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(Mostly) entering long mode

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This commit is contained in:
Thomas Oltmann 2025-07-05 20:29:53 +02:00
parent 11cdc51979
commit 0bfcd7afd2
1 changed files with 32 additions and 6 deletions
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38
lboot.S
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@ -37,8 +37,9 @@ _start: cli
call print
call paging
mov $msg_fin, %si
mov $msg_long, %si
call print
call long
jmp hang
@ -231,6 +232,35 @@ _prnext: mov $COM1+5, %dx
_prdone: ret
// long: Enter long mode
long:
// Enable PAE
mov %cr4, %eax
or $0b100000, %eax
mov %eax, %cr4
// Load page table
mov pml4_ptr, %eax
mov %eax, %cr3
// Enable long mode
.set IA32_EFER, 0xC0000080
mov $IA32_EFER, %ecx
rdmsr
or $0x100, %eax
wrmsr
// Enable protected mode + paging
mov %cr0, %eax
or $0x80000001, %eax
mov %eax, %cr0
ret
// hang: sleep indefinitely
hang: hlt
jmp hang
// gdt: Protected mode / Unreal mode 16-bit GDT
gdt: // entry 0: null descriptor
.word 0
@ -257,10 +287,6 @@ gdt: // entry 0: null descriptor
gdt_ptr: .word gdt_size-1
.long gdt
// hang: sleep indefinitely
hang: hlt
jmp hang
// Messages to print
msg_start: .asciz "Netboot via fernlader v1 ...\r\n"
msg_a20: .asciz " * Enabling A20\r\n"
@ -268,7 +294,7 @@ msg_unreal: .asciz " * Unreal Mode\r\n"
msg_getmap: .asciz " * Memory Map\r\n"
msg_mkheap: .asciz " * Making Space\r\n"
msg_paging: .asciz " * Paging\r\n"
msg_fin: .asciz "Finished.\r\n"
msg_long: .asciz " * Long Mode\r\n"
msg_aerr: .asciz "panic: Out of heap space.\r\n"
heap_start: .long 0