transfer to local git!

boot/boot.asm

@@ -0,0 +1,96 @@
+global start
+extern rust_handshake
+
+section .text
+bits 32
+start:
+    ; Grab stack pointer from GRUB
+    mov esp, stack_top
+
+    ; Setup paging for long mode
+    call set_up_page_tables
+    call enable_paging
+
+    ; load the 64-bit GDT
+    lgdt [gdt64.pointer]
+
+    jmp gdt64.code:rust_handshake
+
+    ; move 'ok' characters to VGA buffer
+    mov dword [0xb8000], 0x2f4b2f4f
+    hlt
+
+set_up_page_tables:
+    ; map first page-map table to page pointer table
+    mov eax, page_pointer_table
+    or eax, 0b11
+    mov [page_map_table], eax
+
+    ; map first page pointer table entry to page table table
+    mov eax, page_table
+    or eax, 0b11
+    mov [page_pointer_table], eax
+
+    ; map each page table entry to a 2M page
+    mov ecx, 0
+
+.map_page_table:
+    ; map ecx-th page_table entry to a page that starts at address 2MiB*ecx
+    mov eax, 0x200000  ; 2MiB
+    mul ecx            ; start address of ecx-th page
+    or eax, 0b10000011 ; present + writable + huge
+    mov [page_table + ecx * 8], eax ; map entry
+
+    ; This is a for loop to map all 512 entries
+    ; inside the page table
+    inc ecx ; i++
+    cmp ecx, 512 ; i != 512
+    jne .map_page_table  ; loop!
+
+    ret
+
+enable_paging:
+    ; load page map table to cr3 reg
+    mov eax, page_map_table
+    mov cr3, eax
+
+    ; enable physical address extension flag to cr4 reg
+    mov eax, cr4
+    or eax, 1 << 5
+    mov cr4, eax
+
+    ; set the long mode bit in the MSR
+    mov ecx, 0xC0000080
+    rdmsr
+    or eax, 1 << 8
+    wrmsr
+
+    ; enable paging in the cr0 reg
+    mov eax, cr0
+    or eax, 1 << 31
+    mov cr0, eax
+
+    ret
+
+; Align each table
+section .bss
+align 4096
+page_map_table:
+    resb 4096
+page_pointer_table:
+    resb 4096
+page_table:
+    resb 4096
+stack_bottom:
+    resb 64
+stack_top:
+
+; Global Descriptor Table Setup
+section .rodata
+gdt64:
+    dq 0
+.code: equ $ - gdt64
+    dq (1<<43) | (1<<44) | (1<<47) | (1<<53) ; code segment
+.pointer:
+    dw $ - gdt64 - 1
+    dq gdt64