How do i appropiately load the IDT?

NunoLava1998 · Post by **NunoLava1998** » Wed Dec 21, 2016 4:13 am

I need to load the Interrupt Descriptor Table in my environment (x86/32bit, compiled with C++, made in C/C++, i686-elf, protected mode).

However, i don't find much code or documentation about loading the IDT in this mode, and i have no idea how to load the IDT in my environment.

How do i?

Possible required info:
LIDT: function is in the kernel, code from Inline Assembly/Examples.
IO_WAIT: function is in the kernel, code from Inline Assembly/Examples.
IRQ1 handler: functions are in the kernel, code from OSDev wiki and mostly myself

iansjack · Post by **iansjack** » Wed Dec 21, 2016 4:34 am

http://wiki.osdev.org/Interrupts

NunoLava1998 · Post by **NunoLava1998** » Wed Dec 21, 2016 5:51 am

iansjack wrote:http://wiki.osdev.org/Interrupts

That explains absolutely nothing about my question, i already know what interrupts are and how they work, what i need help with is just loading the IDT.

glauxosdever · Post by **glauxosdever** » Wed Dec 21, 2016 6:05 am

Hi,

Next time please search better. The article describing IDT is here.

Hope this helps.

Regards,
glauxosdever

NunoLava1998 · Post by **NunoLava1998** » Wed Dec 21, 2016 6:09 am

glauxosdever wrote:Hi,

Next time please search better. The article describing IDT is here.

Hope this helps.

Regards,
glauxosdever

Thank you,
i just have no idea how to insert the data into the LIDT instruction.

iansjack · Post by **iansjack** » Wed Dec 21, 2016 6:46 am

NunoLava1998 wrote:I already know what interrupts are and how they work.

Everything that you have posted so far indicates that that is not true.

The article I linked to, and the references in it, explain everything.

FusT · Post by **FusT** » Wed Dec 21, 2016 6:51 am

You should write an assembly routine (well, routine.. about 3 lines, actually) that takes a pointer to your IDTR struct (containing base and limit) and load that pointer using LIDT.

I'm not trying to sound mean or insult you, but if you can't figure out how to do this kind of very basic stuff than this is not (yet) the hobby for you.

iansjack · Post by **iansjack** » Wed Dec 21, 2016 6:54 am

There's rather more to it than that. First you have to write the interrupt handlers and then construct the IDT.

NunoLava1998 · Post by **NunoLava1998** » Wed Dec 21, 2016 7:02 am

iansjack wrote:There's rather more to it than that. First you have to write the interrupt handlers and then construct the IDT.

The ironic things is that i already made the interrupt handlers, i'm just trying to construct the IDT beacuse if i don't it triple faults.

FusT · Post by **FusT** » Wed Dec 21, 2016 7:05 am

Of course there's more to it than that, but there is extensive documentation in the above linked wiki articles about what the IDT should look like.
Also, since those articles were linked, I assume that OP has read them before attempting to actually load an IDT, and understands that it's not as simple as just loading a value into the IDTR and expecting it to work.

iansjack · Post by **iansjack** » Wed Dec 21, 2016 7:18 am

I'm afraid that everything that the OP has posted so far indicates that he has no understanding of hardware interrupts. Let's face it, if you understand about interrupts and the IDT, loading the register is absolutely trivial. It's just the same as with the GDT.

NunoLava1998 · Post by **NunoLava1998** » Wed Dec 21, 2016 7:22 am

iansjack wrote:I'm afraid that everything that the OP has posted so far indicates that he has no understanding of hardware interrupts. Let's face it, if you understand about interrupts and the IDT, loading the register is absolutely trivial. It's just the same as with the GDT.

Oh, thanks for pointing that out (same as GDT).

I meant software interrupts, by the way.

iansjack · Post by **iansjack** » Wed Dec 21, 2016 7:53 am

NunoLava1998 wrote:I meant software interrupts, by the way.

I realize that.

Unfortunately, when considering a keyboard driver, it is hardware interrupts that you need to understand.

NunoLava1998 · Post by **NunoLava1998** » Wed Dec 21, 2016 9:17 am

iansjack wrote:
NunoLava1998 wrote:I meant software interrupts, by the way.
I realize that.

Unfortunately, when considering a keyboard driver, it is hardware interrupts that you need to understand.

And i actually have already made code for hardware interrupts, the only things i don't know about interrupts is how to work with things like lidt, lgdt, etc., but nothing else.

crunch · Post by **crunch** » Wed Dec 21, 2016 10:12 am

Is your plan to just post about every single step in os development? Obviously you are not picking up on the fact that you MUST be able to read documentation and then be able to translate that into code.

There is no problem with asking questions. This stuff can be difficult to grasp. If you're getting stuck here, you're not going to make it much farther (without significant handholding) until you learn how to rtfm

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