/*
* \brief Directory file system
* \author Norman Feske
* \date 2012-04-23
*/
/*
* Copyright (C) 2011-2016 Genode Labs GmbH
*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU General Public License version 2.
*/
#ifndef _INCLUDE__VFS__DIR_FILE_SYSTEM_H_
#define _INCLUDE__VFS__DIR_FILE_SYSTEM_H_
#include <vfs/file_system_factory.h>
#include <vfs/vfs_handle.h>
namespace Vfs { class Dir_file_system; }
class Vfs::Dir_file_system : public File_system
{
public:
enum { MAX_NAME_LEN = 128 };
private:
/* pointer to first child file system */
File_system *_first_file_system;
/* add new file system to the list of children */
void _append_file_system(File_system *fs)
{
if (!_first_file_system) {
_first_file_system = fs;
return;
}
File_system *curr = _first_file_system;
while (curr->next)
curr = curr->next;
curr->next = fs;
}
/**
* Directory name
*/
char _name[MAX_NAME_LEN];
bool _is_root() const { return _name[0] == 0; }
/**
* Perform operation on a file system
*
* \param fn functor that takes a file-system reference and
* the path as arguments
*/
template <typename RES, typename FN>
RES _dir_op(RES const no_entry, RES const no_perm, RES const ok,
char const *path, FN const &fn)
{
path = _sub_path(path);
/* path does not match directory name */
if (!path)
return no_entry;
/*
* Prevent operation if path equals directory name defined
* via the static VFS configuration.
*/
if (strlen(path) == 0)
return no_perm;
/*
* If any of the sub file systems returns a permission error and
* there exists no sub file system that takes the request, we
* return the permission error.
*/
bool permission_denied = false;
/*
* Keep the most meaningful error code. When using stacked file
* systems, most child file systems will eventually return no
* entry (or leave the error code unchanged). If any of those
* file systems has anything more interesting to tell, return
* this information after all file systems have been tried and
* none could handle the request.
*/
RES error = ok;
/*
* The given path refers to at least one of our sub directories.
* Propagate the request into all of our file systems. If at least
* one operation succeeds, we return success.
*/
for (File_system *fs = _first_file_system; fs; fs = fs->next) {
RES const err = fn(*fs, path);
if (err == ok)
return err;
if (err != no_entry && err != no_perm) {
error = err;
}
if (err == no_perm)
permission_denied = true;
}
/* none of our file systems could successfully operate on the path */
return error != ok ? error : permission_denied ? no_perm : no_entry;
}
/**
* Return portion of the path after the element corresponding to
* the current directory.
*/
char const *_sub_path(char const *path) const
{
/* do not strip anything from the path when we are root */
if (_is_root())
return path;
/* skip heading slash in path if present */
if (path[0] == '/')
path++;
Genode::size_t const name_len = strlen(_name);
if (strcmp(path, _name, name_len) != 0)
return 0;
path += name_len;
/*
* The first characters of the first path element are equal to
* the current directory name. Let's check if the length of the
* first path element matches the name length.
*/
if (*path != 0 && *path != '/')
return 0;
return path;
}
/**
* The 'path' is relative to the child file systems.
*/
Dirent_result _dirent_of_file_systems(char const *path, file_offset index, Dirent &out)
{
int base = 0;
for (File_system *fs = _first_file_system; fs; fs = fs->next) {
/*
* Determine number of matching directory entries within
* the current file system.
*/
int const fs_num_dirent = fs->num_dirent(path);
/*
* Query directory entry if index lies with the file
* system.
*/
if (index - base < fs_num_dirent) {
index = index - base;
return fs->dirent(path, index, out);;
}
/* adjust base index for next file system */
base += fs_num_dirent;
}
out.type = DIRENT_TYPE_END;
return DIRENT_OK;
}
void _dirent_of_this_dir_node(file_offset index, Dirent &out)
{
if (index == 0) {
strncpy(out.name, _name, sizeof(out.name));
out.type = DIRENT_TYPE_DIRECTORY;
out.fileno = 1;
} else {
out.type = DIRENT_TYPE_END;
}
}
/*
* Accumulate number of directory entries that match in any of
* our sub file systems.
