diff options
Diffstat (limited to 'kernel/src/filesystem/ext2/filesystem.cpp')
| -rw-r--r-- | kernel/src/filesystem/ext2/filesystem.cpp | 247 |
1 files changed, 247 insertions, 0 deletions
diff --git a/kernel/src/filesystem/ext2/filesystem.cpp b/kernel/src/filesystem/ext2/filesystem.cpp new file mode 100644 index 0000000..3180a19 --- /dev/null +++ b/kernel/src/filesystem/ext2/filesystem.cpp @@ -0,0 +1,247 @@ +#include <kernel/filesystem/ext2/filesystem.hpp> + +#include <kernel/filesystem/ext2/block_group_descriptor.hpp> +#include <kernel/filesystem/ext2/inode.hpp> +#include <kernel/filesystem/ext2/linked_directory_entry.hpp> +#include <kernel/filesystem/ext2/superblock.hpp> +#include <kernel/filesystem/filesystem.hpp> +#include <kernel/filesystem/inode.hpp> +#include <kernel/filesystem/type.hpp> + +#include <kstd/memory> +#include <kstd/unikstd.h> +#include <kstd/vector> + +#include <array> +#include <cstddef> +#include <cstdint> +#include <string_view> + +namespace kernel::filesystem::ext2 +{ + + struct type final : kernel::filesystem::type + { + [[nodiscard]] auto name() const noexcept -> std::string_view override + { + return "ext2"; + } + + [[nodiscard]] auto requires_device() const noexcept -> bool override + { + return true; + } + + [[nodiscard]] auto make_instance() const -> kstd::shared_ptr<kernel::filesystem::filesystem> override + { + return kstd::make_shared<filesystem>(); + } + }; + + [[gnu::used]] + constexpr auto registration = type_registration<type>{}; + + auto filesystem::mount(kstd::shared_ptr<kernel::filesystem::inode> const & backing_inode) -> operation_result + { + kernel::filesystem::filesystem::mount(backing_inode); + + m_backing_inode->read(&m_superblock, constants::superblock_offset, sizeof(m_superblock)); + + if (m_superblock.magic != constants::magic_number) + { + return operation_result::invalid_magic_number; + } + + auto const blocks_per_group = m_superblock.blocks_per_group; + auto const num_block_groups = (m_superblock.blocks_count + blocks_per_group - 1) / blocks_per_group; + + m_block_group_descriptors = kstd::vector<block_group_descriptor>(num_block_groups); + + m_backing_inode->read(m_block_group_descriptors.data(), block_group_descriptor_table_offset(), + num_block_groups * sizeof(block_group_descriptor)); + + m_root_inode = read_inode(constants::root_inode_number); + + if (!m_root_inode || !m_root_inode->is_directory()) + { + return operation_result::invalid_root_inode; + } + return operation_result::success; + } + + auto filesystem::lookup(kstd::shared_ptr<kernel::filesystem::inode> const & parent, std::string_view name) const + -> kstd::shared_ptr<kernel::filesystem::inode> + { + if (!parent || !parent->is_directory()) + { + return nullptr; + } + + auto * ext2_parent = static_cast<inode *>(parent.get()); + if (!ext2_parent) + { + return nullptr; + } + + auto const & inode_data = ext2_parent->data(); + kstd::vector<uint8_t> buffer(block_size()); + + for (uint32_t i = 0; i < inode_block_count(inode_data); ++i) + { + auto const global_block_number = map_inode_block_index_to_global_block_number(i, inode_data); + auto const block_offset = global_block_number * block_size(); + m_backing_inode->read(buffer.data(), block_offset, block_size()); + + auto const * entry = reinterpret_cast<linked_directory_entry const *>(buffer.data()); + auto bytes_read = 0uz; + + while (bytes_read < block_size() && entry->inode != 0) + { + auto const entry_name = std::string_view{entry->name.data(), entry->name_len}; + if (entry_name == name) + { + return read_inode(entry->inode); + } + + bytes_read += entry->rec_len; + entry = reinterpret_cast<linked_directory_entry const *>(buffer.data() + bytes_read); + } + } + + return nullptr; + } + + auto filesystem::read_inode(uint32_t inode_number) const -> kstd::shared_ptr<inode> + { + auto const