Kernel/LibC: Implement basic epoll

This implementation is on top of inodes instead of fds as linux does it.
If I start finding ports/software that relies on epoll allowing
duplicate inodes, I will do what linux does.

I'm probably missing multiple epoll_notify's which may cause hangs but
the system seems to work fine :dd:

userspace/libraries/LibC/CMakeLists.txt

@@ -30,6 +30,7 @@ set(LIBC_SOURCES
 	string.cpp
 	strings.cpp
 	sys/banan-os.cpp
+	sys/epoll.cpp
 	sys/ioctl.cpp
 	sys/mman.cpp
 	sys/resource.cpp

userspace/libraries/LibC/include/sys/epoll.h

@@ -0,0 +1,49 @@
+#ifndef _SYS_EPOLL_H
+#define _SYS_EPOLL_H 1
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+#include <stdint.h>
+#include <signal.h>
+
+union epoll_data
+{
+	void* ptr;
+	int fd;
+	uint32_t u32;
+	uint64_t u64;
+};
+typedef union epoll_data epoll_data_t;
+
+struct epoll_event
+{
+	uint32_t events;
+	epoll_data_t data;
+};
+
+#define EPOLL_CTL_ADD 0
+#define EPOLL_CTL_MOD 1
+#define EPOLL_CTL_DEL 2
+
+#define EPOLLIN      0x01
+#define EPOLLOUT     0x02
+#define EPOLLPRI     0x04
+#define EPOLLERR     0x08
+#define EPOLLHUP     0x10
+#define EPOLLET      0x20
+#define EPOLLONESHOT 0x40
+
+#define EPOLL_CLOEXEC 1
+
+int epoll_create(int size);
+int epoll_create1(int flags);
+int epoll_ctl(int epfd, int op, int fd, struct epoll_event* event);
+int epoll_wait(int epfd, struct epoll_event* events, int maxevents, int timeout);
+int epoll_pwait(int epfd, struct epoll_event* events, int maxevents, int timeout, const sigset_t* sigmask);
+int epoll_pwait2(int epfd, struct epoll_event* events, int maxevents, const struct timespec* timeout, const sigset_t* sigmask);
+
+__END_DECLS
+
+#endif

userspace/libraries/LibC/include/sys/syscall.h

@@ -98,6 +98,9 @@ __BEGIN_DECLS
 	O(SYS_PTHREAD_EXIT,		pthread_exit)	\
 	O(SYS_PTHREAD_JOIN,		pthread_join)	\
 	O(SYS_PTHREAD_SELF,		pthread_self)	\
+	O(SYS_EPOLL_CREATE1,	epoll_create1)	\
+	O(SYS_EPOLL_CTL,		epoll_ctl)		\
+	O(SYS_EPOLL_PWAIT2,		epoll_pwait2)	\
 
 enum Syscall
 {

userspace/libraries/LibC/sys/epoll.cpp

@@ -0,0 +1,49 @@
+#include <errno.h>
+#include <unistd.h>
+#include <sys/epoll.h>
+#include <sys/syscall.h>
+
+int epoll_create(int size)
+{
+	if (size <= 0)
+	{
+		errno = EINVAL;
+		return -1;
+	}
+
+	return epoll_create1(0);
+}
+
+int epoll_create1(int flags)
+{
+	return syscall(SYS_EPOLL_CREATE1, flags);
+}
+
+int epoll_ctl(int epfd, int op, int fd, struct epoll_event* event)
+{
+	return syscall(SYS_EPOLL_CTL, epfd, op, fd, event);
+}
+
+int epoll_wait(int epfd, struct epoll_event* events, int maxevents, int timeout)
+{
+	return epoll_pwait(epfd, events, maxevents, timeout, nullptr);
+}
+
+int epoll_pwait(int epfd, struct epoll_event* events, int maxevents, int timeout, const sigset_t* sigmask)
+{
+	timespec ts;
+	timespec* ts_ptr = nullptr;
+	if (timeout >= 0)
+	{
+		ts.tv_sec = static_cast<time_t>(timeout / 1000),
+		ts.tv_nsec = (timeout % 1000) * 1'000'000,
+		ts_ptr = &ts;
+	}
+
+	return epoll_pwait2(epfd, events, maxevents, ts_ptr, sigmask);
+}
+
+int epoll_pwait2(int epfd, struct epoll_event* events, int maxevents, const struct timespec* timeout, const sigset_t* sigmask)
+{
+	return syscall(SYS_EPOLL_PWAIT2, epfd, events, maxevents, timeout, sigmask);
+}