StackOverflow2013

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PO(Writing kernel) How do I modify the interrupt descriptor table?
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copied!<p>I am writing a small kernel just to poke around the low level stuff a bit. Right now, it boots in Virtual Box and I can display text to the screen, allocate some memory, and other really basic things. It's written in C++ and a little asm.</p> <p>One of the things I wanted to explore was the mechanism behind multi-tasking. As I understand it, it goes something like this:</p> <ol> <li>The kernel initializes the Interrupt Descriptor Table so that an interrupt is issued periodically (e.g. a millisecond) and calls a routine defined in the kernel.</li> <li>When the routine is called, it can decide to set the code/data segments and stack pointer to those of another program's context, a "context-switch."</li> </ol> <p>So, it seemed simple in concept, but I knew the details were going to be a lot hairier. I've found a few things on line, but the terminology varies a lot, and the examples seem to be from contexts I don't have (like from within the Linux kernel).</p> <p>However, the way to set the descriptor tables seems to be like this:</p> <ol> <li>Send some data to the PIC (<code>outb</code> and what-not) to initialize it.</li> <li>Prepare an interrupt table in memory, with function pointers to the routines you want, being careful that the functions are capable of being signal handlers.</li> <li>Load the table with <code>lidt</code>.</li> </ol> <p>However, I can't find much on specifically doing these things, or whether this is even correct. Does anyone have resources for a bewildered kernel writer?</p>

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