Arm Barriers 101: Part #4: Speculation and break-before-make

Name: Arm Barriers 101: Part #4: Speculation and break-before-make
Rating: 5.0 (3 reviews)

Defending against Spectre/Meltdown and performing break-before-make sequences.

Created byAsh Wilding

Last updated 5/2025

English

What you'll learn

Discover how speculative side-channel attacks like Spectre and Meltdown work.
Explore how to use barriers to control speculation.
Investigate some of the nasty, horrible-to-debug issues that can occur when making certain modifications to the page tables.
Learn how to use barriers and break-before-make sequences to prevent these issues from occurring.

Course content

1 section • 5 lectures • 2h 53m total length

Introduction to Spectre and Meltdown32:58
Links mentioned in the video:
archadept.link/inferb
Papers mentioned in the video:
The original Spectre and Meltdown papers: https://spectreattack.com
Formalising and standardising the naming conventions used for speculative side-channel attacks: https://www.usenix.org/system/files/sec19-canella.pdf
Arm's whitepaper in response to Spectre and Meltdown: https://developer.arm.com/documentation/102816/latest/
Arm's whitepaper in response to Straight-line Speculation (co-authored by me ?): https://developer.arm.com/documentation/102825/latest/
Controlling speculation through barriers40:56
Break-before-make sequences30:31
Quiz20:22
Barriers 101 full course revision session48:36

Requirements

Beginner friendly!
Assumes no prior Arm Architecture experience.
Some basic C/C++ programming experience is recommended, but not required.
Strongly recommended to take our "Arm Barriers 101: Part #3: Expanding our toolkit" course first.

Description

Welcome to Part 4 of our Barriers 101 training course, a comprehensive deep dive on barriers in the Arm® Architecture.

This course is suitable for software engineers working on Arm-based platforms on system-level software, from down at the firmware layer all the way up through to the kernel, hypervisor, and device drivers.

In these lessons, you'll learn:

How speculative side-channel attacks like Spectre and Meltdown work.
How we can use barriers to control speculation and to defend against these kinds of attacks.
How failing to correctly perform break-before-make sequences when making certain modifications to the page tables may lead to all sorts of nasty, horrible-to-debug issues.
How to use barriers to correctly perform such sequences.

From beginner to expert: Our courses are suitable for all levels of experience, whether you're already a seasoned veteran of the Arm Architecture or you're seeing Arm Barriers for the very first time.

How it really works: Our courses go both broader and deeper on the topic of barriers than anyone else; we show you how things really work, and more importantly, why.

Learning is doing: Reinforce your learning with 30 multiple-choice quiz questions including a video walkthrough of each question and answer, followed by a full course revision session touching on every lesson from all four parts of the entire Barriers 101 training course.

Recognised trainer: Our courses are written and produced by Ash Wilding, formerly one of Arm's lead technical trainers and a kernel engineer at both Amazon AWS and Apple.

Who this course is for:

Engineers at all experience levels working on Arm-based platforms.
Firmware Engineers.
Kernel Engineers.
Hypervisor Engineers.
Device Driver Engineers.