200 lines
3.5 KiB
ArmAsm
200 lines
3.5 KiB
ArmAsm
# Declare constants for the multiboot header
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.set ALIGN, 1<<0 # align loaded modules on page boundaries
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.set MEMINFO, 1<<1 # provide memory map
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.set VIDEOINFO, 1<<2 # provide video info
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.set MB_FLAGS, ALIGN | MEMINFO | VIDEOINFO # this is the Multiboot 'flag' field
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.set MB_MAGIC, 0x1BADB002 # 'magic number' lets bootloader find the header
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.set MB_CHECKSUM, -(MB_MAGIC + MB_FLAGS) #checksum of above, to prove we are multiboot
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.set PG_PRESENT, 1<<0
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.set PG_READ_WRITE, 1<<1
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.set PG_PAGE_SIZE, 1<<7
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.code32
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# Multiboot header
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.section .multiboot, "aw"
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.align 4
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.long MB_MAGIC
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.long MB_FLAGS
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.long MB_CHECKSUM
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.skip 20
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.long 0
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.long 800
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.long 600
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.long 32
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.section .bss, "aw", @nobits
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# Create stack
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stack_bottom:
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.skip 16384
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stack_top:
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.global g_kernel_cmdline
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g_kernel_cmdline:
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.skip 4096
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# Reserve memory for paging structures,
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# we will identity map first 4 MiB
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# 0 MiB -> 1 MiB: bootloader stuff
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# 1 MiB -> 2 MiB: kernel
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# 2 MiB -> 3 MiB: kmalloc
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# 3 MiB -> 4 MiB: kmalloc_eternal
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.align 4096
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boot_pml4:
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.skip 512 * 8
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boot_pdpt1:
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.skip 512 * 8
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boot_pd1:
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.skip 512 * 8
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.section .text, "a"
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.global g_multiboot_info
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g_multiboot_info:
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.skip 8
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.global g_multiboot_magic
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g_multiboot_magic:
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.skip 8
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boot_gdt:
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.quad 0 // null
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.quad (1<<53) | (1<<47) | (1<<44) | (1<<43) // kernel code P,S,E,L (present, code/data, executable, long mode)
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boot_gdtr:
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.short . - boot_gdt - 1
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.quad boot_gdt
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has_cpuid:
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pushfl
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pushfl
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xorl $0x00200000, (%esp)
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popfl
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pushfl
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popl %eax
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xorl (%esp), %eax
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popfl
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testl $0x00200000, %eax
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ret
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is_64_bit:
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movl $0x80000000, %eax
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cpuid
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cmpl $0x80000001, %eax
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jl .no_extension
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movl $0x80000001, %eax
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cpuid
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testl $(1 << 29), %edx
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ret
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.no_extension:
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cmpl %eax, %eax
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ret
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check_requirements:
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call has_cpuid
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jz .exit
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call is_64_bit
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jz .exit
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ret
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.exit:
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jmp system_halt
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copy_kernel_commandline:
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pushl %esi
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pushl %edi
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movl g_multiboot_info, %esi
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addl $16, %esi
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movl (%esi), %esi
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movl $1024, %ecx
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movl $g_kernel_cmdline, %edi
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rep movsl
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popl %edi
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popl %esi
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ret
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enable_sse:
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movl %cr0, %eax
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andw $0xFFFB, %ax
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orw $0x0002, %ax
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movl %eax, %cr0
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movl %cr4, %eax
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orw $0x0600, %ax
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movl %eax, %cr4
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ret
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initialize_paging:
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# identity map first 4 MiB
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movl $(0x00000000 + PG_PAGE_SIZE + PG_READ_WRITE + PG_PRESENT), boot_pd1 + 0
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movl $(0x00200000 + PG_PAGE_SIZE + PG_READ_WRITE + PG_PRESENT), boot_pd1 + 8
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# set pdpte1 and pml4e1
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movl $(boot_pd1 + PG_READ_WRITE + PG_PRESENT), boot_pdpt1
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movl $(boot_pdpt1 + PG_READ_WRITE + PG_PRESENT), boot_pml4
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# enable PAE
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movl %cr4, %ecx
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orl $0x20, %ecx
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movl %ecx, %cr4
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# set long mode enable bit
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movl $0x100, %eax
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movl $0x000, %edx
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movl $0xC0000080, %ecx
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wrmsr
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# set address of paging structures
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movl $boot_pml4, %ecx
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movl %ecx, %cr3
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# enable paging
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movl %cr0, %ecx
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orl $0x80000000, %ecx
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movl %ecx, %cr0
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ret
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.global _start
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.type _start, @function
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_start:
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# Initialize stack and multiboot info
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movl $stack_top, %esp
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movl %eax, g_multiboot_magic
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movl %ebx, g_multiboot_info
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call copy_kernel_commandline
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call check_requirements
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call enable_sse
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call initialize_paging
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# flush gdt and jump to 64 bit
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lgdt boot_gdtr
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ljmpl $0x08, $long_mode
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.code64
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long_mode:
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# clear segment registers
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movw $0x00, %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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# call global constuctors
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call _init
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# call to the kernel itself (clear ebp for stacktrace)
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xorq %rbp, %rbp
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call kernel_main
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# call global destructors
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call _fini
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system_halt:
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xchgw %bx, %bx
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cli
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1: hlt
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jmp 1b
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