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notcarbide edited this page Apr 4, 2022 · 9 revisions

Zap Kernel Wiki

This wiki contains useful information regarding the ZapPi Linux kernel.

Contents:

  1. Features
  2. Install
  3. Download
  4. Building

Features

  • Linux 5.15.y
  • Based on Raspberry Pi release tags for stability
  • 300Hz timer frequency for ARMv7+
  • Link Time Optimization
  • Compiled using ZLLVM
  • Compiler optimizations (-O3, -mtune to cpu, -polly, -compiler-rt)
  • Disabled debugging options to help performance
  • Multigenerational LRU (Disabled/Untested on ARMv6)
  • Rockchip Linux boot time optimizations
  • BBRv2 TCP congestion control
  • Mainline scheduler backports
  • Scheduler optimization by skipping some calculations
  • Misc enhancements from Android, Tizen, Linux
  • Tons of inspiration (+patches) from Zen Kernel

Install

Zap Kernel is intended to be a "drag-and-drop" replacement for Raspberry Pi OS.

Backup your kernel:

  • RPi0/1:
sudo cp /boot/kernel.img /boot/kernel-bck.img
  • RPi2/3 (+ Zero 2 W):
sudo cp /boot/kernel7.img /boot/kernel7-bck.img
  • RPi4:
sudo cp /boot/kernel7l.img /boot/kernel7l-bck.img
  • RPi64:
sudo cp /boot/kernel8.img /boot/kernel8-bck.img

Unzip the package into a directory:

unzip zap-kernel_*-202X-XX-XX.zip -d out

Run the install script within the extracted directory:

cd out
./install.sh

The backup kernel can be booted by adding, for example, the following to /boot/config.txt:

kernel=kernel7l-bck.img

Use whichever *-bck.img name referenced above.

Download

Downloads can be found in Releases

Signatures (.asc) included can be used to verify the downloaded file against uZap Maintainer's public key:

gpg --recv-keys D85C9504501468CB
gpg --verify zap-kernel*.zip.asc zap-kernel*.zip

Building

Compiling this kernel source requires the following dependencies:

sudo apt install git bc bison curl flex libssl-dev make libc6-dev libncurses5-dev libffi7

LLVM from most sources should be fine to cross compile with the 'compile' script to build, so long as LLVM_DIR is set to the root of the LLVM install.

Although ZLLVM is recommended for x86, as it is optimized to build this code, and can be easily downloaded with:

sh zap/get-zllvm.sh

Compiling the kernel can be done using something similar to the resulting output of the script, for example:

./compile rpi0w rpi2 rpi400 rpi64 LLVM_DIR=~/zllvm-14

will compile a 32-bit kernel for rpi0w, rpi2, rpi400 & the unified 64-bit kernel (for 64-bit capable devices).

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