Kernel/LibC: add dup() syscall and function

kernel/include/kernel/OpenFileDescriptorSet.h

@@ -25,6 +25,7 @@ namespace Kernel
 
 		BAN::ErrorOr<void> pipe(int fds[2]);
 
+		BAN::ErrorOr<int> dup(int);
 		BAN::ErrorOr<int> dup2(int, int);
 
 		BAN::ErrorOr<void> seek(int fd, off_t offset, int whence);

kernel/include/kernel/Process.h

@@ -86,6 +86,7 @@ namespace Kernel
 		BAN::ErrorOr<long> sys_creat(BAN::StringView name, mode_t);
 
 		BAN::ErrorOr<long> sys_pipe(int fildes[2]);
+		BAN::ErrorOr<long> sys_dup(int fildes);
 		BAN::ErrorOr<long> sys_dup2(int fildes, int fildes2);
 
 		BAN::ErrorOr<long> sys_seek(int fd, off_t offset, int whence);

kernel/kernel/OpenFileDescriptorSet.cpp

@@ -85,6 +85,19 @@ namespace Kernel
 		return {};
 	}
 
+	BAN::ErrorOr<int> OpenFileDescriptorSet::dup(int fildes)
+	{
+		TRY(validate_fd(fildes));
+
+		int result = TRY(get_free_fd());
+		m_open_files[result] = m_open_files[fildes];
+		
+		if (m_open_files[result]->flags & O_WRONLY && m_open_files[result]->inode->is_pipe())
+			((Pipe*)m_open_files[result]->inode.ptr())->clone_writing();
+
+		return result;
+	}
+
 	BAN::ErrorOr<int> OpenFileDescriptorSet::dup2(int fildes, int fildes2)
 	{
 		if (fildes2 < 0 || fildes2 >= (int)m_open_files.size())

kernel/kernel/Process.cpp

@@ -596,6 +596,12 @@ namespace Kernel
 		return 0;
 	}
 
+	BAN::ErrorOr<long> Process::sys_dup(int fildes)
+	{
+		LockGuard _(m_lock);
+		return TRY(m_open_file_descriptors.dup(fildes));
+	}
+
 	BAN::ErrorOr<long> Process::sys_dup2(int fildes, int fildes2)
 	{
 		LockGuard _(m_lock);

kernel/kernel/Syscall.cpp

@@ -149,6 +149,9 @@ namespace Kernel
 		case SYS_PIPE:
 			ret = Process::current().sys_pipe((int*)arg1);
 			break;
+		case SYS_DUP:
+			ret = Process::current().sys_dup((int)arg1);
+			break;
 		case SYS_DUP2:
 			ret = Process::current().sys_dup2((int)arg1, (int)arg2);
 			break;