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genode/repos/os/include/vfs/dir_file_system.h
Emery Hemingway 013eb506a8 Vfs::Dir_file_system: do not use Vfs_handle for opening directories as files 
The Dir_file_system uses static cast to convert handles from the
application to a plugin local type. For this reason, only the local
handle type may be returned from 'opendir' or 'open'. This fixes the
unexpected behavior when opening directories as files.

Fix #2533
2018-02-15 10:22:09 +01:00

928 lines
23 KiB
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/*
* \brief Directory file system
* \author Norman Feske
* \author Emery Hemingway
* \author Christian Helmuth
* \date 2012-04-23
*/
/*
* Copyright (C) 2011-2017 Genode Labs GmbH
*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU Affero General Public License version 3.
*/
#ifndef _INCLUDE__VFS__DIR_FILE_SYSTEM_H_
#define _INCLUDE__VFS__DIR_FILE_SYSTEM_H_
#include <base/registry.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 };
struct Root { };
private:
/*
* Noncopyable
*/
Dir_file_system(Dir_file_system const &);
Dir_file_system &operator = (Dir_file_system const &);
/**
* This instance is the root of VFS
*
* Additionally, the root has an empty _name.
*/
bool _vfs_root;
struct Dir_vfs_handle : Vfs_handle
{
struct Subdir_handle_element;
typedef Genode::Registry<Subdir_handle_element> Subdir_handle_registry;
struct Subdir_handle_element : Subdir_handle_registry::Element
{
bool synced { false };
Vfs_handle &vfs_handle;
Subdir_handle_element(Subdir_handle_registry &registry,
Vfs_handle &vfs_handle)
: Subdir_handle_registry::Element(registry, *this),
vfs_handle(vfs_handle) { }
};
Absolute_path path;
Vfs_handle *queued_read_handle { nullptr };
Subdir_handle_registry subdir_handle_registry { };
Dir_vfs_handle(Directory_service &ds,
File_io_service &fs,
Genode::Allocator &alloc,
char const *path)
: Vfs_handle(ds, fs, alloc, 0),
path(path) { }
~Dir_vfs_handle()
{
/* close all sub-handles */
auto f = [&] (Subdir_handle_element &e) {
e.vfs_handle.ds().close(&e.vfs_handle);
destroy(alloc(), &e);
};
subdir_handle_registry.for_each(f);
}
private:
/*
* Noncopyable
*/
Dir_vfs_handle(Dir_vfs_handle const &);
Dir_vfs_handle &operator = (Dir_vfs_handle const &);
};
/* 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];
/**
* Returns if path corresponds to top directory of file system
*/
bool _top_dir(char const *path) const { return strcmp(path, "/") == 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 (_vfs_root)
return path;
if (_top_dir(path))
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;
}
/*
* 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;
}
bool _queue_read_of_file_systems(Dir_vfs_handle *dir_vfs_handle)
{
bool result = true;
dir_vfs_handle->queued_read_handle = nullptr;
file_offset index = dir_vfs_handle->seek() / sizeof(Dirent);
char const *sub_path = _sub_path(dir_vfs_handle->path.base());
if (strlen(sub_path) == 0)
sub_path = "/";
/* base of composite directory index */
int base = 0;
auto f = [&] (Dir_vfs_handle::Subdir_handle_element &handle_element) {
if (dir_vfs_handle->queued_read_handle) return; /* skip through */
Vfs_handle &vfs_handle = handle_element.vfs_handle;
/*
* Determine number of matching directory entries within
* the current file system.
*/
int const fs_num_dirent = vfs_handle.ds().num_dirent(sub_path);
/*
* Query directory entry if index lies with the file
* system.
