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23a7ccf607
This is a preparation before we can create a usable mechanism to use filesystem-specific mount flags. To keep some compatibility with userland code, LibC and LibCore mount functions are kept being usable, but now instead of doing an "atomic" syscall, they do multiple syscalls to perform the complete procedure of mounting a filesystem. The FileBackedFileSystem IntrusiveList in the VFS code is now changed to be protected by a Mutex, because when we mount a new filesystem, we need to check if a filesystem is already created for a given source_fd so we do a scan for that OpenFileDescription in that list. If we fail to find an already-created filesystem we create a new one and register it in the list if we successfully mounted it. We use a Mutex because we might need to initiate disk access during the filesystem creation, which will take other mutexes in other parts of the kernel, therefore making it not possible to take a spinlock while doing this.
139 lines
6.9 KiB
C++
139 lines
6.9 KiB
C++
/*
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* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Badge.h>
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#include <AK/Error.h>
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#include <AK/Function.h>
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#include <AK/HashMap.h>
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#include <AK/OwnPtr.h>
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#include <AK/RefPtr.h>
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#include <Kernel/FileSystem/FileBackedFileSystem.h>
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#include <Kernel/FileSystem/FileSystem.h>
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#include <Kernel/FileSystem/Initializer.h>
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#include <Kernel/FileSystem/InodeIdentifier.h>
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#include <Kernel/FileSystem/InodeMetadata.h>
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#include <Kernel/FileSystem/Mount.h>
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#include <Kernel/FileSystem/MountFile.h>
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#include <Kernel/FileSystem/UnveilNode.h>
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#include <Kernel/Forward.h>
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#include <Kernel/Locking/MutexProtected.h>
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#include <Kernel/Locking/SpinlockProtected.h>
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namespace Kernel {
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// Kernel internal options.
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#define O_NOFOLLOW_NOERROR (1 << 29)
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#define O_UNLINK_INTERNAL (1 << 30)
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struct UidAndGid {
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UserID uid;
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GroupID gid;
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};
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enum class AccessFlags {
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None = 0,
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EffectiveAccess = 1 << 0,
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DoNotFollowSymlinks = 1 << 1,
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};
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AK_ENUM_BITWISE_OPERATORS(AccessFlags);
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class VirtualFileSystem {
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public:
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// Required to be at least 8 by POSIX
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// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/limits.h.html
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static constexpr int symlink_recursion_limit = 8;
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static void initialize();
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static VirtualFileSystem& the();
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static ErrorOr<FileSystemInitializer const*> find_filesystem_type_initializer(StringView fs_type);
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VirtualFileSystem();
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~VirtualFileSystem();
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ErrorOr<void> mount_root(FileSystem&);
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ErrorOr<void> mount(MountFile&, OpenFileDescription*, Custody& mount_point, int flags);
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ErrorOr<void> bind_mount(Custody& source, Custody& mount_point, int flags);
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ErrorOr<void> remount(Custody& mount_point, int new_flags);
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ErrorOr<void> unmount(Custody& mount_point);
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ErrorOr<NonnullRefPtr<OpenFileDescription>> open(Credentials const&, StringView path, int options, mode_t mode, Custody& base, Optional<UidAndGid> = {});
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ErrorOr<NonnullRefPtr<OpenFileDescription>> open(Process const&, Credentials const&, StringView path, int options, mode_t mode, Custody& base, Optional<UidAndGid> = {});
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ErrorOr<NonnullRefPtr<OpenFileDescription>> create(Credentials const&, StringView path, int options, mode_t mode, Custody& parent_custody, Optional<UidAndGid> = {});
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ErrorOr<NonnullRefPtr<OpenFileDescription>> create(Process const&, Credentials const&, StringView path, int options, mode_t mode, Custody& parent_custody, Optional<UidAndGid> = {});
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ErrorOr<void> mkdir(Credentials const&, StringView path, mode_t mode, Custody& base);
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ErrorOr<void> link(Credentials const&, StringView old_path, StringView new_path, Custody& base);
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ErrorOr<void> unlink(Credentials const&, StringView path, Custody& base);
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ErrorOr<void> symlink(Credentials const&, StringView target, StringView linkpath, Custody& base);
