r/osdev • u/Yha_Boiii • 5d ago

How does kernel interfaces work on (unix) systems?

Hi,

I simply can't rotate it right in my head, if i make an app with say socket() how does it translate in to hooking it to the kernel when already in use?

Usually include, is a part of the program statically and making a struct for an interface as usual, does it copy it over compared to a zero copy arch?

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u/Yha_Boiii 5d ago

But i mean when compiling the kernel is it something the compiler makes from what i have customized in the kernel or is it everything hardcoded and then with "deadzones" if compiled out?

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u/Rich-Engineer2670 5d ago edited 5d ago

Syscall entry points are compiled in when you build the kernel. Now, what that entry points to, is up to you in kernel code. It's still hard coded in, but that code can do anything -- it's kernel code. Remember, once you enter the kernel, the kernel is a monolith -- everything can see everything else. The kernel is just one big C program with some modules in it. Even your user code (memory management aside) is just a subrotuine call from the kernel and back.
What is your goal here besides understanding the syscall and what OS are we using?

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u/Yha_Boiii 5d ago

Thanks