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I'm trying to reuse de bios interrupt 0x13. I switch protected mode to real mode (http://wiki.osdev.org/Real_Mode) and then I put into the registers de correct value. After that I call the interruption.

But when the bochs(emulator that i'm using) executes the instruction: lidt idt_48; It go crazy. The next instructions do not correspond with the code.
For example, the next one of lidt is mov bp, 0x0133.

What can be wrong?

Code that I'm trying to execute: Thanks!

As you have discovered, you can't call BIOS functions from protected mode. You really need to write your own driver.

I am switching the mode

movl $0x011, %eax;
movl %eax,%cr0;

Do you know that you're modifying up to 32 bits, and that changing 90% of those bits is actually not what you want, whereas the bits you want to change according to the description are actually wrong?

lidt idt_48; It go crazy. The next instructions do not correspond with the code.
For example, the next one of lidt is mov bp, 0x0133.

I would also expect that

mov $0x18,%ax;

actually accesses EAX because you didn't tell the assembler to switch the encoding from 16 to 32 bits.

movl $0x011, %eax;
movl %eax,%cr0;

Do you know that you're modifying up to 32 bits, and that changing 90% of those bits is actually not what you want, whereas the bits you want to change according to the description are actually wrong?

The result it's the same as andl. I use less instructions.

lidt idt_48; It go crazy. The next instructions do not correspond with the code.
For example, the next one of lidt is mov bp, 0x0133.

I would also expect that

mov $0x18,%ax;

actually accesses EAX because you didn't tell the assembler to switch the encoding from 16 to 32 bits.

The segment registers have 16 bits. I use the low part of the register that is 0x0018.

When loading CR0 you must preserve reserved bits. You don't do so.

When you load 0 to CR0, completely ignoring the reserved bits, you may think that you are returning to real mode. What you think and what actually happens may not coincide. A debugging session might help here; better still, just change the bit(s) that you want to and preserve the others.

Undefined behaviour is rarely good news.

I change this and It isn't still working.

As most people take the easy way out and write their own driver, I suspect that you are going to have to debug this one yourself. Single-step the code until you call the interrupt and see if memory and registers look correct. In particular, check that any structures required by real-mode BIOS calls haven't been changed. An obvious place to check is that the interrupt vectors are still as the BIOS set them.

dunedain1990 wrote:I change this and It isn't still working.

Why does my crystal ball say you guessed a change and didn't actually fix anything...?