161 lines
3.5 KiB
ArmAsm
161 lines
3.5 KiB
ArmAsm
/*
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* Multiboot Entry
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*/
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#define STACK_SIZE 0x4000
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#define MULTIBOOT_HEADER_MAGIC 0x1BADB002
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#define MULTIBOOT_HEADER_FLAGS 0x00010003
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//#define KERNEL_BASE 0x0000000000000000
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#define KERNEL_BASE 0xFFFF800000000000
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#define LOWMEM(_x) (_x - KERNEL_BASE)
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.extern mb_entry
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.text
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/**
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* _start --
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*
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* ELF entry point.
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*/
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.globl _start
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_start: .code32
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jmp multiboot_entry
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/**
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* This header needs to be present near the start of the ELF binary that
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* describes how the loader should load the operating system image into memory.
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*/
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.align 4
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multiboot_header: .code32
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.long MULTIBOOT_HEADER_MAGIC
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.long MULTIBOOT_HEADER_FLAGS
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.long -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)
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.long LOWMEM(multiboot_header)
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.long LOWMEM(_start)
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.long LOWMEM(_edata)
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.long LOWMEM(_end)
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.long LOWMEM(multiboot_entry)
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//
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// Multiboot entry
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// %eax: Magic (0x2BADB002)
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// %ebx: multiboot info structure
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//
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multiboot_entry: .code32
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// Save multiboot magic
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movl %eax, %edx
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// Setup the stack pointer
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movl $LOWMEM(lmfarptr), %edi
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movw $(0x7000 + 'A'), (0xB8000)
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movl $LOWMEM(stack + STACK_SIZE), %esp
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// Reset EFLAGS to a known state
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movw $(0x7000 + 'B'), (0xB8002)
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pushl $0
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popf
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// Configure the CPU control register cr4
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movw $(0x7000 + 'C'), (0xB8004)
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movl %cr4, %eax
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orl $0x0000006A0, %eax
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movl %eax, %cr4
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// Load the 32-bit page table
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movw $(0x7000 + 'D'), (0xB8006)
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movl $LOWMEM(bootpgtbl1), %eax
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movl %eax, %cr3
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// Enable 64-bit mode (long mode) and no-execute (NX) support
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movw $(0x7000 + 'E'), (0xB8008)
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movl $0xC0000080, %ecx
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rdmsr
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orl $0x0900, %eax
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wrmsr
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// Load the GDT that contains segment descriptors.
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movw $(0x7000 + 'E'), (0xB800A)
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movl $LOWMEM(bootgdtdesc), %eax
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lgdt (%eax)
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// Configure cr0
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movw $(0x7000 + 'F'), (0xB800C)
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movl %cr0, %eax
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orl $0x8005002B, %eax
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movl %eax, %cr0
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// Long jump into 64-bit mode
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movw $(0x7000 + '0'), (0xB800E)
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ljmp *(%edi)
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// No we're playing with power
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lmenter: .code64
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movw $(0x7000 + '1'), (0xB8010)
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xorw %ax, %ax
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movw %ax, %ss
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movw %ax, %ds
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movw %ax, %es
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movw %ax, %fs
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movw %ax, %gs
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movq $LOWMEM(stack + STACK_SIZE), %rax
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movq $0xFFFF8000, %rcx
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shlq $32, %rcx
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orq %rcx, %rax
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movq %rax, %rsp
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// Long jump into the high memory address where the kernel executes in
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movq $LOWMEM(lmhighptr), %rdi
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jmp *(%rdi)
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lmhigh:
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movw $(0x7000 + '2'), (0xB8012)
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movq %rdx, %rdi // Magic
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movq %rbx, %rsi // Multiboot info pointer
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call MachineBoot_Entry
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# Print halt to the graphics memory if we return
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movw $(0x5000 + 'H'), (0xB8098)
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movw $(0x5000 + 'A'), (0xB809A)
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movw $(0x5000 + 'L'), (0xB809C)
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movw $(0x5000 + 'T'), (0xB809E)
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loop:
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hlt
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jmp loop
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.p2align 4
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lmfarptr:
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.long LOWMEM(lmenter)
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.word 0x08
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.p2align 4
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lmhighptr:
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.quad lmhigh
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.p2align 12
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bootgdt:
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.quad 0x0000000000000000 /* Null */
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.quad 0x00AF9A000000FFFF /* Kernel CS */
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.quad 0x00CF92000000FFFF /* Kernel DS */
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.quad 0x0000000000000000
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.quad 0x0000000000000000
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.quad 0x0000000000000000
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.quad 0x0000000000000000
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.quad 0x0000000000000000
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.p2align 4
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.globl bootgdtdesc
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bootgdtdesc:
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.word 0x003F
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.quad LOWMEM(bootgdt)
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// Boot stack
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.p2align 12
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.globl stack
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.comm stack, STACK_SIZE
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