100 lines
1.4 KiB
ArmAsm
100 lines
1.4 KiB
ArmAsm
#include <memory.h>
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.intel_syntax noprefix
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.section .bss
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.align PAGE_SIZE
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.skip PAGE_SIZE
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BootStack:
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.section .text
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.code32
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.global _start
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_start:
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cli
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mov edi, eax
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mov esi, ebx
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//; Set up a known stack
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mov esp, offset V2P(BootStack)
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//; Set CR4.PAE
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//; enabling Page Address Extension
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mov eax, cr4
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or eax, 1<<5
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mov cr4, eax
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//; Load a P4 page table
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mov eax, offset V2P(BootP4)
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mov cr3, eax
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//; Set EFER.LME
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//; enabling Long Mode
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mov ecx, 0x0C0000080
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rdmsr
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or eax, 1<<8
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wrmsr
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//; Set CR0.PG
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//; enabling Paging
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mov eax, cr0
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or eax, 1<<31
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mov cr0, eax
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//; Load a new GDT
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lgdt [V2P(BootGDTp)]
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//; and update the code selector by a long jump
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jmp 0x8:V2P(long_mode_start)
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.code64
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long_mode_start:
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//; Clear out all other selectors
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mov eax, 0x0
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mov ss, eax
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mov ds, eax
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mov es, eax
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//; Jump to kernel address space
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movabs rax, offset upper_memory
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jmp rax
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upper_memory:
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//; Move stack pointer to kernel space
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mov rax, KERNEL_OFFSET
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add rsp, rax
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//; Remove identity mapping
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mov rax, 0
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movabs [BootP4], rax
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//; Update page tables
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mov rax, cr3
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mov cr3, rax
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//; Reload GDT
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movabs rax, offset BootGDTp
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lgdt [rax]
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mov rax, 0x0
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mov ss, rax
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mov ds, rax
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mov es, rax
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//; Reload CS
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movabs rax, offset .reload_cs
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pushq 0x8
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push rax
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retfq
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.reload_cs:
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//; Jump to kmain()
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.extern kmain
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movabs rax, offset kmain
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call rax
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hlt
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jmp $
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