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Rewritten GDT logic

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Nigel Barink
2021-11-16 21:17:49 +01:00
parent 3a87b74224
commit 88c5196586
5 changed files with 111 additions and 107 deletions
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74
src/kernel/gdt/gdt.s
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@ -1,75 +1,19 @@
/* Tell processor to use our gdt*/
gdt:
.word (gdt_end - gdt_start -1) # Size of the GDT in bytes minus 1 for math reasons
.int gdt_start # linear address of our GDT
.global LoadGlobalDescriptorTable
.att_syntax
LoadGlobalDescriptorTable:
lgdt gdtDescriptor
.global load_gdt
load_gdt:
lgdt gdt
# set the segment selecters
movw $0x10, %ax
movw $16, %ax
movw %ax, %ds
movw %ax, %es
movw %ax, %fs
movw %ax, %gs
movw %ax, %ss
ljmp $0x08, $flush
flush:
jmp $8,$flush
flush:
ret
#load idt
call init_idt
sti
# Try enable A20
# mov $0x2401, %ax
# int $0x15
# enable protected mode
mov %cr0, %eax
or $1, %eax
mov %eax, %cr0
call kernel_main
cli
1: hlt
jmp 1b
.size _start, . - _start
/*
* Create the GDT
*/
.section .data
gdt_start:
gdt_null:
.long 0x0
.long 0x0
gdt_kcode:
.word 0xFFFF # limit
.word 0x0 # base
.byte 0x0 # base
.byte 0b10011010 # 1st flags | type flags
.byte 0b11001111 # 2nd flags | limit
.byte 0x0 # base
gdt_kdata:
.word 0xFFFF # limit
.word 0x0 # base
.byte 0x0 # base
.byte 0b10010010 # 1st flags | type flags
.byte 0b11001111 # 2nd flags | limit
.byte 0x0 # base
gdt_end: