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Updated GDT code

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This commit is contained in:
Alex
2022-11-05 07:36:57 +02:00
parent 8e579133cc
commit 14ccd20d9b
2 changed files with 100 additions and 51 deletions
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95
Architecture/amd64/cpu/gdt.hpp
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@ -5,39 +5,72 @@
namespace GlobalDescriptorTable
{
/* https://github.com/nanobyte-dev/nanobyte_os/blob/master/src/kernel/arch/i686/gdt.c */
/* https://wiki.osdev.org/Global_Descriptor_Table */
typedef enum
/** @brief The GDT Access Table
* @details For more information, see https://wiki.osdev.org/Global_Descriptor_Table
*/
union GlobalDescriptorTableAccess
{
CODE_READABLE = 0b00000010,
DATA_WRITEABLE = 0b00000010,
struct
{
/** @brief Access bit.
* @note The CPU sets this bit to 1 when the segment is accessed.
*/
uint8_t A : 1;
CODE_CONFORMING = 0b00000100,
DATA_DIRECTION_NORMAL = 0b00000000,
DATA_DIRECTION_DOWN = 0b00000100,
/** @brief Readable bit for code segments, writable bit for data segments.
* @details For code segments, this bit must be 1 for the segment to be readable.
* @details For data segments, this bit must be 1 for the segment to be writable.
*/
uint8_t RW : 1;
DATA_SEGMENT = 0b00010000,
CODE_SEGMENT = 0b00011000,
/** @brief Direction bit for data segments, conforming bit for code segments.
* @details For data segments, this bit must be 1 for the segment to grow up (higher addresses).
* @details For code segments, this bit must be 1 for code in the segment to be able to be executed from an equal or lower privilege level.
*/
uint8_t DC : 1;
DESCRIPTOR_TSS = 0b00000000,
/** @brief Executable bit.
* @details This bit must be 1 for code-segment descriptors.
* @details This bit must be 0 for data-segment and system descriptors.
*/
uint8_t E : 1;
RING0 = 0b00000000,
RING1 = 0b00100000,
RING2 = 0b01000000,
RING3 = 0b01100000,
/** @brief Descriptor type.
* @details This bit must be 0 for system descriptors.
* @details This bit must be 1 for code or data segment descriptor.
*/
uint8_t S : 1;
PRESENT = 0b10000000
} AccessFlags;
/** @brief Descriptor privilege level.
* @details This field determines the privilege level of the segment.
* @details 0 = kernel mode, 3 = user mode.
*/
uint8_t DPL : 2;
typedef enum
/** @brief Present bit.
* @details This bit must be 1 for all valid descriptors.
*/
uint8_t P : 1;
} __attribute__((packed));
uint8_t Raw;
};
union GlobalDescriptorTableFlags
{
_64BITS = 0b00100000,
_32BITS = 0b01000000,
_16BITS = 0b00000000,
// TODO: Add more flags.
struct
{
/** @brief Unknown. */
uint8_t Unknown : 5;
GRANULARITY_1B = 0b00000000,
GRANULARITY_4K = 0b10000000
} GDTFlags;
/** @brief Long mode.
* @details If the long mode bit is clear, the segment is in 32-bit protected mode.
* @details If the long mode bit is set, the segment is in 64-bit long mode.
*/
uint8_t L : 1;
} __attribute__((packed));
uint8_t Raw;
};
typedef struct _TaskStateSegmentEntry
{
@ -63,17 +96,17 @@ namespace GlobalDescriptorTable
typedef struct _GlobalDescriptorTableEntry
{
/** @brief Length [Bits 0-15] */
/** @brief Length */
uint16_t Length;
/** @brief Low Base [Bits 0-15] */
/** @brief Low Base */
uint16_t BaseLow;
/** @brief Middle Base [Bits 0-23] */
/** @brief Middle Base */
uint8_t BaseMiddle;
/** @brief Access */
uint8_t Access;
/** @brief Flags [Bits 16-19] */
uint8_t Flags;
/** @brief High Base [Bits 24-31] */
GlobalDescriptorTableAccess Access;
/** @brief Flags */
GlobalDescriptorTableFlags Flags;
/** @brief High Base */
uint8_t BaseHigh;
} __attribute__((packed)) GlobalDescriptorTableEntry;