*/
if (index - base < fs_num_dirent) {
/* set this handle to be used for read completion */
dir_vfs_handle->queued_read_handle = &vfs_handle;
/* seek to file-system local index */
index = index - base;
vfs_handle.seek(index * sizeof(Dirent));
/* forward the handle context */
vfs_handle.context = dir_vfs_handle->context;
result = vfs_handle.fs().queue_read(&vfs_handle, sizeof(Dirent));
}
/* adjust base index for next file system */
base += fs_num_dirent;
};
dir_vfs_handle->subdir_handle_registry.for_each(f);
return result;
}
Read_result _complete_read_of_file_systems(Dir_vfs_handle *dir_vfs_handle,
char *dst, file_size count,
file_size &out_count)
{
if (!dir_vfs_handle->queued_read_handle) {
/*
* no fs was found for the given index or
* fs->opendir() failed
*/
if (count < sizeof(Dirent))
return READ_ERR_INVALID;
Dirent *dirent = (Dirent*)dst;
*dirent = Dirent();
out_count = sizeof(Dirent);
return READ_OK;
}
Read_result result = dir_vfs_handle->queued_read_handle->fs().
complete_read(dir_vfs_handle->queued_read_handle,
dst, count, out_count);
if (result == READ_QUEUED)
return result;
dir_vfs_handle->queued_read_handle = nullptr;
return result;
}
public:
Dir_file_system(Genode::Env &env,
Genode::Allocator &alloc,
Genode::Xml_node node,
Io_response_handler &io_handler,
File_system_factory &fs_factory)
:
_vfs_root(false),
_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 (alloc)
Dir_file_system(env, alloc, sub_node, io_handler, fs_factory));
continue;
}
File_system *fs = fs_factory.create(env, alloc, sub_node, io_handler);
if (fs) {
_append_file_system(fs);
continue;
}
Genode::error("failed to create <", sub_node.type(), "> VFS node");
try {
String<64> value;
for (unsigned i = 0; i < 16; ++i) {
Xml_attribute attr = sub_node.attribute(i);
attr.value(&value);
Genode::error("\t", attr.name(), "=\"", value, "\"");
}
} catch (Xml_node::Nonexistent_attribute) { }
}
}
Dir_file_system(Genode::Env &env,
Genode::Allocator &alloc,
Genode::Xml_node node,
Io_response_handler &io_handler,
File_system_factory &fs_factory,
Dir_file_system::Root)
:
Dir_file_system(env, alloc, node, io_handler, fs_factory)
{ _vfs_root = true; }
/*********************************
** 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 || _top_dir(path)) {
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;
}
file_size num_dirent(char const *path) override
{
if (_vfs_root) {
return _sum_dirents_of_file_systems(path);
} else {
if (_top_dir(path))
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;
}
}
/**
* Return true if specified path is a directory
*/
bool directory(char const *path) override
{
if (_top_dir(path))
return true;
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->directory(path))
return true;
return false;
}
/**
* Return true if specified path is a directory
*
* \noapi
* \deprecated use 'directory instead
*/
bool is_directory(char const *path) { return directory(path); }
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) 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 (directory(path)) {
try {
*out_handle = new (alloc) Dir_vfs_handle(*this, *this, alloc, path);
return OPEN_OK;
}
catch (Genode::Out_of_ram) { return OPEN_ERR_OUT_OF_RAM; }
catch (Genode::Out_of_caps) { return OPEN_ERR_OUT_OF_CAPS; }
}
/*
* 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) {
try {
*out_handle = new (alloc) Vfs_handle(*this, *this, alloc, 0);
return OPEN_OK;
}
catch (Genode::Out_of_ram) { return OPEN_ERR_OUT_OF_RAM; }
catch (Genode::Out_of_caps) { return OPEN_ERR_OUT_OF_CAPS; }
}
/* 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;
}
/**
* Call 'opendir()' on each file system and store handles in
* a registry.
*/
Opendir_result open_composite_dirs(char const *sub_path,
Dir_vfs_handle &dir_vfs_handle)
{
try {
for (File_system *fs = _first_file_system; fs; fs = fs->next) {
Vfs_handle *sub_dir_handle = nullptr;
Opendir_result r = fs->opendir(
sub_path, false, &sub_dir_handle, dir_vfs_handle.alloc());
switch (r) {
case OPENDIR_OK:
break;
case OPEN_ERR_OUT_OF_RAM:
case OPEN_ERR_OUT_OF_CAPS:
return r;
case OPENDIR_ERR_LOOKUP_FAILED:
default:
continue;
}
new (dir_vfs_handle.alloc())
Dir_vfs_handle::Subdir_handle_element(
dir_vfs_handle.subdir_handle_registry, *sub_dir_handle);
}
}
catch (Genode::Out_of_ram) { return OPENDIR_ERR_OUT_OF_RAM; }
catch (Genode::Out_of_caps) { return OPENDIR_ERR_OUT_OF_CAPS; }
return OPENDIR_OK;
}
Opendir_result opendir(char const *path, bool create,
Vfs_handle **out_handle, Allocator &alloc) override
{
Opendir_result result = OPENDIR_OK;
if (_top_dir(path)) {
if (create)
return OPENDIR_ERR_PERMISSION_DENIED;
/*
* opendir with '/' (called from 'open_composite_dirs' returns handle
* only, VFS root additionally calls 'open_composite_dirs' in order to
* open its file systems
*/
Dir_vfs_handle *root_handle;
try {
root_handle = new (alloc)
Dir_vfs_handle(*this, *this, alloc, path);
}
catch (Genode::Out_of_ram) { return OPENDIR_ERR_OUT_OF_RAM; }
catch (Genode::Out_of_caps) { return OPENDIR_ERR_OUT_OF_CAPS; }
/* the VFS root may contain more file systems */
if (_vfs_root)
result = open_composite_dirs("/", *root_handle);
if (result == OPENDIR_OK) {
*out_handle = root_handle;
} else {
/* close the root handle and the rest will follow */
close(root_handle);
}
return result;
}
char const *sub_path = _sub_path(path);
if (!sub_path)
return OPENDIR_ERR_LOOKUP_FAILED;
if (create) {
auto opendir_fn = [&] (File_system &fs, char const *path)
{
Vfs_handle *tmp_handle;
Opendir_result opendir_result =
fs.opendir(path, true, &tmp_handle, alloc);
if (opendir_result == OPENDIR_OK)
fs.close(tmp_handle);
return opendir_result; /* return from lambda */
};
Opendir_result opendir_result =
_dir_op(OPENDIR_ERR_LOOKUP_FAILED,
OPENDIR_ERR_PERMISSION_DENIED,
OPENDIR_OK,
path, opendir_fn);
if (opendir_result != OPENDIR_OK)
return opendir_result;
}
Dir_vfs_handle *dir_vfs_handle;
try {
dir_vfs_handle = new (alloc)
Dir_vfs_handle(*this, *this, alloc, path);
}
catch (Genode::Out_of_ram) { return OPENDIR_ERR_OUT_OF_RAM; }
catch (Genode::Out_of_caps) { return OPENDIR_ERR_OUT_OF_CAPS; }
/* path equals "/" (for reading the name of this directory) */
if (strlen(sub_path) == 0)
sub_path = "/";
result = open_composite_dirs(sub_path, *dir_vfs_handle);
if (result == OPENDIR_OK) {
*out_handle = dir_vfs_handle;
} else {
/* close the master handle and the rest will follow */
close(dir_vfs_handle);
}
return result;
}
Openlink_result openlink(char const *path, bool create,
Vfs_handle **out_handle,
Allocator &alloc) override
{
auto openlink_fn = [&] (File_system &fs, char const *path)
{
return fs.openlink(path, create, out_handle, alloc);
};
return _dir_op(OPENLINK_ERR_LOOKUP_FAILED,
OPENLINK_ERR_PERMISSION_DENIED,
OPENLINK_OK,
path, openlink_fn);
}
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);
}
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;
}
/***************************
** File_system interface **
***************************/
char const *name() const { return "dir"; }