inodes_per_group = m_superblock.inodes_per_group; + auto const block_group_index = (inode_number - 1) / inodes_per_group; + auto const inode_index_within_group = (inode_number - 1) % inodes_per_group; + + if (block_group_index >= m_block_group_descriptors.size()) + { + return nullptr; + } + + auto const & block_group_descriptor = m_block_group_descriptors.at(block_group_index); + auto const inode_table_start_block = block_group_descriptor.inode_table; + auto const inode_table_offset = static_cast<size_t>(inode_table_start_block) * block_size(); + auto const inode_offset = inode_table_offset + inode_index_within_group * inode_size(); + + auto new_inode_data = inode_data{}; + m_backing_inode->read(&new_inode_data, inode_offset, sizeof(inode_data)); + + return kstd::make_shared<inode>(this, new_inode_data); + } + + auto filesystem::indirect_levels() const -> std::array<indirect_level, 3> + { + return { + {{constants::singly_indirect_block_index, block_numbers_per_singly_indirect_block()}, + {constants::doubly_indirect_block_index, block_numbers_per_doubly_indirect_block()}, + {constants::triply_indirect_block_index, block_numbers_per_triply_indirect_block()}} + }; + } + + auto filesystem::map_inode_block_index_to_global_block_number(size_t inode_block_index, inode_data data) const + -> kstd::ssize_t + { + if (inode_block_index < constants::direct_block_count) + { + return data.block.at(inode_block_index); + } + + inode_block_index -= constants::direct_block_count; + + for (auto const & level : indirect_levels()) + { + if (inode_block_index >= level.capacity) + { + inode_block_index -= level.capacity; + continue; + } + + auto block_number = data.block[level.slot_index]; + if (block_number == 0) + { + return 0; + } + + for (auto stride = level.capacity / block_numbers_per_block();; stride /= block_numbers_per_block()) + { + auto const idx = inode_block_index / stride; + inode_block_index %= stride; + + block_number = read_block_number_at_index(block_number, idx); + if (block_number == 0) + { + return 0; + } + + if (stride == 1) + { + break; + } + } + + return block_number; + } + + return -1; + } + + auto filesystem::read_block_number_at_index(uint32_t block_number, size_t index) const -> uint32_t + { + uint32_t block_number_buffer = 0; + + auto const block_start_offset = block_number * block_size(); + auto const number_start_address = block_start_offset + index * sizeof(uint32_t); + m_backing_inode->read(&block_number_buffer, number_start_address, sizeof(uint32_t)); + + return block_number_buffer; + } + + auto filesystem::block_numbers_per_block() const -> size_t + { + return block_size() / sizeof(uint32_t); + } + + auto filesystem::block_numbers_per_singly_indirect_block() const -> size_t + { + return block_numbers_per_block(); + } + + auto filesystem::block_numbers_per_doubly_indirect_block() const -> size_t + { + return block_numbers_per_singly_indirect_block() * block_numbers_per_block(); + } + + auto filesystem::block_numbers_per_triply_indirect_block() const -> size_t + { + return block_numbers_per_doubly_indirect_block() * block_numbers_per_block(); + } + + auto filesystem::block_size() const -> size_t + { + return constants::base_block_size << m_superblock.log_block_size; + } + + auto filesystem::revision_level() const -> uint32_t + { + return m_superblock.rev_level; + } + + auto filesystem::inode_size() const -> uint16_t + { + return revision_level() == constants::good_old_revision ? 128 : m_superblock.inode_size; + } + + auto filesystem::inode_block_count(inode_data const & data) const -> uint32_t + { + return data.blocks / (2 << m_superblock.log_block_size); + } + + auto filesystem::block_group_descriptor_table_offset() const -> size_t + { + return block_size() == 1024 ? 2 * block_size() : block_size(); + } +} // namespace kernel::filesystem::ext2 |