*/
file_size _sum_dirents_of_file_systems(char const *path)
{
file_size cnt = 0;
for (File_system *fs = _first_file_system; fs; fs = fs->next) {
cnt += fs->num_dirent(path);
}
return cnt;
}
public:
Dir_file_system(Xml_node node, File_system_factory &fs_factory)
:
_first_file_system(0)
{
using namespace Genode;
/* remember directory name */
if (node.has_type("fstab") || node.has_type("vfs"))
_name[0] = 0;
else
node.attribute("name").value(_name, sizeof(_name));
for (unsigned i = 0; i < node.num_sub_nodes(); i++) {
Xml_node sub_node = node.sub_node(i);
/* traverse into <dir> nodes */
if (sub_node.has_type("dir")) {
_append_file_system(new (env()->heap())
Dir_file_system(sub_node, fs_factory));
continue;
}
File_system *fs = fs_factory.create(sub_node);
if (fs) {
_append_file_system(fs);
continue;
}
PERR("failed to create <%s> VFS node", sub_node.type().string());
try {
String<64> value;
for (unsigned i = 0; i < 16; ++i) {
Xml_attribute attr = sub_node.attribute(i);
attr.value(&value);
PERR("\t%s=\"%s\"", attr.name().string(), value.string());
}
} catch (Xml_node::Nonexistent_attribute) { }
}
}
/*********************************
** Directory-service interface **
*********************************/
Dataspace_capability dataspace(char const *path) override
{
path = _sub_path(path);
if (!path)
return Dataspace_capability();
/*
* Query sub file systems for dataspace using the path local to
* the respective file system
*/
File_system *fs = _first_file_system;
for (; fs; fs = fs->next) {
Dataspace_capability ds = fs->dataspace(path);
if (ds.valid())
return ds;
}
return Dataspace_capability();
}
void release(char const *path, Dataspace_capability ds_cap) override
{
path = _sub_path(path);
if (!path)
return;
for (File_system *fs = _first_file_system; fs; fs = fs->next)
fs->release(path, ds_cap);
}
Stat_result stat(char const *path, Stat &out) override
{
path = _sub_path(path);
/* path does not match directory name */
if (!path)
return STAT_ERR_NO_ENTRY;
/*
* If path equals directory name, return information about the
* current directory.
*/
if (strlen(path) == 0 || (strcmp(path, "/") == 0)) {
out.size = 0;
out.mode = STAT_MODE_DIRECTORY | 0755;
out.uid = 0;
out.gid = 0;
out.inode = 1;
out.device = (Genode::addr_t)this;
return STAT_OK;
}
/*
* The given path refers to one of our sub directories.
* Propagate the request into our file systems.
*/
for (File_system *fs = _first_file_system; fs; fs = fs->next) {
Stat_result const err = fs->stat(path, out);
if (err == STAT_OK)
return err;
if (err != STAT_ERR_NO_ENTRY)
return err;
}
/* none of our file systems felt responsible for the path */
return STAT_ERR_NO_ENTRY;
}
Dirent_result dirent(char const *path, file_offset index, Dirent &out) override
{
if (_is_root())
return _dirent_of_file_systems(path, index, out);
if (strcmp(path, "/") == 0) {
_dirent_of_this_dir_node(index, out);
return DIRENT_OK;
}
/* path contains at least one element */
/* remove current element from path */
path = _sub_path(path);
/* path does not lie within our tree */
if (!path)
return DIRENT_ERR_INVALID_PATH;
return _dirent_of_file_systems(*path ? path : "/", index, out);
}
file_size num_dirent(char const *path) override
{
if (_is_root()) {
return _sum_dirents_of_file_systems(path);
} else {
if (strcmp(path, "/") == 0)
return 1;
/*
* The path contains at least one element. Remove current
* element from path.
*/
path = _sub_path(path);
/*
* If the resulting 'path' is non-null, the path lies
* within our tree. In this case, determine the sum of
* matching dirents of all our file systems. Otherwise,
* the specified path lies outside our directory node.
*/
return path ? _sum_dirents_of_file_systems(*path ? path : "/") : 0;
}
}
bool is_directory(char const *path) override
{
path = _sub_path(path);
if (!path)
return false;
if (strlen(path) == 0)
return true;
for (File_system *fs = _first_file_system; fs; fs = fs->next)
if (fs->is_directory(path))
return true;
return false;
}
char const *leaf_path(char const *path) override
{
path = _sub_path(path);
if (!path)
return 0;
if (strlen(path) == 0)
return path;
for (File_system *fs = _first_file_system; fs; fs = fs->next) {
char const *leaf_path = fs->leaf_path(path);
if (leaf_path)
return leaf_path;
}
return 0;
}
Open_result open(char const *path,
unsigned mode,
Vfs_handle **out_handle,
Allocator &alloc = *Genode::env()->heap()) override
{
/*
* If 'path' is a directory, we create a 'Vfs_handle'
* for the root directory so that subsequent 'dirent' calls
* are subjected to the stacked file-system layout.
