UEFI Support for Memtest86+ Patricio Chilano Mateo

Transcription

1 UEFI Support for Memtest86+ Patricio Chilano Mateo 1

2 MEMTEST86+ Memory diagnostic tool for x86 and x86-64 platforms Release History - Initial release on 2004 as a fork of Memtest86 v3.0 - Latest release on 2013 as v Released under GPL Written in C and x86 Features - Support for most modern CPUs and chipsets - 2TB of RAM on x SMT support for up to 32 cores (experimental) - Coreboot support 2

3 UEFI Interface between firmware and operating system Provides Boot and Runtime services Advantages - Avoid CPU real mode - Slow - Only 1MB address space - Larger disks (2T) by means of GPT - Bootmanager - Flexible bootloader setup - Better interface - Mouse support - Graphics - UEFI Applications (shell) Source: 3

4 Goal Memtest86+ limitations (vs MemTest86) - Runs in BIOS environment - int 0x15 for getting memory size - VGA framebuffers for screen - int 0x10 for loading disk sectors (bootloader code, so probably not needed) Most modern motherboards have UEFI firmware Add support to run in UEFI - Compile as UEFI application (Maybe CDROM image) - 32 bit initially - Run in a UEFI platform (Galileo or Minnowboard) 4

5 Booting in UEFI EFI System Partition (ESP) - Extra partition in GPT disk - Contains EFI drivers, applications, boot loaders - FAT32 file system (could be fat16) - Convention to store bootloaders - /EFI/Ubuntu, /EFI/redhat, /EFI/boot NVRAM with list of boot options - How to save items in NVRAM? - If booted in UEFI mode use efibootmgr (linux) Bootmanager - Reads NVRAM list, tries each item until one doesn t return MACS do it a bit different - EFI firmware read HFS+ and loads bootlader 5 Source:

6 GNU-EFI - Simpler to use - Requires wrapping of function calls Development Tools TianoCore EFI Development Kit (EDKII) - Support for advanced or new EFI features qemu OVMF (Open Virtual Machine Firmware) - Tianocore image to run on Qemu gdb - attach gdb to qemu to debug applications 6

7 Code Base (Memtest86+) C ~ lines (*) in controller.c - interacts with the memory controller - reads and writes using pci (pci.c ~ 200 loc) in main.c and init.c - initializes the screen and calls the tests (not sure if should change) in custom libc in test.c in error.c in smp.c (multicore support) in memsize.c - gets memory information from linuxbios.c in screen_buffer.c - uses the VGA buffer to write to screen X86 Assembly ~ in head.s - Configures final gdt and idt, reloctes code and calls test_start() in main.c bootsect.s and setup.s should not be used (*) Lots of inline assembly in C code 7

8 Lines of Code to Write Getting memory information (~400) Printing to screen (~900) Managing relocations (~300) Exisiting memory controller shouldn t change Bootloader code should not be used if UEFI Application - Check in case of CDROM image main (not sure) Total > 1600 lines 8

9 Schedule (Optimistic) 10 weeks remaining Stage I (1 2 weeks) - Understand existing code - Develop sample UEFI applications Stage II (~2 weeks) - Compile memtest86+ as UEFI application - Retrieve memory information Stage III (~2-3 weeks) - Replace VGA framebuffers and print to screen Stage IV (~2 weeks) - Debugging / making it work - Fix relocations problems if necessary - Stage V (~1 week) - Try in real hardware 9

10 Challenges Understanding memtest86+ code base Reading UEFI spec (some!) UEFI development environment - Build complex applications with mix of x86 Assembly - C Calling UEFI services UEFI memory mappings (memtest86+ relocates itself) Debug uefi applications in qemu using gdb 10

11 Documentation UEFI specification UEFI Programming Intel Software Developer Manual 11

12 Additional features (would be nice) Native 64 bit code Add mouse support Write reports/logs in external drive Secure Boot Bootable from USB/CD - Dual Boot (BIOS and UEFI support in single image) 12