tools/nolibc: add timerfd functionality

This is used in various selftests and will be handy when integrating
those with nolibc.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20250428-nolibc-misc-v2-10-3c043eeab06c@linutronix.de
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

tools/include/nolibc/Makefile

@@ -53,6 +53,7 @@ all_files := \
 		sys/stat.h \
 		sys/syscall.h \
 		sys/time.h \
+		sys/timerfd.h \
 		sys/types.h \
 		sys/wait.h \
 		time.h \

tools/include/nolibc/nolibc.h

@@ -102,6 +102,7 @@
 #include "sys/stat.h"
 #include "sys/syscall.h"
 #include "sys/time.h"
+#include "sys/timerfd.h"
 #include "sys/wait.h"
 #include "ctype.h"
 #include "elf.h"

tools/include/nolibc/sys/timerfd.h

@@ -0,0 +1,87 @@
+/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
+/*
+ * timerfd definitions for NOLIBC
+ * Copyright (C) 2025 Thomas Weißschuh <thomas.weissschuh@linutronix.de>
+ */
+
+/* make sure to include all global symbols */
+#include "../nolibc.h"
+
+#ifndef _NOLIBC_SYS_TIMERFD_H
+#define _NOLIBC_SYS_TIMERFD_H
+
+#include "../sys.h"
+#include "../time.h"
+
+#include <linux/timerfd.h>
+
+
+static __attribute__((unused))
+int sys_timerfd_create(int clockid, int flags)
+{
+	return my_syscall2(__NR_timerfd_create, clockid, flags);
+}
+
+static __attribute__((unused))
+int timerfd_create(int clockid, int flags)
+{
+	return __sysret(sys_timerfd_create(clockid, flags));
+}
+
+
+static __attribute__((unused))
+int sys_timerfd_gettime(int fd, struct itimerspec *curr_value)
+{
+#if defined(__NR_timerfd_gettime)
+	return my_syscall2(__NR_timerfd_gettime, fd, curr_value);
+#elif defined(__NR_timerfd_gettime64)
+	struct __kernel_itimerspec kcurr_value;
+	int ret;
+
+	ret = my_syscall2(__NR_timerfd_gettime64, fd, &kcurr_value);
+	__nolibc_timespec_kernel_to_user(&kcurr_value.it_interval, &curr_value->it_interval);
+	__nolibc_timespec_kernel_to_user(&kcurr_value.it_value, &curr_value->it_value);
+	return ret;
+#else
+	return __nolibc_enosys(__func__, fd, curr_value);
+#endif
+}
+
+static __attribute__((unused))
+int timerfd_gettime(int fd, struct itimerspec *curr_value)
+{
+	return __sysret(sys_timerfd_gettime(fd, curr_value));
+}
+
+
+static __attribute__((unused))
+int sys_timerfd_settime(int fd, int flags,
+			const struct itimerspec *new_value, struct itimerspec *old_value)
+{
+#if defined(__NR_timerfd_settime)
+	return my_syscall4(__NR_timerfd_settime, fd, flags, new_value, old_value);
+#elif defined(__NR_timerfd_settime64)
+	struct __kernel_itimerspec knew_value, kold_value;
+	int ret;
+
+	__nolibc_timespec_user_to_kernel(&new_value->it_value, &knew_value.it_value);
+	__nolibc_timespec_user_to_kernel(&new_value->it_interval, &knew_value.it_interval);
+	ret = my_syscall4(__NR_timerfd_settime64, fd, flags, &knew_value, &kold_value);
+	if (old_value) {
+		__nolibc_timespec_kernel_to_user(&kold_value.it_interval, &old_value->it_interval);
+		__nolibc_timespec_kernel_to_user(&kold_value.it_value, &old_value->it_value);
+	}
+	return ret;
+#else
+	return __nolibc_enosys(__func__, fd, flags, new_value, old_value);
+#endif
+}
+
+static __attribute__((unused))
+int timerfd_settime(int fd, int flags,
+		    const struct itimerspec *new_value, struct itimerspec *old_value)
+{
+	return __sysret(sys_timerfd_settime(fd, flags, new_value, old_value));
+}
+
+#endif /* _NOLIBC_SYS_TIMERFD_H */

tools/testing/selftests/nolibc/nolibc-test.c

@@ -27,6 +27,7 @@
 #include <sys/syscall.h>
 #include <sys/sysmacros.h>
 #include <sys/time.h>
+#include <sys/timerfd.h>
 #include <sys/utsname.h>
 #include <sys/wait.h>
 #include <dirent.h>
@@ -955,6 +956,52 @@ int test_timer(void)
 	return ret;
 }
 
+int test_timerfd(void)
+{
+	struct itimerspec timerspec;
+	int timer, ret;
+
+	timer = timerfd_create(CLOCK_MONOTONIC, 0);
+	if (timer == -1)
+		return -1;
+
+	timerspec = (struct itimerspec) {
+		.it_value.tv_sec = 1000000,
+	};
+	ret = timerfd_settime(timer, 0, &timerspec, NULL);
+	if (ret)
+		goto err;
+
+	timerspec = (struct itimerspec) {
+		.it_value.tv_sec = -1,
+		.it_value.tv_nsec = -1,
+		.it_interval.tv_sec = -1,
+		.it_interval.tv_nsec = -1,
+	};
+	ret = timerfd_gettime(timer, &timerspec);
+	if (ret)
+		goto err;
+
+	errno = EINVAL;
+	ret = -1;
+
+	if (timerspec.it_interval.tv_sec || timerspec.it_interval.tv_nsec)
+		goto err;
+
+	if (timerspec.it_value.tv_sec > 1000000)
+		goto err;
+
+	ret = close(timer);
+	if (ret)
+		return ret;
+
+	return 0;
+
+err:
+	close(timer);
+	return ret;
+}
+
 int test_uname(void)
 {
 	struct utsname buf;
@@ -1237,6 +1284,7 @@ int run_syscall(int min, int max)
 		CASE_TEST(stat_timestamps);   EXPECT_SYSZR(1, test_stat_timestamps()); break;
 		CASE_TEST(symlink_root);      EXPECT_SYSER(1, symlink("/", "/"), -1, EEXIST); break;
 		CASE_TEST(timer);             EXPECT_SYSZR(1, test_timer()); break;
+		CASE_TEST(timerfd);           EXPECT_SYSZR(1, test_timerfd()); break;
 		CASE_TEST(uname);             EXPECT_SYSZR(proc, test_uname()); break;
 		CASE_TEST(uname_fault);       EXPECT_SYSER(1, uname(NULL), -1, EFAULT); break;
 		CASE_TEST(unlink_root);       EXPECT_SYSER(1, unlink("/"), -1, EISDIR); break;