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modify gdt

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This commit is contained in:
Murphy 2025-04-07 12:37:39 -04:00
parent 78def513c7
commit a4464d3a71
Signed by: freya
GPG key ID: 9FBC6FFD6D2DBF17
1 changed files with 30 additions and 9 deletions

39
kernel/entry.S
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@ -47,7 +47,7 @@ kern_stack_start:
.skip 8192
kern_stack_end:
.section .rodata
.section .data
.align 16
# access bits
@ -58,6 +58,12 @@ kern_stack_end:
.set RW, 1 << 1
.set ACCESSED, 1 << 0
# privlage level (access bit)
.set RING0, 0 << 5
.set RING1, 1 << 5
.set RING2, 2 << 5
.set RING3, 3 << 5
# flag bits
.set GRAN_4K, 1 << 7
.set SZ_32, 1 << 6
@ -65,30 +71,45 @@ kern_stack_end:
# kernel gdt (long mode)
GDT:
# Null Segment
# Null Segment (0x00)
.equ GDT.Null, . - GDT
.quad 0
# Code segment
# Kernel Code segment (0x08)
.equ GDT.Code, . - GDT
.long 0xFFFF
.byte 0
.byte PRESENT | NOT_SYS | EXEC | RW
.byte PRESENT | NOT_SYS | EXEC | RW | RING0
.byte GRAN_4K | LONG_MODE | 0xF
.byte 0
# Data segment
# Kernel Data segment (0x10)
.equ GDT.Data, . - GDT
.long 0xFFFF
.byte 0
.byte PRESENT | NOT_SYS | RW
.byte PRESENT | NOT_SYS | RW | RING0
.byte GRAN_4K | SZ_32 | 0xF
.byte 0
# TSS segment
# User Code Segment (0x18)
.equ GDT.UserCode, . - GDT
.long 0xFFFF
.byte 0
.byte PRESENT | NOT_SYS | EXEC | RW | RING3
.byte GRAN_4K | LONG_MODE | 0xF
.byte 0
# User Data Segment (0x20)
.equ GDT.UserData, . - GDT
.long 0xFFFF
.byte 0
.byte PRESENT | NOT_SYS | RW | RING3
.byte GRAN_4K | SZ_32 | 0xF
.byte 0
# TSS segment (0x28)
.equ GDT.TSS, . - GDT
.long 0x00000068
.long 0x00CF8900
.quad 0 # to be modified in kernel
# GDT Pointer
.equ GDT.Pointer, .