Comments for "https://os.phil-opp.com/double-fault-exceptions/"

[utterances-bot]

This is a general purpose comment thread for the “Double Faults” post.

[pbn4]

Awesome stuff, waiting for more :)

[phil-opp]

@pbn4 Thank you :)

[mtn]

This is awesome -- thank you for the amazing work @phil-opp!

I had a newbie question: I understand why these handlers are useful in preventing everything from ending up in a restart loop, but differences would an actual implementation have? For example, if a user is running a program that results in a page fault in their shell, the handler must be reporting that back to the application so it can surface it to the user, right?

[phil-opp]

@mtn Thank you!

I understand why these handlers are useful in preventing everything from ending up in a restart loop, but differences would an actual implementation have?

Depends on the OS implementation and the fault type. For example, if the exception is caused because a userspace process tried to execute a privileged instruction, the kernel would simply kill the process (and the shell would report to the user that the process was killed).

For a page fault, the kernel can react in multiple ways. If it's just an out of bound access to unmapped memory (like we do in the blog post), the kernel would kill the user program with a segmentation fault. However, most operating systems have a mechanism called swapping, where parts of the memory are moved to disk when the main memory becomes too full. Then a legitimate memory access could cause a page fault because the accessed data is no longer in memory. The OS can handle this page fault by loading the contents of the memory page from disk and continuing the interrupted process. This technique is called demand paging and allows to run programs that wouldn't fit completely into memory.

[yjhmelody]

Yeah! That you showed for us is what we have learned from OS course.

[montao]

Thanks for the post, Phil. I am going to catch up on your posts now that I have completed a B.Sc. in technology. I am going to continue for a master in computer science and your material is very helpful for understanding operating systems.

Small typo maybe: You spell it 0xdeadbeaf but the common spelling is usually 0xdeadbeef isn't it?

[phil-opp]

@montao Congratulations on your degree!

Small typo maybe: You spell it 0xdeadbeaf but the common spelling is usually 0xdeadbeef isn't it?

Thanks! Fixed in f551116.

Where should I go next after completing your tutorial ? I am neither a beginner nor an expert in Rust but I am interested in OS development and have followed your tutorial thoroughly, I would like to proceed further

Thanks for making this series :)

[robert-w-gries]

@siddharthsymphony The OSDev Wiki is one of the best online resources for OS development. If you want more theoretical knowledge, take a look at Modern Operating Systems by Andrew Tanenbaum

[bacharSalleh]

@siddharthsymphony I'm very interesting in System Development, any resources you recommend beside The OSDev Wiki and Modern Operating Systems by Andrew Tanenbaum ?

[tnargy]

@phil-opp I’ve really enjoyed your blog! The way you express the concepts makes it easy for me to follow. Are you still planning on handling interrupts from external devices in next post?

[phil-opp]

@tnargy Thank you! Yes, the next post will be about hardware interrupts. It will explore the programmable interrupt controller, timer interrupts, and keyboard interrupts. I already created a first draft that you can preview here (it's still work in progress).

[Ben-PH]

Awesome stuff.

What was your source for learning this? If I wanted to contribute to the next posts while I'm having a go at them, do you have any recommended reading for that?