GDT

include/boot/gdt.h

struct gdt_entry

Member Type	Member Name
uint16_t	limit_low
uint16_t	base_low
uint8_t	base_middle
uint8_t	access
uint8_t	granularity
uint8_t	base_high

struct gdt_ptr

Member Type	Member Name
uint16_t	limit
uint64_t	base

struct gdt_entry_tss

Member Type	Member Name
uint16_t	limit_low
uint16_t	base_low
uint8_t	base_middle
uint8_t	access
uint8_t	granularity
uint8_t	base_high
uint32_t	base_upper
uint32_t	reserved

• void gdt_install()

Defines

• ACCESS_CODE_RING0: 0x9A // exec/read, ring 0
• ACCESS_DATA_RING0: 0x92 // read/write, ring 0
• ACCESS_CODE_RING3: 0xFA // exec/read, ring 3
• ACCESS_DATA_RING3: 0xF2 // read/write, ring 3
• GRAN_CODE: 0xAF // G=1, D/B=0, L=1, AVL=0
• GRAN_DATA: 0xAF // G=1, D/B=0, L=0, AVL=0
• GDT_KERNEL_CODE: 0x08 // index 1
• GDT_KERNEL_DATA: 0x10 // index 2
• KERNEL_CS: GDT_KERNEL_CODE
• KERNEL_DS: GDT_KERNEL_DATA
• GDT_USER_CODE: 0x28 // index 5 << 3
• GDT_USER_DATA: 0x30 // index 6 << 3
• USER_CS: (GDT_USER_CODE | 0x3) // == 0x2B
• USER_DS: (GDT_USER_DATA | 0x3) // == 0x33
• USER_SS: USER_DS

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