computer science

Indirect branch tracking

Indirect branch tracking is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Indirect branch tracking rather than just read about it. In short: Indirect branch tracking (IBT), also known as branch target identification (BTI), is a control flow integrity mechanism implemented on some Intel x86-64 and ARM-64 processors. IBT is designed to protect against computer security exploits that use indirect branch instructions to jump into code in unintended ways, such as return-oriented programming.

Key takeaways

Indirect branch tracking belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Indirect branch tracking to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Indirect branch tracking from memory before moving on to harder problems.

Reference excerpt

Indirect branch tracking (IBT), also known as branch target identification (BTI), is a control flow integrity mechanism implemented on some Intel x86-64 and ARM-64 processors. IBT is designed to protect against computer security exploits that use indirect branch instructions to jump into code in unintended ways, such as return-oriented programming. It creates a special "branch target" instructions that have no function other than to mark a location as a valid indirect branch target, with the processor capable of being put into a mode where it will raise an exception if an indirect branch is made to a location without a branch target instruction.

Implementations On Intel processors, the technique is known as Indirect Branch Tracking (IBT), with the "end branch" instructions endbr32 and endbr64 acting as the branch target instructions for 32- and 64-bit mode respectively. IBT is part of the Intel Control-Flow Enforcement Technology first released in the Tiger Lake generation of processors. The similar technology on ARM-64 processors is called Branch Target Identification (BTI), with the instruction, also called BTI, having three variants that make it check only for jumps, or function calls, or for both.

References

Worked examples

Example 1 — a first encounter with Indirect branch tracking

Start with the simplest possible case. Write down what Indirect branch tracking claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Indirect branch tracking before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Indirect branch tracking ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Indirect branch tracking

In research: Indirect branch tracking appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Indirect branch tracking in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Indirect branch tracking is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer security, Computer security stubs, Control flow integrity, so understanding it makes those chapters shorter.
In everyday life: Look for Indirect branch tracking outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Indirect branch tracking in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Indirect branch tracking means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Indirect branch tracking out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Indirect branch tracking in simple terms?

Why does Indirect branch tracking matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Indirect branch tracking?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Indirect branch tracking.