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Switch from Real Mode to Protected Mode and Display Text

hard1/8

PrevBuild a Flat GDT for Protected Mode

Language

Compiler

2.0s Limit 256MB

Implementation

Implement real mode to protected mode transition.

Requirements:

Create Global Descriptor Table (GDT)
Load GDTR using LGDT instruction
Set CR0.PE bit to enable protected mode
Perform far jump to flush instruction queue
Load segment registers with protected mode selectors
Display text using video memory (no BIOS interrupts)
Demonstrate understanding of protected mode concepts
Use inline assembly or pure assembly
Include detailed comments explaining each step

Why This Matters

This CR0.PE-bit-plus-far-jump sequence is literally the first thing GRUB's `real2prot32` code and the Linux kernel's own boot/pm.c perform before the 32-bit kernel proper ever runs. Forgetting the far jump right after setting PE is a classic real bug: the CPU's prefetch queue still contains real-mode-decoded instructions, so skipping it crashes with garbage opcode execution instead of a clean switch.

Hints

0 / 3 revealed

Validation Suite

main.c

Workspace 1.0