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.section .text
.global _start
.align 8
multiboot2_header_start:
.long 0xE85250D6
.long 0
.long multiboot2_header_end - multiboot2_header_start
.long -(0xE85250D6 + 0 + (multiboot2_header_end - multiboot2_header_start))
.align 8
.short 0
.short 0
.long 8
multiboot2_header_end:
.code32
_start:
cli
mov %ebx, multiboot2_info_ptr
mov $boot_stack_top, %esp
call setup_page_tables
call enable_long_mode
lgdt gdt64_pointer
jmp $0x08, $long_mode_start
setup_page_tables:
# PML4[0] -> L3 (identity map first 512GB)
mov $page_table_l3, %eax
or $0b111, %eax
mov %eax, (page_table_l4)
# PML4[256] -> L3_high (higher-half at 0xFFFF800000000000)
mov $page_table_l3_high, %eax
or $0b111, %eax
mov %eax, (page_table_l4 + 2048)
# Setup L3 entries for identity mapping (first 4GB)
mov $page_table_l2_0, %eax
or $0b111, %eax
mov %eax, (page_table_l3)
mov $page_table_l2_1, %eax
or $0b111, %eax
mov %eax, (page_table_l3 + 8)
mov $page_table_l2_2, %eax
or $0b111, %eax
mov %eax, (page_table_l3 + 16)
mov $page_table_l2_3, %eax
or $0b111, %eax
mov %eax, (page_table_l3 + 24)
# Setup L3_high entries (map first 4GB to higher-half too)
mov $page_table_l2_high_0, %eax
or $0b111, %eax
mov %eax, (page_table_l3_high)
mov $page_table_l2_high_1, %eax
or $0b111, %eax
mov %eax, (page_table_l3_high + 8)
mov $page_table_l2_high_2, %eax
or $0b111, %eax
mov %eax, (page_table_l3_high + 16)
mov $page_table_l2_high_3, %eax
or $0b111, %eax
mov %eax, (page_table_l3_high + 24)
# Map 4GB identity (low)
mov $page_table_l2_0, %edi
mov $0x00000000, %edx
mov $0b10000111, %esi
call map_l2_table
mov $page_table_l2_1, %edi
mov $0x40000000, %edx
mov $0b10000111, %esi
call map_l2_table
mov $page_table_l2_2, %edi
mov $0x80000000, %edx
mov $0b10000111, %esi
call map_l2_table
mov $page_table_l2_3, %edi
mov $0xC0000000, %edx
mov $0b10000111, %esi
call map_l2_table
# Map 4GB to higher-half (same physical memory, different virtual addresses)
mov $page_table_l2_high_0, %edi
mov $0x00000000, %edx
mov $0b10000111, %esi
call map_l2_table
mov $page_table_l2_high_1, %edi
mov $0x40000000, %edx
mov $0b10000111, %esi
call map_l2_table
mov $page_table_l2_high_2, %edi
mov $0x80000000, %edx
mov $0b10000111, %esi
call map_l2_table
mov $page_table_l2_high_3, %edi
mov $0xC0000000, %edx
mov $0b10000111, %esi
call map_l2_table
ret
map_l2_table:
push %ebx
push %ecx
push %edx
mov %edx, %ebx
mov $0, %ecx
.map_loop:
mov %ebx, %eax
or %esi, %eax
mov %eax, (%edi,%ecx,8)
movl $0, 4(%edi,%ecx,8)
add $0x200000, %ebx
inc %ecx
cmp $512, %ecx
jne .map_loop
pop %edx
pop %ecx
pop %ebx
ret
enable_long_mode:
mov $page_table_l4, %eax
mov %eax, %cr3
mov %cr4, %eax
or $(1 << 5), %eax
mov %eax, %cr4
mov $0xC0000080, %ecx
rdmsr
or $(1 << 8), %eax
wrmsr
mov %cr0, %eax
or $(1 << 31), %eax
mov %eax, %cr0
ret
.code64
long_mode_start:
mov $0x10, %ax
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
mov %ax, %ss
mov $stack_top, %rsp
xor %rdi, %rdi
mov multiboot2_info_ptr(%rip), %edi
call mirai
halt:
hlt
jmp halt
.section .data
.align 4096
page_table_l4:
.skip 4096
page_table_l3:
.skip 4096
page_table_l2_0:
.skip 4096
page_table_l2_1:
.skip 4096
page_table_l2_2:
.skip 4096
page_table_l2_3:
.skip 4096
page_table_l3_high:
.skip 4096
page_table_l2_high_0:
.skip 4096
page_table_l2_high_1:
.skip 4096
page_table_l2_high_2:
.skip 4096
page_table_l2_high_3:
.skip 4096
.align 16
gdt64:
.quad 0
.quad 0x00AF9A000000FFFF
.quad 0x00AF92000000FFFF
gdt64_pointer:
.word gdt64_pointer - gdt64 - 1
.quad gdt64
multiboot2_info_ptr:
.long 0
.section .bss
.align 16
boot_stack_bottom:
.skip 4096
boot_stack_top:
stack_bottom:
.skip 16384
stack_top:
|
