libc, vfs: rename improvements

Perform POSIX rename checks at the libc VFS plugin.
Clarify rename at VFS fs, ram, single, and tar file systems.

Issue #1900
Fixes #1782

repos/libports/src/lib/libc/vfs_plugin.cc

@@ -775,6 +775,24 @@ int Libc::Vfs_plugin::rename(char const *from_path, char const *to_path)
 {
 	typedef Vfs::Directory_service::Rename_result Result;
 
+	if (_root_dir.leaf_path(to_path)) {
+
+		if (_root_dir.is_directory(to_path)) {
+			if (!_root_dir.is_directory(from_path)) {
+				errno = EISDIR; return -1;
+			}
+
+			if (_root_dir.num_dirent(to_path)) {
+				errno = ENOTEMPTY; return -1;
+			}
+
+		} else {
+			if (_root_dir.is_directory(from_path)) {
+				errno = ENOTDIR; return -1;
+			}
+		}
+	}
+
 	switch (_root_dir.rename(from_path, to_path)) {
 	case Result::RENAME_ERR_NO_ENTRY: errno = ENOENT; return -1;
 	case Result::RENAME_ERR_CROSS_FS: errno = EXDEV;  return -1;

repos/os/include/vfs/fs_file_system.h

@@ -387,6 +387,9 @@ class Vfs::Fs_file_system : public File_system
 
 		Rename_result rename(char const *from_path, char const *to_path) override
 		{
+			if ((strcmp(from_path, to_path) == 0) && leaf_path(from_path))
+				return RENAME_OK;
+
 			Absolute_path from_dir_path(from_path);
 			from_dir_path.strip_last_element();
 			from_dir_path.remove_trailing('/');

repos/os/include/vfs/ram_file_system.h

@@ -353,7 +353,7 @@ class Vfs::Ram_file_system : public Vfs::File_system
 			Directory *dir = &_root;
 
 			char *name = &buf[0];
-			for (size_t i = 0; i < MAX_NAME_LEN; ++i) {
+			for (size_t i = 0; i < MAX_PATH_LEN; ++i) {
 				if (buf[i] == '/') {
 					buf[i] = '\0';
 
@@ -498,6 +498,7 @@ class Vfs::Ram_file_system : public Vfs::File_system
 				return STAT_OK;
 			}
 
+			/* this should never happen */
 			return STAT_ERR_NO_ENTRY;
 		}
 
@@ -575,6 +576,9 @@ class Vfs::Ram_file_system : public Vfs::File_system
 		{
 			using namespace Vfs_ram;
 
+			if ((strcmp(from, to) == 0) && lookup(from))
+				return RENAME_OK;
+
 			char const *new_name = basename(to);
 			if (strlen(new_name) >= MAX_NAME_LEN)
 				return RENAME_ERR_NO_PERM;
@@ -586,28 +590,32 @@ class Vfs::Ram_file_system : public Vfs::File_system
 			Directory *to_dir = lookup_parent(to);
 			if (!to_dir) return RENAME_ERR_NO_ENTRY;
 
-			if (from_dir == to_dir) {
+			/* unlock the node so a second guard can be constructed */
+			if (from_dir == to_dir)
+				from_dir->unlock();
 
-				Node *node = from_dir->child(basename(from));
-				if (!node) return RENAME_ERR_NO_ENTRY;
-				Node::Guard guard(node);
+			Node::Guard to_guard(to_dir);
 
-				if (from_dir->child(new_name)) return RENAME_ERR_NO_PERM;
-				node->name(new_name);
+			Node *from_node = from_dir->child(basename(from));
+			if (!from_node) return RENAME_ERR_NO_ENTRY;
+			Node::Guard guard(from_node);
 
-			} else {
+			Node *to_node = to_dir->child(new_name);
+			if (to_node) {
+				to_node->lock();
 
-				Node::Guard toguard(to_dir);
+				if (Directory *dir = dynamic_cast<Directory*>(to_node))
+					if (dir->length() || (!dynamic_cast<Directory*>(from_node)))
+						return RENAME_ERR_NO_PERM;
 
-				if (to_dir->child(new_name)) return RENAME_ERR_NO_PERM;
-
-				Node *node = from_dir->child(basename(from));
-				if (!node) return RENAME_ERR_NO_ENTRY;
-
-				node->name(new_name);
-				to_dir->adopt(node);
-				from_dir->release(node);
+				to_dir->release(to_node);
+				destroy(_alloc, to_node);
 			}
+
+			from_dir->release(from_node);
+			from_node->name(new_name);
+			to_dir->adopt(from_node);
+
 			return RENAME_OK;
 		}
 

repos/os/include/vfs/single_file_system.h

@@ -124,7 +124,7 @@ class Vfs::Single_file_system : public File_system
 
 		char const *leaf_path(char const *path) override
 		{
-			return path;
+			return _is_single_file(path) ? path : 0;
 		}
 
 		Open_result open(char const *path, unsigned,
@@ -148,9 +148,11 @@ class Vfs::Single_file_system : public File_system
 			return READLINK_ERR_NO_ENTRY;
 		}
 
-		Rename_result rename(char const *, char const *) override
+		Rename_result rename(char const *from, char const *to) override
 		{
-			return RENAME_ERR_NO_PERM;
+			if (_is_single_file(from) || _is_single_file(to))
+				return RENAME_ERR_NO_PERM;
+			return RENAME_ERR_NO_ENTRY;
 		}
 
 		Mkdir_result mkdir(char const *, unsigned) override

repos/os/include/vfs/symlink_file_system.h

@@ -138,8 +138,12 @@ class Vfs::Symlink_file_system : public File_system
 		Unlink_result unlink(char const *) override {
 			return UNLINK_ERR_NO_PERM; }
 
-		Rename_result rename(char const *, char const *) override {
-			return RENAME_ERR_NO_PERM; }
+		Rename_result rename(char const *from, char const *to) override
+		{
+			if (_is_single_file(from) || _is_single_file(to))
+				return RENAME_ERR_NO_PERM;
+			return RENAME_ERR_NO_ENTRY;
+		}
 
 		Mkdir_result mkdir(char const *, unsigned) override {
 			return MKDIR_ERR_NO_PERM; }

repos/os/include/vfs/tar_file_system.h

@@ -528,9 +528,11 @@ class Vfs::Tar_file_system : public File_system
 			return READLINK_OK;
 		}
 
-		Rename_result rename(char const *, char const *) override
+		Rename_result rename(char const *from, char const *to) override
 		{
-			return RENAME_ERR_NO_PERM;
+			if (_root_node.lookup(from) || _root_node.lookup(to))
+				return RENAME_ERR_NO_PERM;
+			return RENAME_ERR_NO_ENTRY;
 		}
 
 		Mkdir_result mkdir(char const *, unsigned) override