diff options
6 files changed, 30 insertions, 33 deletions
diff --git a/arch/x86_64/include/arch/context_switching/descriptor_table/access_byte.hpp b/arch/x86_64/include/arch/context_switching/descriptor_table/access_byte.hpp index c510170..d1b579d 100644 --- a/arch/x86_64/include/arch/context_switching/descriptor_table/access_byte.hpp +++ b/arch/x86_64/include/arch/context_switching/descriptor_table/access_byte.hpp @@ -28,8 +28,8 @@ namespace teachos::arch::context_switching::descriptor_table ACCESS_LEVEL_PRIVILEGED_USER = 4, ///< Restricts access to own application and thoose of lower privilege. Should only be used if more than ///< two privilege levels are required, otherwise using Level 3 and Level 0 is recommended. - ACCESS_LEVEL_USER = 6, ///< Restricts access to only application and their specific memory. - DESCRIPTOR_TYPE = 1U << 3U, ///< Defines a system segment (if 0) or a code/data segment (if 1). + ACCESS_LEVEL_USER = 6, ///< Restricts access to only application and their specific memory. + CODE_OR_DATA_SEGMENT = 1U << 3U, ///< Defines a system segment (if 0) or a code/data segment (if 1). }; /** diff --git a/arch/x86_64/include/arch/context_switching/descriptor_table/gdt_flags.hpp b/arch/x86_64/include/arch/context_switching/descriptor_table/gdt_flags.hpp index ef8f2fa..bc6ecb7 100644 --- a/arch/x86_64/include/arch/context_switching/descriptor_table/gdt_flags.hpp +++ b/arch/x86_64/include/arch/context_switching/descriptor_table/gdt_flags.hpp @@ -38,13 +38,8 @@ namespace teachos::arch::context_switching::descriptor_table * @param flags Actual value read from the elf section header, which should be converted into a std::bitset, to * allow reading the state of single bits more easily. Only the rightmost 3 bit of the value will actually be * converted into the std::bitset, because the leftmost 4 bit are irrelevant and the 4th bit is reserved. - * - * @param type Depending on the segment descriptor type some of the passed bits are ignored. For system segment only - * the first bit Granularity is relevant, for the data segment the 3rd bit Length is irrelevant and for the code - * segment all bits are relevant. Bits that are not relevant will simply not be read and saved into the underlying - * flags std::bitset. */ - gdt_flags(uint8_t flags, segment_descriptor_type type); + gdt_flags(uint8_t flags); /** * @brief Checks if the given std::bitset is a subset or equivalent to the underlying std::bitset. diff --git a/arch/x86_64/include/arch/context_switching/descriptor_table/segment_descriptor.hpp b/arch/x86_64/include/arch/context_switching/descriptor_table/segment_descriptor.hpp index 59f99f6..364e546 100644 --- a/arch/x86_64/include/arch/context_switching/descriptor_table/segment_descriptor.hpp +++ b/arch/x86_64/include/arch/context_switching/descriptor_table/segment_descriptor.hpp @@ -32,6 +32,11 @@ namespace teachos::arch::context_switching::descriptor_table */ explicit segment_descriptor(uint128_t flags); + /** + * @brief Calculates the underlying segment type that this segement descriptor is describing. + */ + auto get_segment_type() const -> segment_descriptor_type; + private: uint32_t _reserved; access_byte _access; diff --git a/arch/x86_64/include/arch/context_switching/descriptor_table/type_field.hpp b/arch/x86_64/include/arch/context_switching/descriptor_table/type_field.hpp index 88e25cf..da61d38 100644 --- a/arch/x86_64/include/arch/context_switching/descriptor_table/type_field.hpp +++ b/arch/x86_64/include/arch/context_switching/descriptor_table/type_field.hpp @@ -18,10 +18,10 @@ namespace teachos::arch::context_switching::descriptor_table */ enum bitset : uint8_t { - TYPE = 1U << 0U, ///< Further defines the actual type of the segment. If enabled this segment is a code segment, - ///< otherwise its a data segment. - EXPAND_UP = 1U << 1U, ///< Indicates if the expansion direction is up or down in data segments. If enabled the - ///< data segment expands downwards, otherwise it expands upwards. + CODE_SEGMENT = 1U << 0U, ///< Further defines the actual type of the segment. If enabled this segment is a code + ///< segment, otherwise its a data segment. + EXPAND_UP = 1U << 1U, ///< Indicates if the expansion direction is up or down in data segments. If enabled the + ///< data segment expands downwards, otherwise it expands upwards. CONFORMING = 1U << 1U, ///< Indicates if the code is allowed to be executed by different access levels ///< (higher or lower) in code segments. If enabled the code segment allows access, otherwise diff --git a/arch/x86_64/src/context_switching/descriptor_table/gdt_flags.cpp b/arch/x86_64/src/context_switching/descriptor_table/gdt_flags.cpp index 8e1e939..8fbf869 100644 --- a/arch/x86_64/src/context_switching/descriptor_table/gdt_flags.cpp +++ b/arch/x86_64/src/context_switching/descriptor_table/gdt_flags.cpp @@ -4,24 +4,10 @@ namespace teachos::arch::context_switching::descriptor_table { - gdt_flags::gdt_flags(uint8_t flags, segment_descriptor_type type) + gdt_flags::gdt_flags(uint8_t flags) : _flags(flags << 5U) { - switch (type) - { - case segment_descriptor_type::SYSTEM_SEGMENT: - _flags.set(2, false); - _flags.set(3, false); - break; - case segment_descriptor_type::DATA_SEGMENT: - _flags.set(3, false); - break; - case segment_descriptor_type::CODE_SEGMENT: - exception_handling::assert((contains_flags(LENGTH) && !contains_flags(DEFAULT_LENGTH)) || - !contains_flags(LENGTH), - "[GDT] Flags of code segment descriptor has both "); - break; - } + // Nothing to do. } auto gdt_flags::contains_flags(std::bitset<4U> other) const -> bool { return (_flags & other) == other; } diff --git a/arch/x86_64/src/context_switching/descriptor_table/segment_descriptor.cpp b/arch/x86_64/src/context_switching/descriptor_table/segment_descriptor.cpp index fb9c034..57564f2 100644 --- a/arch/x86_64/src/context_switching/descriptor_table/segment_descriptor.cpp +++ b/arch/x86_64/src/context_switching/descriptor_table/segment_descriptor.cpp @@ -3,11 +3,22 @@ namespace teachos::arch::context_switching::descriptor_table { segment_descriptor::segment_descriptor(uint128_t flags) - : _reserved(flags) - , _access(flags) - , _flag(flags, segment_descriptor_type::SYSTEM_SEGMENT) - , _base(flags) - , _limit(flags) + : _reserved(flags >> 96U) + , _access((flags >> 40U) << 80U) + , _flag((flags >> 52U) << 72U) + , _base(((flags >> 64U) << 32U) << 32U | ((flags >> 56U) << 64U) << 24U | (flags >> 16U) << 88U) + , _limit(((flags >> 48U) << 72U) << 16U | flags << 112U) { + // Nothing to do. + } + + auto segment_descriptor::get_segment_type() const -> segment_descriptor_type + { + if (!_access.contains_flags(access_byte::CODE_OR_DATA_SEGMENT)) + { + return segment_descriptor_type::SYSTEM_SEGMENT; + } + return _access.get_type_field().contains_flags(type_field::CODE_SEGMENT) ? segment_descriptor_type::CODE_SEGMENT + : segment_descriptor_type::DATA_SEGMENT; } } // namespace teachos::arch::context_switching::descriptor_table |