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working entry for long mode

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This commit is contained in:
Murphy 2025-04-03 14:38:56 -04:00
parent a524eb3846
commit 77d1938420
Signed by: freya
GPG key ID: 9FBC6FFD6D2DBF17
1 changed files with 48 additions and 27 deletions

75
kernel/entry.S
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@ -8,6 +8,22 @@
.extern main
.extern GDT
.section .multiboot
.align 8
# multiboot header
mb_start:
# magic
.long 0xe85250d6
.long 0
.long mb_end - mb_start
.long 0x100000000 - (0xe85250d6 + (mb_end - mb_start))
# null
.short 0
.short 0
.long 8
mb_end:
.section .bss
# kernel page tables
@ -49,29 +65,35 @@ kern_stack_end:
# kernel gdt (long mode)
GDT:
GDT.Null:
.quad 0
# Null Segment
.equ GDT.Null, . - GDT
.quad 0
GDT.Code:
.byte 0
.byte PRESENT | NOT_SYS | EXEC | RW
.byte GRAN_4K | LONG_MODE | 0xF
.byte 0
# Code segment
.equ GDT.Code, . - GDT
.long 0xFFFF
.byte 0
.byte PRESENT | NOT_SYS | EXEC | RW
.byte GRAN_4K | LONG_MODE | 0xF
.byte 0
GDT.Data:
.long 0xFFFF
.byte 0
.byte PRESENT | NOT_SYS | RW
.byte GRAN_4K | SZ_32 | 0xF
.byte 0
# Data segment
.equ GDT.Data, . - GDT
.long 0xFFFF
.byte 0
.byte PRESENT | NOT_SYS | RW
.byte GRAN_4K | SZ_32 | 0xF
.byte 0
GDT.TSS:
.long 0x00000068
.long 0x00CF8900
# TSS segment
.equ GDT.TSS, . - GDT
.long 0x00000068
.long 0x00CF8900
GDT.Pointer:
.short . - GDT - 1
.quad GDT - .
# GDT Pointer
.equ GDT.Pointer, .
.word . - GDT - 1
.quad GDT
.section .text
.code32
@ -91,7 +113,7 @@ _start:
push %eax
# zero out kernel page table
movl $0x1000, %edi # kernel is loaded at 0x1000
movl $0x1000, %edi # pml4 located at 0x1000
movl %edi, %cr3
xorl %eax, %eax
movl $4096, %ecx # zero 4096 pages
@ -106,15 +128,15 @@ _start:
movl $kernel_pt_0 + 3, (%edi) # Set the uint32_t at the desination index to 0x4003.
movl $kernel_pt_0, %edi # Add 0x1000 to the desination index.
movl $0x00000003, %ebx # Entry value to set
movl $512, %ecx # Loop count
movl $0x03, %ebx # Entry value to set
movl $512, %ecx # Loop count
set_entry:
_start.SetEntry:
# set entires in mapping
movl %ebx, (%edi) # Set the uint32_t at the desination index to the B-register
addl $0x1000, %ebx # Add 0x1000 to the B-register
addl $8, %edi # Add eight to the desination index
loop set_entry
loop _start.SetEntry
# enable page address extension
movl %cr4, %eax
@ -122,7 +144,7 @@ set_entry:
movl %eax, %cr4
# enable long mode
movl $0xC0000080, %eax
movl $0xC0000080, %ecx
rdmsr
orl $(1 << 8), %eax
wrmsr
@ -134,7 +156,7 @@ set_entry:
# load gdt
lgdt GDT.Pointer
ljmp $16, $code64
ljmp $GDT.Code, $code64
.code64
code64:
@ -148,7 +170,6 @@ code64:
pop %rdi # pop possible multiboot header
pop %rsi
sti
call main
cli