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ErrorOr<void> rmdir(Credentials const&, StringView path, Custody& base);
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ErrorOr<void> chmod(Credentials const&, StringView path, mode_t, Custody& base, int options = 0);
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ErrorOr<void> chmod(Credentials const&, Custody&, mode_t);
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ErrorOr<void> chown(Credentials const&, StringView path, UserID, GroupID, Custody& base, int options);
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ErrorOr<void> chown(Credentials const&, Custody&, UserID, GroupID);
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ErrorOr<void> access(Credentials const&, StringView path, int mode, Custody& base, AccessFlags);
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ErrorOr<InodeMetadata> lookup_metadata(Credentials const&, StringView path, Custody& base, int options = 0);
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ErrorOr<void> utime(Credentials const&, StringView path, Custody& base, time_t atime, time_t mtime);
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ErrorOr<void> utimensat(Credentials const&, StringView path, Custody& base, timespec const& atime, timespec const& mtime, int options = 0);
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ErrorOr<void> do_utimens(Credentials const& credentials, Custody& custody, timespec const& atime, timespec const& mtime);
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ErrorOr<void> rename(Credentials const&, Custody& old_base, StringView oldpath, Custody& new_base, StringView newpath);
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ErrorOr<void> mknod(Credentials const&, StringView path, mode_t, dev_t, Custody& base);
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ErrorOr<NonnullRefPtr<Custody>> open_directory(Credentials const&, StringView path, Custody& base);
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ErrorOr<void> for_each_mount(Function<ErrorOr<void>(Mount const&)>) const;
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InodeIdentifier root_inode_id() const;
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void sync_filesystems();
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void lock_all_filesystems();
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static void sync();
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NonnullRefPtr<Custody> root_custody();
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ErrorOr<NonnullRefPtr<Custody>> resolve_path(Credentials const&, StringView path, NonnullRefPtr<Custody> base, RefPtr<Custody>* out_parent = nullptr, int options = 0, int symlink_recursion_level = 0);
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ErrorOr<NonnullRefPtr<Custody>> resolve_path(Process const&, Credentials const&, StringView path, NonnullRefPtr<Custody> base, RefPtr<Custody>* out_parent = nullptr, int options = 0, int symlink_recursion_level = 0);
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ErrorOr<NonnullRefPtr<Custody>> resolve_path_without_veil(Credentials const&, StringView path, NonnullRefPtr<Custody> base, RefPtr<Custody>* out_parent = nullptr, int options = 0, int symlink_recursion_level = 0);
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private:
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friend class OpenFileDescription;
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UnveilNode const& find_matching_unveiled_path(Process const&, StringView path);
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ErrorOr<void> validate_path_against_process_veil(Process const&, StringView path, int options);
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ErrorOr<void> validate_path_against_process_veil(Process const& process, Custody const& custody, int options);
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ErrorOr<void> validate_path_against_process_veil(Custody const& path, int options);
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ErrorOr<void> validate_path_against_process_veil(StringView path, int options);
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ErrorOr<void> add_file_system_to_mount_table(FileSystem& file_system, Custody& mount_point, int flags);
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bool is_vfs_root(InodeIdentifier) const;
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ErrorOr<void> traverse_directory_inode(Inode&, Function<ErrorOr<void>(FileSystem::DirectoryEntryView const&)>);
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bool mount_point_exists_at_inode(InodeIdentifier inode);
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// FIXME: These functions are totally unsafe as someone could unmount the returned Mount underneath us.
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Mount* find_mount_for_host(InodeIdentifier);
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Mount* find_mount_for_guest(InodeIdentifier);
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RefPtr<Inode> m_root_inode;
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SpinlockProtected<RefPtr<Custody>, LockRank::None> m_root_custody {};
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SpinlockProtected<IntrusiveList<&Mount::m_vfs_list_node>, LockRank::None> m_mounts {};
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// NOTE: The FileBackedFileSystem list is protected by a mutex because we need to scan it
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// to search for existing filesystems for already used block devices and therefore when doing
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// that we could fail to find a filesystem so we need to create a new filesystem which might
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// need to do disk access (i.e. taking Mutexes in other places) and then register that new filesystem
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// in this list, to avoid TOCTOU bugs.
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MutexProtected<IntrusiveList<&FileBackedFileSystem::m_file_backed_file_system_node>> m_file_backed_file_systems_list {};
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SpinlockProtected<IntrusiveList<&FileSystem::m_file_system_node>, LockRank::FileSystem> m_file_systems_list {};
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};
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}
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