char const *type() override { return "dir"; }
void apply_config(Genode::Xml_node const &node) override
{
using namespace Genode;
File_system *curr = _first_file_system;
for (unsigned i = 0; i < node.num_sub_nodes(); i++, curr = curr->next) {
Xml_node const &sub_node = node.sub_node(i);
/* check if type of XML node matches current file-system type */
if (sub_node.has_type(curr->type()) == false) {
Genode::error("VFS config update failed (node type '",
sub_node.type(), "' != fs type '", curr->type(),"')");
return;
}
curr->apply_config(node.sub_node(i));
}
}
/********************************
** File I/O service interface **
********************************/
Write_result write(Vfs_handle *, char const *, file_size, file_size &) override
{
return WRITE_ERR_INVALID;
}
bool queue_read(Vfs_handle *vfs_handle, file_size) override
{
Dir_vfs_handle *dir_vfs_handle =
static_cast<Dir_vfs_handle*>(vfs_handle);
if (_vfs_root)
return _queue_read_of_file_systems(dir_vfs_handle);
if (_top_dir(dir_vfs_handle->path.base()))
return true;
return _queue_read_of_file_systems(dir_vfs_handle);
}
Read_result complete_read(Vfs_handle *vfs_handle,
char *dst, file_size count,
file_size &out_count) override
{
out_count = 0;
if (count < sizeof(Dirent))
return READ_ERR_INVALID;
Dir_vfs_handle *dir_vfs_handle =
static_cast<Dir_vfs_handle*>(vfs_handle);
if (_vfs_root)
return _complete_read_of_file_systems(dir_vfs_handle, dst, count, out_count);
if (_top_dir(dir_vfs_handle->path.base())) {
Dirent *dirent = (Dirent*)dst;
file_offset index = vfs_handle->seek() / sizeof(Dirent);
if (index == 0) {
strncpy(dirent->name, _name, sizeof(dirent->name));
dirent->type = DIRENT_TYPE_DIRECTORY;
dirent->fileno = 1;
} else {
dirent->type = DIRENT_TYPE_END;
}
out_count = sizeof(Dirent);
return READ_OK;
}
return _complete_read_of_file_systems(dir_vfs_handle, dst, count, out_count);
}
Ftruncate_result ftruncate(Vfs_handle *, file_size) override
{
return FTRUNCATE_ERR_NO_PERM;
}
bool read_ready(Vfs_handle *handle) override
{
if (&handle->fs() == this)
return true;
return handle->fs().read_ready(handle);
}
bool notify_read_ready(Vfs_handle *handle) override
{
if (&handle->fs() == this)
return true;
return handle->fs().notify_read_ready(handle);
}
bool queue_sync(Vfs_handle *vfs_handle) override
{
bool result = true;
Dir_vfs_handle *dir_vfs_handle =
static_cast<Dir_vfs_handle*>(vfs_handle);
auto f = [&result, dir_vfs_handle] (Dir_vfs_handle::Subdir_handle_element &e) {
/* forward the handle context */
e.vfs_handle.context = dir_vfs_handle->context;
e.synced = false;
if (!e.vfs_handle.fs().queue_sync(&e.vfs_handle)) {
result = false;
}
};
dir_vfs_handle->subdir_handle_registry.for_each(f);
return result;
}
Sync_result complete_sync(Vfs_handle *vfs_handle) override
{
Sync_result result = SYNC_OK;
Dir_vfs_handle *dir_vfs_handle =
static_cast<Dir_vfs_handle*>(vfs_handle);
auto f = [&result, dir_vfs_handle] (Dir_vfs_handle::Subdir_handle_element &e) {
if (e.synced)
return;
Sync_result r = e.vfs_handle.fs().complete_sync(&e.vfs_handle);
if (r != SYNC_OK)
result = r;
else
e.synced = true;
};
dir_vfs_handle->subdir_handle_registry.for_each(f);
return result;
}
};
#endif /* _INCLUDE__VFS__DIR_FILE_SYSTEM_H_ */
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