2021-04-19 19:06:28 +02:00
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.globl _start
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.globl MB_INFO
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.extern _bss_start
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.extern _bss_end
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.extern boucane
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.set STACK_LOCATION, 0x1FFFFF
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.section .multiboot
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.set MB_MAGIC, 0xE85250D6
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.set MB_ARCH, 0x00000000
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.set MB_HEADER_LENGTH, (mb_header_end-mb_header_start)
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.set MB_CHECKSUM, -(MB_MAGIC+MB_ARCH+MB_HEADER_LENGTH)
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mb_header_start:
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.align 8
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.int MB_MAGIC
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.int MB_ARCH
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.int MB_HEADER_LENGTH
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.int MB_CHECKSUM
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# ----------- Address tag
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.align 8
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.short 2
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.short 0 # Not optional
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.int 24 # Size
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.int mb_header_start # header_addr
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.int mb_header_start # load_addr
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.int 0x0 # load_end_addr
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.int 0x0 # bss_end_addr
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# ----------- Addr tag
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.align 8
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.short 0x3
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.short 0
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.int 12
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.int _start
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# ----------- End tag
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.align 8
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.int 0x0
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.int 0x8
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mb_header_end:
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.section .text
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.code32 # Require since grub do not enable long mode
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MB_INFO:
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.int 0xABCDEF # Will contains the Multiboot2 information data structure address
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_start:
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mov %ebx,(MB_INFO)
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2021-04-21 12:23:54 +02:00
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# Zeroing the .bss section
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mov $_bss_start, %eax
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mov $_bss_end, %ebx
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start_zeroing:
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movb $0x0, (%eax)
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cmp %eax, %ebx
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je end_zeroing
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inc %eax
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jmp start_zeroing
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end_zeroing:
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2021-04-19 19:06:28 +02:00
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# ----- Setup PAE Paging (identity on the first 10MB)
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mov $8192, %ecx # 8*4096/4 (8 tables of 4096 byte each divide by 4 because of movl)
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mov $0, %eax
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zeroing_paging:
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movl $0, (%eax)
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add $4, %eax
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loop zeroing_paging
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# Setup PML4 Table (Address 0x0)
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mov $0x0, %edi
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mov %edi, %cr3 # Setup PML4 location
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movl $0x1003, (%edi) # Setup PDPT location
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# Setup PDPT
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mov $0x1000, %edi
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movl $0x2003, (%edi) # Setup PDPT location
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# Setup PDT (5 PT = 10MB)
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mov $0x2000, %edi
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mov $0x3003, %eax
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mov $5, %ecx
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pdt_fill:
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movl %eax, (%edi) # Setup PDPT location
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add $8, %edi # Goto next entry
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add $0x1000, %eax # Next PT
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loop pdt_fill
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# Setup the 5 PT
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mov $0x3000, %edi
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mov $0x3, %ebx # First map to 0
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mov $2560, %ecx # 512*5
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pt_fill:
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mov %ebx, (%edi)
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add $8, %edi # Next entry
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add $0x1000, %ebx # Next Page
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loop pt_fill
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# ----- Switch to compatibility mode
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# Set CR4.PAE
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mov %cr4, %eax
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bts $5, %eax
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mov %eax, %cr4
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# Set EFER.LME
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mov $0xC0000080, %ecx
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rdmsr
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bts $8, %eax
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wrmsr
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# Set CR0.PG
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mov %cr0, %eax
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bts $31, %eax
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mov %eax, %cr0
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# Now we are in Compatibility mode
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# Now we need to set CS.L=1 (setting up a 64 bit GDT)
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lgdt (gdtr)
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jmp $0x08, $new_cs
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new_cs:
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2021-04-21 18:54:50 +02:00
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# Pay attention here!
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# You are in long mode here
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# Thus if you want to add any instructions
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# You should use .code64 before
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.code64
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2021-04-21 12:23:54 +02:00
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mov $0x10, %ax
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mov %ax, %ds
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mov %ax, %es
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mov %ax, %fs
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mov %ax, %gs
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mov %ax, %ss
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2021-04-21 18:54:50 +02:00
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mov $STACK_LOCATION, %esp
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2021-04-21 12:23:54 +02:00
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2021-04-19 19:06:28 +02:00
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# Run boucane
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jmp boucane
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# GDT
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gdt64:
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gdt64_null:
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.long 0
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.long 0
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gdt64_cs:
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.long 0
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.byte 0
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.byte 0b10011100
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.byte 0b00100000
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.byte 0
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gdt64_ds:
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.long 0
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.byte 0
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2021-04-21 12:23:54 +02:00
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.byte 0b10010010
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2021-04-19 19:06:28 +02:00
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.word 0
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gdtr:
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.word . - gdt64 - 1
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2021-04-21 12:23:54 +02:00
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.quad gdt64
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