lessons 8, 9, 10, entering 32-bit mode

10-32bit-enter/32bit-main.asm

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+[org 0x7c00] ; bootloader offset
+    mov bp, 0x9000 ; set the stack
+    mov sp, bp
+
+    mov bx, MSG_REAL_MODE
+    call print ; This will be written after the BIOS messages
+
+    call switch_to_pm
+    jmp $ ; this will actually never be executed
+
+%include "../05-bootsector-functions-strings/boot_sect_print.asm"
+%include "../09-32bit-gdt/32bit-gdt.asm"
+%include "../08-32bit-print/32bit-print.asm"
+%include "32bit-switch.asm"
+
+[bits 32]
+BEGIN_PM: ; after the switch we will get here
+    mov ebx, MSG_PROT_MODE
+    call print_string_pm ; Note that this will be written at the top left corner
+    jmp $
+
+MSG_REAL_MODE db "Started in 16-bit real mode", 0
+MSG_PROT_MODE db "Loaded 32-bit protected mode", 0
+
+; bootsector
+times 510-($-$$) db 0
+dw 0xaa55

10-32bit-enter/32bit-switch.asm

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+[bits 16]
+switch_to_pm:
+    cli ; 1. disable interrupts
+    lgdt [gdt_descriptor] ; 2. load the GDT descriptor
+    mov eax, cr0
+    or eax, 0x1 ; 3. set 32-bit mode bit in cr0
+    mov cr0, eax
+    jmp CODE_SEG:init_pm ; 4. far jump by using a different segment
+
+[bits 32]
+init_pm: ; we are now using 32-bit instructions
+    mov ax, DATA_SEG ; 5. update the segment registers
+    mov ds, ax
+    mov ss, ax
+    mov es, ax
+    mov fs, ax
+    mov gs, ax
+
+    mov ebp, 0x90000 ; 6. update the stack right at the top of the free space
+    mov esp, ebp
+
+    call BEGIN_PM ; 7. Call a well-known label with useful code

10-32bit-enter/README.md

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+*Concepts you may want to Google beforehand: interrupts, pipelining*
+
+**Goal: Enter 32-bit protected mode and test our code from previous lessons**
+
+To jump into 32-bit mode:
+
+1. Disable interrupts
+2. Load our GDT
+3. Set a bit on the CPU control register `cr0`
+4. Flush the CPU pipeline by issuing a carefully crafted far jump
+5. Update all the segment registers
+6. Update the stack
+7. Call to a well-known label which contains the first useful code in 32 bits
+
+We will encapsulate this process on the file `32bit-switch.asm`. Open it
+and take a look at the code.
+
+After entering 32-bit mode, we will call `BEGIN_PM` which is the entry point
+for our actual useful code (e.g. kernel code, etc). You can read the code
+at `32bit-main.asm`. Compile and run this last file and you will see the two 
+messages on the screen.
+
+Congratulations! Our next step will be to write a simple kernel