*/
if (is_directory(path)) {
*out_handle = new (alloc) Vfs_handle(*this, *this, alloc, 0);
return OPEN_OK;
}
/*
* If 'path' refers to a non-directory node, create a
* 'Vfs_handle' local to the file system that provides the
* file.
*/
path = _sub_path(path);
/* check if path does not match directory name */
if (!path)
return OPEN_ERR_UNACCESSIBLE;
/* path equals directory name */
if (strlen(path) == 0) {
*out_handle = new (alloc) Vfs_handle(*this, *this, alloc, 0);
return OPEN_OK;
}
/* path refers to any of our sub file systems */
for (File_system *fs = _first_file_system; fs; fs = fs->next) {
Open_result const err = fs->open(path, mode, out_handle, alloc);
switch (err) {
case OPEN_ERR_UNACCESSIBLE:
continue;
default:
return err;
}
}
/* path does not match any existing file or directory */
return OPEN_ERR_UNACCESSIBLE;
}
void close(Vfs_handle *handle) override
{
if (handle && (&handle->ds() == this))
destroy(handle->alloc(), handle);
}
Unlink_result unlink(char const *path) override
{
auto unlink_fn = [] (File_system &fs, char const *path)
{
return fs.unlink(path);
};
return _dir_op(UNLINK_ERR_NO_ENTRY, UNLINK_ERR_NO_PERM, UNLINK_OK,
path, unlink_fn);
}
Readlink_result readlink(char const *path, char *buf, file_size buf_size,
file_size &out_len) override
{
auto readlink_fn = [&] (File_system &fs, char const *path)
{
return fs.readlink(path, buf, buf_size, out_len);
};
return _dir_op(READLINK_ERR_NO_ENTRY, READLINK_ERR_NO_ENTRY, READLINK_OK,
path, readlink_fn);
}
Rename_result rename(char const *from_path, char const *to_path) override
{
from_path = _sub_path(from_path);
to_path = _sub_path(to_path);
/* path does not match directory name */
if (!from_path)
return RENAME_ERR_NO_ENTRY;
/*
* Cannot rename a path in the static VFS configuration.
*/
if (strlen(from_path) == 0)
return RENAME_ERR_NO_PERM;
/*
* Check if destination path resides within the same file
* system instance as the source path.
*/
if (!to_path)
return RENAME_ERR_CROSS_FS;
Rename_result final = RENAME_ERR_NO_ENTRY;
for (File_system *fs = _first_file_system; fs; fs = fs->next) {
switch (fs->rename(from_path, to_path)) {
case RENAME_OK: return RENAME_OK;
case RENAME_ERR_NO_ENTRY: continue;
case RENAME_ERR_NO_PERM: return RENAME_ERR_NO_PERM;
case RENAME_ERR_CROSS_FS: final = RENAME_ERR_CROSS_FS;
}
}
return final;
}
Symlink_result symlink(char const *from, char const *to) override
{
auto symlink_fn = [&] (File_system &fs, char const *to)
{
return fs.symlink(from, to);
};
return _dir_op(SYMLINK_ERR_NO_ENTRY, SYMLINK_ERR_NO_PERM, SYMLINK_OK,
to, symlink_fn);
}
Mkdir_result mkdir(char const *path, unsigned mode) override
{
auto mkdir_fn = [&] (File_system &fs, char const *path)
{
return fs.mkdir(path, mode);
};
return _dir_op(MKDIR_ERR_NO_ENTRY, MKDIR_ERR_NO_PERM, MKDIR_OK,
path, mkdir_fn);
}
/***************************
** File_system interface **
***************************/
char const *name() const { return "dir"; }
/**
* Synchronize all file systems
*/
void sync(char const *path) override
{
if (strcmp("/", path, 2) == 0) {
for (File_system *fs = _first_file_system; fs; fs = fs->next)
fs->sync("/");
return;
}
path = _sub_path(path);
if (!path)
return;
for (File_system *fs = _first_file_system; fs; fs = fs->next)
fs->sync(path);
}
/********************************
** File I/O service interface **
********************************/
Write_result write(Vfs_handle *handle, char const *, file_size,
file_size &) override
{
return WRITE_ERR_INVALID;
}
Read_result read(Vfs_handle *, char *, file_size, file_size &) override
{
return READ_ERR_INVALID;
}
Ftruncate_result ftruncate(Vfs_handle *, file_size) override
{
return FTRUNCATE_ERR_NO_PERM;
}
};
#endif /* _INCLUDE__VFS__DIR_FILE_SYSTEM_H_ */