, EFD_NONBLOCK);
+	EXPECT_EQ(flags & O_RDWR, O_RDWR);
+
+	close(fd);
+}
+
+TEST(eventfd04)
+{
+	int fd, flags;
+
+	fd = sys_eventfd2(0, EFD_CLOEXEC|EFD_NONBLOCK);
+	ASSERT_GE(fd, 0);
+
+	flags = fcntl(fd, F_GETFL);
+	ASSERT_GT(flags, -1);
+	EXPECT_EQ(flags & EFD_NONBLOCK, EFD_NONBLOCK);
+	EXPECT_EQ(flags & O_RDWR, O_RDWR);
+
+	flags = fcntl(fd, F_GETFD);
+	ASSERT_GT(flags, -1);
+	EXPECT_EQ(flags, FD_CLOEXEC);
+
+	close(fd);
+}
+
+static inline void trim_newline(char *str)
+{
+	char *pos = strrchr(str, '\n');
+
+	if (pos)
+		*pos = '\0';
+}
+
+static int verify_fdinfo(int fd, struct error *err, const char *prefix,
+		size_t prefix_len, const char *expect, ...)
+{
+	char buffer[512] = {0, };
+	char path[512] = {0, };
+	va_list args;
+	FILE *f;
+	char *line = NULL;
+	size_t n = 0;
+	int found = 0;
+	int r;
+
+	va_start(args, expect);
+	r = vsnprintf(buffer, sizeof(buffer), expect, args);
+	assert((size_t)r < sizeof(buffer));
+	va_end(args);
+
+	snprintf(path, sizeof(path), "/proc/self/fdinfo/%d", fd);
+	f = fopen(path, "re");
+	if (!f)
+		return error_set(err, -1, "fdinfo open failed for %d", fd);
+
+	while (getline(&line, &n, f) != -1) {
+		char *val;
+
+		if (strncmp(line, prefix, prefix_len))
+			continue;
+
+		found = 1;
+
+		val = line + prefix_len;
+		r = strcmp(val, buffer);
+		if (r != 0) {
+			trim_newline(line);
+			trim_newline(buffer);
+			error_set(err, -1, "%s '%s' != '%s'",
+				  prefix, val, buffer);
+		}
+		break;
+	}
+
+	free(line);
+	fclose(f);
+
+	if (found == 0)
+		return error_set(err, -1, "%s not found for fd %d",
+				 prefix, fd);
+
+	return 0;
+}
+
+TEST(eventfd05)
+{
+	struct error err = {0};
+	int fd, ret;
+
+	fd = sys_eventfd2(0, EFD_SEMAPHORE);
+	ASSERT_GE(fd, 0);
+
+	ret = fcntl(fd, F_GETFL);
+	ASSERT_GT(ret, -1);
+	EXPECT_EQ(ret & O_RDWR, O_RDWR);
+
+	// The semaphore could only be obtained from fdinfo.
+	ret = verify_fdinfo(fd, &err, "eventfd-semaphore: ", 19, "1\n");
+	if (ret != 0)
+		ksft_print_msg("eventfd-semaphore check failed, msg: %s\n",
+				err.msg);
+	EXPECT_EQ(ret, 0);
+
+	close(fd);
+}
+
+TEST_HARNESS_MAIN