Tag: GreenThreads-UEFI

UEFIThreads: EFIDroid’s port of LittleKernel’s thread library for UEFI

~ hucktech ~ Leave a comment

UEFI is event-based, not thread-based. Earlier this month, Michael Zimmermann of the EFIDroid project posted a message on the EDK2-devel list about EFIDroid’s thread library support for UEFI, which is based on the Little Kernel threads implementation, and comparing it to the GreenThreads-UEFI project. Edited (footnotified) version of Michael’s message below.

IMO this [GreenThreads-UEFI] library[0] has some crucial problems like changing the TPL during context switching. For my project “EFIDroid” I’ve invested many months analyzing, testing and implementing my own threading implementation based on LK(LittleKernel, a MIT licensed project) threads and get/set -context. The result is a pretty stable implementation which can even be used in UEFI drivers[1]. I’m currently using this lib for my LKL(LinuxKernelLibrary) port to be able to use linux touchscreen drivers in UEFI – so you could say it has been well tested. The only “problem” is that it only supports ARM right now and that the get/set context implementation was copied (and simplified) from glibc which means that this part is GPL code.

From the Little Kernel web site:

Who is using LK?
* LK is the Android bootloader and is also used in Android Trusted Execution Environment – “Trusty TEE” Operating System.
* Newer Android phones have some chance of LK running all the time alongside Linux.
* A few ARM SoC manufacturers use LK as their default bootloader such as DragonBoard 410c based on Qualcomm Snapdragon 410 processor.
* The Fuchsia Operating System’s microkernel, Zircon is based on LK.

[0] https://github.com/Openwide-Ingenierie/GreenThreads-UEFI
[1] https://github.com/efidroid/uefi_edk2packages_EFIDroidLKLPkg/tree/master/UEFIThreads
http://efidroid.org/

https://github.com/littlekernel
https://github.com/littlekernel/lk/wiki/Introduction
https://github.com/littlekernel/lk/blob/master/kernel/thread.c

Click to access lm80-p0436-1_little_kernel_boot_loader_overview.pdf

https://android.googlesource.com/kernel/lk/

Full message: 2017-11-02 post on EDK2-devel.

Green Threads for UEFI

~ hucktech ~ Leave a comment

Green Threads for UEFI: This project is a an alpha version of “green” threads for UEFI. It’s not really like Linux green threads as there is no distinction between user space and kernel space but the different threads are running on the same core

This C-based project has a bit of Intel-centric assembly language code.

Wikipedia defines “Green Threads” as: “threads that are scheduled by a runtime library or virtual machine (VM) instead of natively by the underlying operating system. Green threads emulate multithreaded environments without relying on any native OS capabilities, and they are managed in user space instead of kernel space, enabling them to work in environments that do not have native thread support.”

https://github.com/Openwide-Ingenierie/GreenThreads-UEFI

https://en.wikipedia.org/wiki/Green_threads