145 lines
2.9 KiB
ArmAsm
145 lines
2.9 KiB
ArmAsm
/**
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* PROJECT: ExectOS
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* COPYRIGHT: See COPYING.md in the top level directory
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* FILE: boot/bootsect/amd64/cpu.S
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* DESCRIPTION: Low-level support for CPU initialization
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* DEVELOPERS: Aiken Harris <harraiken91@gmail.com>
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*/
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BuildPageMap:
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/* Generate page map for first 1GB of memory */
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pushaw
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pushw %es
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cld
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movw $(0x1000 / 16), %ax
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movw %ax, %es
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xorw %di, %di
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movl $(0x2000 | 0x07), %eax
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stosl
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xorl %eax, %eax
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movw $1021, %cx
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rep stosl
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movw $(0x2000 / 16), %ax
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movw %ax, %es
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xorw %di, %di
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movl $(0x3000 | 0x07), %eax
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stosl
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xorl %eax, %eax
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movw $1021, %cx
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rep stosl
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movw $(0x3000 / 16), %ax
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movw %ax, %es
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xorw %di, %di
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movw $512, %cx
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movl $0x00000083, %eax
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.BuildPageMapLoop:
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/* Identity map 512 pages of 2MB */
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movl %eax, %es:(%di)
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addl $2097152, %eax
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addw $0x08, %di
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loop .BuildPageMapLoop
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popw %es
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popaw
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ret
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InitializeCpu:
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/* Check if CPU supports CPUID, long mode and PAE */
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pushal
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pushfl
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popl %eax
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movl %eax, %ebx
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xorl $0x00200000, %eax
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pushl %eax
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popfl
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pushfl
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popl %eax
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cmpl %ebx, %eax
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je CpuUnsupported
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movl $0x01, %eax
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cpuid
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testl $0x40, %edx
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jz CpuUnsupported
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movl $0x80000000, %eax
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cpuid
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cmpl $0x80000000, %eax
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jbe CpuUnsupported
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movl $0x80000001, %eax
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cpuid
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testl $0x20000000, %edx
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jz CpuUnsupported
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popal
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call LoadGdt
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ret
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LoadGdt:
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/* Load Global Descriptor Table */
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lgdt .GdtPointer
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ret
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RunStage2:
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/* Switch to long mode and pass control to Stage 2 */
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call BuildPageMap
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call ParseExecutableHeader
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xorl %edx, %edx
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pushl %edx
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pushl %eax
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cli
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xorw %ax, %ax
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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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movw %ax, %ss
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movl %cr4, %eax
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orl $0x00A0, %eax
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movl %eax, %cr4
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movl $0x00001000, %eax
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movl %eax, %cr3
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movl $0xC0000080, %ecx
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rdmsr
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orl $0x00000100, %eax
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wrmsr
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movl %cr0, %eax
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orl $0x80000001, %eax
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movl %eax, %cr0
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ljmp $0x10, $.Stage2LongMode
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.code64
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.Stage2LongMode:
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/* Set segments and stack, then jump to Stage 2 */
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movw $0x18, %ax
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movw %ax, %ds
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movw %ax, %es
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movw %ax, %ss
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xorw %ax, %ax
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movw %ax, %fs
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movw %ax, %gs
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popq %rax
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xorq %rbx, %rbx
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xorq %rcx, %rcx
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xorq %rdx, %rdx
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xorq %rsi, %rsi
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xorq %rdi, %rdi
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xorq %rbp, %rbp
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jmp *%rax
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.code16
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.GdtDescriptor:
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/* Global Descriptor Table */
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.quad 0x0000000000000000
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.quad 0x0000000000000000
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.quad 0x00AF9A000000FFFF
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.quad 0x00CF92000000FFFF
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.quad 0x00009E000000FFFF
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.quad 0x000092000000FFFF
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.quad 0x00CF9B000000FFFF
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.GdtPointer:
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/* Pointer to Global Descriptor Table */
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.word .GdtPointer - .GdtDescriptor - 1
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.long .GdtDescriptor
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.Stage2FileName:
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/* Name of Stage 2 executable file */
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.ascii "BOOTX64 EFI"
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