Immunity Aware Programming facts for kids

Immunity aware programming is a special way of writing the instructions, called firmware, for electronic devices. Think of firmware as the basic software that makes a gadget like a smartphone or a game console work. This special programming helps these devices deal with unexpected problems that can make them crash or act strangely.

These problems can happen in the device's main brain, the CPU, or its memory, called RAM. They might be caused by tiny energy zaps from space (called single event upsets), not enough power, or even strong signals from other electronic devices nearby. Immunity aware programming helps the "victim" device stay reliable and keep working, even when these errors try to mess things up.

Most of these techniques focus on making the software in the "victim" device super reliable. A few techniques also help the "source" device (the one causing interference) send out less unwanted noise. Because of this, Immunity aware programming is a type of:

• Defensive programming (making software strong against errors).
• EMC Aware Programming (making software work well with electromagnetic signals).

Why Devices Need a "Shield"

Electronic devices, especially small ones like those in your phone or a smart home gadget, are amazing. But they can be sensitive. Imagine a tiny, invisible zap of energy hitting a computer chip. This zap could flip a tiny switch inside the chip, changing a "0" to a "1" or vice-versa. This small change can cause a big problem, like making an app crash or a device stop responding.

What Causes These Problems?

Several things can cause these unexpected errors:

• Space Zaps: Tiny particles from space, like cosmic rays, can hit computer chips and cause a "single event upset". It's like a tiny, random glitch.
• Power Problems: If a device doesn't get enough power, or if the power flickers, its electronic parts might not work correctly.
• Invisible Noise: Other electronic devices, like a microwave or a radio, can send out invisible electromagnetic signals. These signals can sometimes interfere with nearby gadgets, causing errors.

These problems are often random and hard to predict. Immunity aware programming is all about preparing for these unexpected glitches and making sure the device can either ignore them or fix itself quickly.

How Immunity Aware Programming Works

Immunity aware programming uses clever tricks in the software to make devices more robust. It's like building extra safety nets and backup plans into the code.

Making Software More Reliable

One main goal is to make the software in the "victim" device super reliable. This means the program can detect when something goes wrong and either correct it or keep running without crashing.

Duplicating Important Information

One simple trick is to duplicate important information or instructions. For example, if a device needs to know a specific number, the program might store that number twice. If one copy gets corrupted by an error, the program can check the other copy.

C sample code: function parameter duplication.

C sample code: duplication of test conditions.

Checking and Re-checking

The software can also be designed to check its own work. After doing a calculation, it might do the calculation again to make sure the answer is the same. If the answers don't match, it knows an error happened and can try to fix it or restart.

Branch duplication.

Smart Error Handling

Instead of just crashing, an immunity-aware program has special "error handlers." If it detects a problem, it can jump to a specific part of the code designed to deal with errors. This might involve restarting a small part of the system or trying the operation again.

Program memory filled with code, NOPs, and error handler.

Controlling the Flow

Sometimes, programs use special "tokens" or signals to make sure that different parts of the code run in the correct order. If a token goes missing or gets corrupted, the program knows something is wrong.

Token passing as execution flow control.

C source: token passing with global function ID.

C source: token passing with function parameters.

Reducing Interference from "Source" Devices

While most techniques focus on the "victim" device, some also help "source" devices. If a device is known to create a lot of electromagnetic noise, its software can be designed to reduce that noise. This helps prevent it from causing problems for other devices nearby.

Why is This Important?

Immunity aware programming is super important for devices where reliability is key. Imagine a medical device, a car's computer, or even a satellite. If these devices crash due to a random error, the consequences could be serious. By making software more robust, engineers can build devices that are safer and more dependable. It helps ensure that our gadgets work when we need them most, even in challenging environments.

Hard- and software combination: detection of power supply fluctuation using an AD-converter.

Images for kids

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  Cause and effect figure. The cause must be determined, so the problem can be fixed.

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  Token passing as execution flow control

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  C source: token passing with global function ID.

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  C source: token passing with function parameters

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  Program memory filled with code, NOPs, and error handler

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  Memory before and after the implementation of both function token and NOP-Fills

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  An experimental analysis of CPU time overhead and the amount of duplicated variables

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  C sample code: function parameter duplication

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  C sample code: duplication of test conditions

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  Branch duplication

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  Hard- and software combination: detection of power supply fluctuation using an AD-converter