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Why do we have two modes in cpu(user and kernel) since we still can still easily harm computer with userland programs? (lemm.ee)

submitted 1 year ago* (last edited 1 year ago) by SmoothSurfer@lemm.ee to c/programming@beehaw.org

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I have never dug into low level things like cpu architectures etc. and decided to give it a try when I learned about cpu.land.

I already was aware of the existence of user and kernel mode but while I was reading site it came to me that "I still can harm my system with userland programs so what does it mean to switch user mode for almost everything other than kernel and drivers?" also we still can do many things with syscalls, what is that stopping us(assuming we want to harm system of course) from damaging our system.

[edit1]: grammar mistakes

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[–] nickwitha_k@lemmy.sdf.org 3 points 1 year ago

I'd say that the separation is not just about security. It's also about performance and stability through separation of duties. The kernelb does a lot of work that is but directly related to current activity in userland. A good portion of this is to keep hardware in a state where userland programs can reliably run without having to reimplement low level functionality.

Additionally, when it comes to performance, it's worth looking at monolith vs microkernels. It may seem counter-intuitive but, for general-purpose computing, monolithic kernels outperform microkernels by a wide margin. This is due to the near exponential increase in context switching that ends up being required by microkernels for the sorts of tasks needed for such use cases.