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Author Archives: Niall Cooling
Disassembling a Cortex-M raw binary file with Ghidra
BlackHat Europe 2022
During the first week of December, I had the pleasure of attending a training course at BlackHat Europe 2022 titled Assessing and Exploiting Control Systems and IIoT run by Justin Searle.
Part of the course involved Assessing and Exploiting Embedded Firmware by reading on-chip Flash using OpenOCD. Unfortunately, we ran out of time to finish the last labs during the training (we ran 9 am-6 pm each day). So I decided to follow along with the very comprehensive notes […]
Using final in C++ to improve performance
Dynamic polymorphism (virtual functions) is central to Object-Oriented Programming (OOP). Used well, it provides hooks into an existing codebase where new functionality and behaviour can (relatively) easily be integrated into a proven, tested codebase.
Subtype inheritance can bring significant benefits, including easier integration, reduced regression test time and improved maintenance.
However, using virtual functions in C++ brings a runtime performance overhead. This overhead may appear inconsequential for individual calls, but in a non-trivial real-time embedded application, these overheads may build up and […]
Posted in C/C++ Programming, Design Issues
Tagged C++, design patterns, final, interface, Modern C++, Polymorphism
12 Comments
Understanding Arm Cortex-M Intel-Hex (ihex) files
Creating a flash image
The primary purpose of the ihex file in the embedded space is to create a file that is used to program/reprogram a target system. There are various file formats around, with the Intel Hex (ihex) format being among the most widely used.
The output of the linker stage of a build process is typically to generate a .elf file (Executable and Linkable Format). Many debuggers and programmers can work directly with the ELF file format. However, in many […]
Working with Strings in Embedded C++
In this post, by Embedded I’m generally referring to deeply embedded/bare-metal systems as opposed to Linux-based embedded systems.
Embedded systems and strings
Historically, the need for and thus the use of strings in embedded systems was fairly limited. However, this has changed with the advent of cheaper, full graphic displays and the growth of the ‘Internet of Things’ (IoT).
Many embedded systems sport full-colour graphics displays, supported by embedded-specific graphics libraries, including:
free open-source – e.g. LVGL
vendor-specific – e.g. TouchGFX from STMicroelectronics
fully specialised graphics […]
TDD in C with Ceedling and WSL2 – performance issues
Ceedling is still probably the best Test-Driven Development (TDD) environment for C programmers out there. But, as with many Free Open-Source Software ( FOSS ), tools getting it to work natively on a Windows environment involves the odd hoop-jumping exercise; either involving messing around with the likes of Cygwin or Mingw; or using a full Virtual Machine (VM) environment such as VirtualBox or VMware.
However, with the introduction of Windows-Subsystem-for-Linux (WSL) and the much-improved update to WSL2, running Linux centric FOSS […]
Posted in Build-systems, C/C++ Programming, Linux, Testing
Tagged C Declarations, C++, ceedling, TDD, Testing, WSL2
3 Comments
C++20 modules with GCC11
Introduction
One of the headline changes of the C++20 standard is the inclusion of modules. Modules promise to significantly change the structure of C++ codebases and possibly signal headers’ ultimate demise (but probably not in my lifetime). It also opens the door to potentially have a unified build system and package manager, similar to Rust’s Cargo package manager; though I imaging standardising a unified build system would be one bloody battle.
Pre-C++20 builds
If you want to start a heated debate on any […]
Modern Embedded C++ – Deprecation of volatile
Compiling the following, straightforward code:
volatile int x;
int main() {
x += 10;
}
https://godbolt.org/z/jq83vdvj5
Using g++ with the directive -std=c++17 builds without any warnings or errors. However, change the directive to -std=c++20, and the result is:
source>: In function ‘int main()’:
<source>:5:5: warning: compound assignment with ‘volatile’-qualified left operand is deprecated [-Wvolatile]
5 | x += 10;
| ~~^~~~~
Compiler returned: 0
The new C++ standard, C++20, has deprecated volatile! So, what […]
GitHub Codespaces and online development
In our previous posting, we discussed using VSCode’s Dev Container extension to allow running workspaces directly within a Docker container.
In December 2020, I was granted early access to a new feature developed by GitHub called Codespaces. Codespaces offers an online VSCode development environment, enabling you to develop entirely in the cloud.
The great news is that Codespaces uses the same core process, and file structure, as Dev Containers; meaning once we have our .devcontainer folder setup (if you are unfamiliar with […]
Posted in Agile, C/C++ Programming, General, Industry Analysis, Testing
Tagged Codespaces, docker, GitHub, GoogleTest, Meson, VSCode
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VSCode, Dev Containers and Docker: moving software development forward
Long term readers of this blog will know our devotion to using container-based technology, especially Docker, to significantly improve software quality through repeatable builds.
In the Autumn/fall of 2020, Microsoft introduced a Visual Studio Code (VSCode) extension Remote – Containers. With one quick stroke, this extension allows you to open a VSCode project within a Docker container.
Getting started with Dev Containers and Docker
There are several different approaches to using Dev Containers. In this post, we shall cover three options:
Using an existing […]
Posted in Agile, C/C++ Programming, Testing
Tagged C++, devcontainer, docker, GoogleMock, GoogleTest, Meson, ninja, VSCode
1 Comment
Introduction to the ARM® Cortex®-M7 Cache – Part 3 Optimising software to use cache
Part 1 Cache Basics
Part 2 Cache Replacement Policy
Caches – Why do we miss?
Cold Start
As stated, both data and instruction caches are required to be invalidated on system start. Therefore, the first load of any object (code or data) cannot be in cache (thus the cold start condition).
One available technique to help with cold-start conditions is the ability to pre-load data into the cache. The ARMv7-M instruction set adds the Preload Data (PLD) instruction. The PLD instruction signals to the memory […]