LibC: Implement dummy rename() so vim can save files

vim calls rename when saving a file. This patch adds dummy
implementation that only works for regular files and does a copy instead
of proper rename.

kernel/kernel/Scheduler.cpp

@@ -330,11 +330,13 @@ namespace Kernel
 		{
 			if (!node->blocked)
 				return;
-			m_block_queue.remove_node(node);
+			if (node != m_current)
+				m_block_queue.remove_node(node);
 			if (node->blocker)
 				node->blocker->remove_blocked_thread(node);
 			node->blocked = false;
-			m_run_queue.add_thread_to_back(node);
+			if (node != m_current)
+				m_run_queue.add_thread_to_back(node);
 		}
 		else
 		{
@@ -467,6 +469,9 @@ namespace Kernel
 				break;
 			if (thread_info.node == m_current || thread_info.queue == nullptr)
 				continue;
+			// FIXME: allow load balancing with blocked threads, with this algorithm there is a race condition
+			if (thread_info.node->blocked)
+				continue;
 
 			auto least_loaded_id = find_least_loaded_processor();
 			if (least_loaded_id == Processor::current_id())

kernel/kernel/Terminal/VirtualTTY.cpp

@@ -245,19 +245,34 @@ namespace Kernel
 			case 'L': // Insert Line
 				if (m_ansi_state.nums[0] == -1)
 					m_ansi_state.nums[0] = 1;
-				for (uint32_t y_off = 0; y_off < (uint32_t)m_ansi_state.nums[0]; y_off++)
+				for (uint32_t row = m_height; row > m_row; row--)
 				{
-					const uint32_t src_y = m_row + y_off;
-					const uint32_t dst_y = src_y + m_ansi_state.nums[0];
-					if (dst_y < m_height)
-					{
-						memcpy(&m_buffer[dst_y * m_width], &m_buffer[src_y * m_width], m_width * sizeof(Cell));
-						for (uint32_t x = 0; x < m_width; x++)
-							render_from_buffer(x, dst_y);
-					}
+					const uint32_t dst_y = row - 1;
+					const uint32_t src_y = dst_y - m_ansi_state.nums[0];
+					memcpy(&m_buffer[dst_y * m_width], &m_buffer[src_y * m_width], m_width * sizeof(Cell));
 					for (uint32_t x = 0; x < m_width; x++)
-						putchar_at(' ', x, src_y);
+						render_from_buffer(x, dst_y);
 				}
+				for (uint32_t y_off = 0; y_off < (uint32_t)m_ansi_state.nums[0] && m_row + y_off < m_height; y_off++)
+					for (uint32_t x = 0; x < m_width; x++)
+						putchar_at(' ', x, m_row + y_off);
+				return reset_ansi();
+			case 'M':
+				if (m_ansi_state.nums[0] == -1)
+					m_ansi_state.nums[0] = 1;
+				if (m_row + m_ansi_state.nums[0] >= m_height)
+					m_ansi_state.nums[0] = m_height - m_row - 1;
+				for (uint32_t row = m_row; row < m_height; row++)
+				{
+					const uint32_t dst_y = row;
+					const uint32_t src_y = dst_y + m_ansi_state.nums[0];
+					memcpy(&m_buffer[dst_y * m_width], &m_buffer[src_y * m_width], m_width * sizeof(Cell));
+					for (uint32_t x = 0; x < m_width; x++)
+						render_from_buffer(x, dst_y);
+				}
+				for (uint32_t y_off = 0; y_off < (uint32_t)m_ansi_state.nums[0]; y_off++)
+					for (uint32_t x = 0; x < m_width; x++)
+						putchar_at(' ', x, m_height - y_off - 1);
 				return reset_ansi();
 			case 'S': // Scroll Up
 				dprintln("Unsupported ANSI CSI character S");

userspace/libraries/LibC/stdio.cpp

@@ -604,11 +604,55 @@ int remove(const char* path)
 	return unlink(path);
 }
 
-// TODO
 int rename(const char* old, const char* _new)
 {
-    dwarnln("rename({}, {})", old, _new);
-    ASSERT_NOT_REACHED();
+	struct stat st;
+	if (lstat(old, &st) == -1)
+		return -1;
+
+	if (!S_ISREG(st.st_mode))
+	{
+		errno = ENOTSUP;
+		return -1;
+	}
+
+	if (unlink(_new) == -1 && errno != ENOENT)
+		return -1;
+
+	int old_fd = open(old, O_RDWR);
+	int new_fd = open(_new, O_RDWR | O_CREAT | O_EXCL, st.st_mode);
+	if (old_fd == -1 || new_fd == -1)
+		goto error;
+
+	for (;;)
+	{
+		char buffer[512];
+		ssize_t nread = read(old_fd, buffer, sizeof(buffer));
+		if (nread == -1)
+		{
+			unlink(_new);
+			goto error;
+		}
+		if (nread == 0)
+			break;
+
+		if (write(new_fd, buffer, nread) != nread)
+		{
+			unlink(_new);
+			goto error;
+		}
+	}
+
+	unlink(old);
+
+	return 0;
+
+error:
+	if (old_fd != -1)
+		close(old_fd);
+	if (new_fd != -1)
+		close(new_fd);
+	return -1;
 }
 
 void rewind(FILE* file)