diff options
| -rw-r--r-- | arch/x86_64/include/arch/memory/multiboot.hpp | 4 | ||||
| -rw-r--r-- | arch/x86_64/include/arch/memory/paging.hpp | 43 | ||||
| -rw-r--r-- | arch/x86_64/src/memory/paging.cpp | 47 |
3 files changed, 64 insertions, 30 deletions
diff --git a/arch/x86_64/include/arch/memory/multiboot.hpp b/arch/x86_64/include/arch/memory/multiboot.hpp index 9a753fa..9cca8bc 100644 --- a/arch/x86_64/include/arch/memory/multiboot.hpp +++ b/arch/x86_64/include/arch/memory/multiboot.hpp @@ -194,7 +194,9 @@ namespace teachos::arch::memory auto operator==(elf_section_flags const & other) const -> bool = default; private: - std::bitset<64U> flags; + std::bitset<64U> flags; ///< Underlying bitset used to read the flags from. Bits 21 - 28 are reserved for operating + ///< system specific semantics and bits 29 - 32 are reserved for processor specific + ///< semantics. Bits 33 - 64 are unused for compatability with ELF32. }; /** diff --git a/arch/x86_64/include/arch/memory/paging.hpp b/arch/x86_64/include/arch/memory/paging.hpp index 4092d18..d55835e 100644 --- a/arch/x86_64/include/arch/memory/paging.hpp +++ b/arch/x86_64/include/arch/memory/paging.hpp @@ -111,40 +111,53 @@ namespace teachos::arch::memory struct page_table { /** + * @brief Constructor. + */ + page_table(); + + /** * @brief Set every entry of the page to unused */ auto zero_entries() -> void; /** - * @brief Find and return the next table address + * @brief Convert the address of a page_table into a page_table * - * The next table address is only valid if the corresponding entry is present - * and does not create a huge page + * @param index Index of the entry we want to access + * @return An optional of the next page table or null + */ + auto next_table(std::size_t index) const -> std::optional<const page_table *>; + + /** + * @brief Index operator overload to access specific mutable entry directy * - * @param index - * @return An optional of the address of the next page table or null + * @param index Index of the entry we want to access and change + * @return Entry at the given table index */ - auto next_table_address(std::size_t index) const -> std::optional<std::size_t>; + auto operator[](std::size_t index) -> entry &; /** - * @brief Convert the address of a page_table into a page_table + * @brief Index operator overload to access specific immutable entry directy * - * @param index - * @return An optional of the next page table or null + * @param index Index of the entry we want to access and only read + * @return Entry at the given table index */ - auto next_table(std::size_t index) const -> std::optional<const page_table *>; + auto operator[](std::size_t index) const -> entry const &; + private: /** - * @brief Index operator overload to access specific entries directy + * @brief Find and return the next table address + * + * The next table address is only valid if the corresponding entry is present + * and does not create a huge page * * @param index - * @return The address of the accessed entry + * @return An optional of the address of the next page table or null */ - entry & operator[](std::size_t index); + auto next_table_address(std::size_t index) const -> std::optional<std::size_t>; - private: entry entries[PAGE_TABLE_ENTRY_COUNT]; - page_table const * p4 = reinterpret_cast<page_table *>(0xfffffffffffff000); + page_table const * p4; }; } // namespace teachos::arch::memory diff --git a/arch/x86_64/src/memory/paging.cpp b/arch/x86_64/src/memory/paging.cpp index a07b2c0..a8f2c40 100644 --- a/arch/x86_64/src/memory/paging.cpp +++ b/arch/x86_64/src/memory/paging.cpp @@ -40,25 +40,21 @@ namespace teachos::arch::memory flags = std::bitset<64U>(frame.start_address()) | flags; } - auto page_table::zero_entries() -> void + page_table::page_table() + : entries() + , p4(reinterpret_cast<page_table *>(0xfffffffffffff000)) { - for (size_t i = 0; i < sizeof(entries) / sizeof(entries[0]); ++i) - { - entries[i].set_unused(); - } + // Nothing to do } - auto page_table::next_table_address(std::size_t index) const -> std::optional<std::size_t> + auto page_table::zero_entries() -> void { - auto entry = entries[index]; - - if (entry.contains_flags(entry.PRESENT) && !entry.contains_flags(entry.HUGE_PAGE)) + constexpr size_t entry_amount = sizeof(entries) / sizeof(entries[0]); + for (size_t i = 0; i < entry_amount; ++i) { - std::size_t table_address = reinterpret_cast<std::size_t>(this); - return (table_address << 9) | (index << 12); + auto entry = this->operator[](i); + entry.set_unused(); } - // TODO: Implement behaviour for huge pages currently not done - return std::nullopt; } auto page_table::next_table(std::size_t index) const -> std::optional<page_table const *> @@ -73,9 +69,32 @@ namespace teachos::arch::memory return std::nullopt; } - entry & page_table::operator[](std::size_t index) + auto page_table::operator[](std::size_t index) -> entry & + { + // C array is not bounds checked, therefore we have to check ourselves, to ensure no out of bounds reads, which + // could be incredibly hard to debug later. + arch::exception_handling::assert(index < PAGE_TABLE_ENTRY_COUNT, "[Page Table] index out of bounds"); + return entries[index]; + } + + auto page_table::operator[](std::size_t index) const -> entry const & { + // C array is not bounds checked, therefore we have to check ourselves, to ensure no out of bounds reads, which + // could be incredibly hard to debug later. arch::exception_handling::assert(index < PAGE_TABLE_ENTRY_COUNT, "[Page Table] index out of bounds"); return entries[index]; } + + auto page_table::next_table_address(std::size_t index) const -> std::optional<std::size_t> + { + auto entry = this->operator[](index); + + if (entry.contains_flags(entry::PRESENT) && !entry.contains_flags(entry::HUGE_PAGE)) + { + std::size_t const table_address = reinterpret_cast<std::size_t>(this); + return (table_address << 9) | (index << 12); + } + // TODO: Implement behaviour for huge pages currently not done + return std::nullopt; + } } // namespace teachos::arch::memory |