The best type of software bug is one where you get to learn something along the way. Like any good disaster, the bug we’re going to explore is one that arose from a chain of unexpected events and bad assumptions. This bug relates to uninitialised data and gives a good insight into the inner workings …
Author: Andrew Murray
Multiple UVC cameras on Linux: an unexpected challenge
Earlier this year one of our customers presented us with an unexpected problem: they weren’t able to stream video from multiple USB UVC web cameras – instead they got a “No space left on device” error. In our quest to provide a solution we learnt a little about USB and so we thought we’d share …
Xmas Charity Fundraiser 2020
This Xmas the Good Penguin is raising money for Sparkle, a charity in our local community that supports children, young people, and their families, with disabilities and/or developmental difficulties. Verity Cadwallader, a corporate fundraiser at Sparkle tells us, “We support over 300 families per week through delivering activities and clubs such as independent living skills, …
Build and Boot U-Boot and Linux on a Raspberry Pi 3 Model B+
With more than 30 million units in existence, the Raspberry Pi provides for an accessible and low-cost way to play with an ARMv8 embedded device using the latest and greatest upstream sources. In this post we’ll walk through the steps required to build U-Boot, the Linux kernel and a filesystem, as well as the steps …
i.MX6 UL Bus Encryption Engine (BEE) in the Linux Kernel
The ubiquitous i.MX6 Ultra Lite is high performance processor that offers a wide range of hardware security features such as ARM TrustZone, High Assurance Boot (HAB) and a Cryptographic Acceleration and Assurance Module (CAAM). The exact features and details depend on the specific part and are documented in detail in the Security Reference Manual (locked …
Discovering CPU features from userspace with ELF_HWCAP
As hardware architectures evolve they introduce new features – many of these features are abstracted away by the kernel yet result in some benefit to the user such as improved security or performance. However some features, like the introduction of a new CPU instruction can only benefit user-space if user-space is able to determine that …
Booting ARM without an ARM
It’s possible (and easy) to develop software for ARM based platforms without having physical ARM based hardware on your desk – there are many ways to do this such as using the QEMU emulator. However by using something known as a Fixed Virtual Platform (FVP) it’s possible to run software on a simulation of some …
The indirection of outb, iowrite and friends
The {in,out}{b,w,l} functions of the kernel provide the mechanism for reading from and writing to what we may describe as port I/O (PIO). The API is not architecture specific and thus present in most architectures and used by a wide variety of device drivers. However the mechanism to support PIO varies widely between architectures and …