Kernel: add basic fcntl() with couple of commands and no validation

kernel/include/kernel/OpenFileDescriptorSet.h

@@ -28,6 +28,8 @@ namespace Kernel
 		BAN::ErrorOr<int> dup(int);
 		BAN::ErrorOr<int> dup2(int, int);
 
+		BAN::ErrorOr<int> fcntl(int fd, int cmd, int extra);
+
 		BAN::ErrorOr<void> seek(int fd, off_t offset, int whence);
 		BAN::ErrorOr<off_t> tell(int) const;
 

kernel/include/kernel/Process.h

@@ -99,6 +99,8 @@ namespace Kernel
 		BAN::ErrorOr<long> sys_dup(int fildes);
 		BAN::ErrorOr<long> sys_dup2(int fildes, int fildes2);
 
+		BAN::ErrorOr<long> sys_fcntl(int fildes, int cmd, int extra);
+
 		BAN::ErrorOr<long> sys_seek(int fd, off_t offset, int whence);
 		BAN::ErrorOr<long> sys_tell(int fd);
 

kernel/kernel/OpenFileDescriptorSet.cpp

@@ -118,6 +118,32 @@ namespace Kernel
 		return fildes;
 	}
 
+	BAN::ErrorOr<int> OpenFileDescriptorSet::fcntl(int fd, int cmd, int extra)
+	{
+		TRY(validate_fd(fd));
+
+		constexpr int creation_flags = O_CLOEXEC | O_CREAT | O_DIRECTORY | O_EXCL | O_NOCTTY | O_NOFOLLOW | O_TRUNC | O_TTY_INIT;
+
+		switch (cmd)
+		{
+			case F_GETFD:
+				return m_open_files[fd]->flags;
+			case F_SETFD:
+				// FIXME: validate permissions to set access flags
+				m_open_files[fd]->flags = extra;
+				return 0;
+			case F_GETFL:
+				return m_open_files[fd]->flags & ~creation_flags;
+			case F_SETFL:
+				m_open_files[fd]->flags |= extra & ~(O_ACCMODE | creation_flags);
+				return 0;
+			default:
+				break;
+		}
+		
+		return BAN::Error::from_errno(ENOTSUP);
+	}
+
 	BAN::ErrorOr<void> OpenFileDescriptorSet::seek(int fd, off_t offset, int whence)
 	{
 		TRY(validate_fd(fd));

kernel/kernel/Process.cpp

@@ -669,6 +669,12 @@ namespace Kernel
 		return TRY(m_open_file_descriptors.dup2(fildes, fildes2));
 	}
 
+	BAN::ErrorOr<long> Process::sys_fcntl(int fildes, int cmd, int extra)
+	{
+		LockGuard _(m_lock);
+		return TRY(m_open_file_descriptors.fcntl(fildes, cmd, extra));
+	}
+
 	BAN::ErrorOr<long> Process::sys_seek(int fd, off_t offset, int whence)
 	{
 		LockGuard _(m_lock);

kernel/kernel/Syscall.cpp

@@ -179,6 +179,9 @@ namespace Kernel
 		case SYS_SET_PGID:
 			ret = Process::current().sys_setpgid((pid_t)arg1, (pid_t)arg2);
 			break;
+		case SYS_FCNTL:
+			ret = Process::current().sys_fcntl((int)arg1, (int)arg2, (int)arg3);
+			break;
 		default:
 			dwarnln("Unknown syscall {}", syscall);
 			break;

libc/fcntl.cpp

@@ -23,3 +23,13 @@ int openat(int fd, const char* path, int oflag, ...)
 
 	return syscall(SYS_OPENAT, fd, path, oflag, mode);
 }
+
+int fcntl(int fildes, int cmd, ...)
+{
+	va_list args;
+	va_start(args, cmd);
+	int extra = va_arg(args, int);
+	va_end(args);
+
+	return syscall(SYS_FCNTL, fildes, cmd, extra);
+}

libc/include/sys/syscall.h

@@ -50,6 +50,7 @@ __BEGIN_DECLS
 #define SYS_GET_PID 43
 #define SYS_GET_PGID 44
 #define SYS_SET_PGID 45
+#define SYS_FCNTL 46
 
 __END_DECLS