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Kernel/FileSystem: Simplify even more the mount syscall

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As with the previous commit, we put a distinction between filesystems
that require a file description and those which don't, but now in a much
more readable mechanism - all initialization properties as well as the
create static method are grouped to create the FileSystemInitializer
structure. Then when we need to initialize an instance, we iterate over
a table of these structures, checking for matching structure and then
validating the given arguments from userspace against the requirements
to ensure we can create a valid instance of the requested filesystem.
This commit is contained in:
Liav A 2022-05-28 15:42:03 +03:00 • committed by Linus Groh
parent 4c588441e3
commit 58acdce41f
17 changed files with 72 additions and 88 deletions
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112
Kernel/Syscalls/mount.cpp
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@ -18,61 +18,52 @@
namespace Kernel {
static ErrorOr<NonnullRefPtr<FileSystem>> create_ram_backed_filesystem_instance(StringView fs_type)
{
RefPtr<FileSystem> fs;
if (fs_type == "proc"sv || fs_type == "ProcFS"sv) {
fs = TRY(ProcFS::try_create());
} else if (fs_type == "devpts"sv || fs_type == "DevPtsFS"sv) {
fs = TRY(DevPtsFS::try_create());
} else if (fs_type == "dev"sv || fs_type == "DevTmpFS"sv) {
fs = TRY(DevTmpFS::try_create());
} else if (fs_type == "sys"sv || fs_type == "SysFS"sv) {
fs = TRY(SysFS::try_create());
} else if (fs_type == "tmp"sv || fs_type == "TmpFS"sv) {
fs = TRY(TmpFS::try_create());
}
if (!fs)
return ENODEV;
return fs.release_nonnull();
}
struct FileSystemInitializer {
StringView short_name;
StringView name;
bool requires_open_file_description { false };
bool requires_block_device { false };
bool requires_seekable_file { false };
ErrorOr<NonnullRefPtr<FileSystem>> (*create_with_fd)(OpenFileDescription&) = nullptr;
ErrorOr<NonnullRefPtr<FileSystem>> (*create)(void) = nullptr;
};
static bool filesystem_mount_require_open_file_description(StringView fs_type)
{
if (fs_type == "ext2"sv || fs_type == "Ext2FS"sv) {
return true;
} else if (fs_type == "9p"sv || fs_type == "Plan9FS"sv) {
return true;
} else if (fs_type == "iso9660"sv || fs_type == "ISO9660FS"sv) {
return true;
}
return false;
}
static constexpr FileSystemInitializer s_initializers[] = {
{ "proc"sv, "ProcFS"sv, false, false, false, {}, ProcFS::try_create },
{ "devpts"sv, "DevPtsFS"sv, false, false, false, {}, DevPtsFS::try_create },
{ "dev"sv, "DevTmpFS"sv, false, false, false, {}, DevTmpFS::try_create },
{ "sys"sv, "SysFS"sv, false, false, false, {}, SysFS::try_create },
{ "tmp"sv, "TmpFS"sv, false, false, false, {}, TmpFS::try_create },
{ "ext2"sv, "Ext2FS"sv, true, true, true, Ext2FS::try_create, {} },
{ "9p"sv, "Plan9FS"sv, true, true, true, Plan9FS::try_create, {} },
{ "iso9660"sv, "ISO9660FS"sv, true, true, true, ISO9660FS::try_create, {} },
};
static ErrorOr<NonnullRefPtr<FileSystem>> create_open_file_description_backed_filesystem_instance(StringView fs_type, OpenFileDescription& description)
static ErrorOr<NonnullRefPtr<FileSystem>> create_filesystem_instance(StringView fs_type, OpenFileDescription* possible_description)
{
RefPtr<FileSystem> fs;
for (auto& initializer_entry : s_initializers) {
if (fs_type != initializer_entry.short_name && fs_type != initializer_entry.name)
continue;
if (!initializer_entry.requires_open_file_description) {
VERIFY(initializer_entry.create);
NonnullRefPtr<FileSystem> fs = TRY(initializer_entry.create());
return fs;
}
VERIFY(initializer_entry.create_with_fd);
if (!possible_description)
return EBADF;
OpenFileDescription& description = *possible_description;
if (fs_type == "ext2"sv || fs_type == "Ext2FS"sv) {
if (!description.file().is_block_device())
if (initializer_entry.requires_block_device && !description.file().is_block_device())
return ENOTBLK;
if (!description.file().is_seekable()) {
if (initializer_entry.requires_seekable_file && !description.file().is_seekable()) {
dbgln("mount: this is not a seekable file");
return ENODEV;
}
fs = TRY(Ext2FS::try_create(description));
} else if (fs_type == "9p"sv || fs_type == "Plan9FS"sv) {
fs = TRY(Plan9FS::try_create(description));
} else if (fs_type == "iso9660"sv || fs_type == "ISO9660FS"sv) {
if (!description.file().is_seekable()) {
dbgln("mount: this is not a seekable file");
return ENODEV;
}
fs = TRY(ISO9660FS::try_create(description));
NonnullRefPtr<FileSystem> fs = TRY(initializer_entry.create_with_fd(description));
return fs;
}
if (!fs)
return ENODEV;
return fs.release_nonnull();
return ENODEV;
}
ErrorOr<FlatPtr> Process::sys$mount(Userspace<Syscall::SC_mount_params const*> user_params)
@ -116,26 +107,19 @@ ErrorOr<FlatPtr> Process::sys$mount(Userspace<Syscall::SC_mount_params const*> u
return 0;
}
// Note: Try to determine as early as possible if we deal with a filesystem type
// that must be backed by a open file description, so if there's no such valid
// description, we can fail with EBADF now.
if (filesystem_mount_require_open_file_description(fs_type) && description_or_error.is_error()) {
return EBADF;
RefPtr<FileSystem> fs;
if (!description_or_error.is_error()) {
auto description = description_or_error.release_value();
fs = TRY(create_filesystem_instance(fs_type, description.ptr()));
auto source_pseudo_path = TRY(description->pseudo_path());
dbgln("mount: attempting to mount {} on {}", source_pseudo_path, target);
} else {
fs = TRY(create_filesystem_instance(fs_type, {}));
}
if (description_or_error.is_error()) {
auto synthetic_filesystem = TRY(create_ram_backed_filesystem_instance(fs_type));
TRY(synthetic_filesystem->initialize());
TRY(VirtualFileSystem::the().mount(*synthetic_filesystem, target_custody, params.flags));
return 0;
}
auto description = description_or_error.release_value();
auto open_file_description_backed_filesystem = TRY(create_open_file_description_backed_filesystem_instance(fs_type, description));
auto source_pseudo_path = TRY(description->pseudo_path());
dbgln("mount: attempting to mount {} on {}", source_pseudo_path, target);
TRY(open_file_description_backed_filesystem->initialize());
TRY(VirtualFileSystem::the().mount(*open_file_description_backed_filesystem, target_custody, params.flags));
TRY(fs->initialize());
TRY(VirtualFileSystem::the().mount(*fs, target_custody, params.flags));
return 0;
}