Qemu x86 BIOS @ https://youtu.be/F71LGSrj9cc
- 2. Agenda ● QEMU or Quick EMUlator ● Bootloader overview ● X86 booting mechanism ● BIOS to boot sector code transfer demo ● U-Boot demo for x86 using QEMU
- 3. Disclaimer ● Presenter will not be responsible for for any damage to USB or HDD due to experiments followed. ● Take a note of all the instructions carefully ● Don’t use your hard disk for bootloader experiments. ● Presenter will use either QEMU or old x86 based system
- 4. QEMU ● QEMU is a generic open source machine emulator and virtualizer ● Emulates program written for one architecture in another ● It can run virtual machines like KVM in host CPU ● Installation – sudo apt install qemu-system – If error – sudo apt install qemu-system --fix-missing
- 5. Bootloader ● BIOS →UEFI ● 8xxROM→PPCboot—Armboot merged--→U-boot ● TianoCore – open source implementation of UEFI ● LinuxBIOS-->Coreboot ● Libreboot ● Both Coreboot and Libreboot are aimed to replace proprietary boot firmware
- 6. X86 booting mechanism ● Hardware Reset ● BIOS(Basic Input/Output System) or Platform Firmware in ASM – Resides in non-volatile memory and prepares all POST procedures – Interactive hardware configuration – Boot mode ● UEFI / CSM(Compatibility Support Mode)/BIOS ● Boot Loader – Extensible Firmware Interface (EFI) – Unified Extensible Firmware Interface(UEFI) written in C ● Boot Partition Format – Boot loader support also depends on type of partition ● MBR(Master Boot Record) disk partition ● GPT(GUID Partion Table) disk partition
- 7. Custom boot.asm● org 0x7C00 ;BIOS loads program here ● bits 16 ;16-bit mode ● start: ● cli ;Disable Interrupts ● mov si, welcm ;SI points to custom data ● mov ah, 0x0E ; Tell BIOS to print characters ● .loop lodsb ;load byte into AL – or al, al – jz halt – jmp .loop ● halt: hlt ● welcm: db “Embedkari Welcomes You! “ ● times 510 - ($ - $$) db 0 ;Fills remaining bytes except last two ● dw 0xAA55
- 8. Custom boot sector Experiment ● nasm(Netwide Assembler) Open source s/w for x86 – sudo apt update – Check and install build-essential if not present – sudo apt list | grep build | grep essential – sudo apt install nasm ● nasm boot.asm -f bin -o boot.bin ● You may verify assembly listing using – nasm boot.asm -l boot.lst ● Check the binary in QEMU ● qemu-system-i386 -fda boot.bin
- 10. Program boot.bin to USB ● USB data can be verified if required ● Start Cygwin as adminstrator ● dd if=/dev/sdb bs=512 count=4 of=test.bin
- 11. U-Boot-x86 @QEMU ● git clone git://git.denx.de/u-boot-x86.git ● cd u-boot-x86 ● export BUILD_ROM=y ● make qemu-x86_defconfig ● make all ● Test U-boot in QEMU ● qemu-system-i386 -nographic -bios u- boot.rom -net nic -net user,tftp=/tftpboot
- 12. U-Boot build issue ● You may get error due to absence of required Libraries and this may lead to following additional installation ● For missing swig – sudo apt install swig ● For Python 2 – sudo apt install python-dev ● For Python 3 – sudo apt install python3-dev
- 14. THANKS If you found this information usefule < Please like this video AND subscribe to www.youtube.com/c/embedkari Embedded Career Information : www.facebook.com/embedkari Blog:www.embedkari.com