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 Post subject: Problem with ISR handling
PostPosted: Fri Mar 15, 2019 12:44 pm 
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Joined: Wed Feb 13, 2019 3:07 pm
Posts: 20
When i get a page fault i get continuous printing error(https://ibb.co/1bPsH5Z), but i need a one print about a page fault.

(isr.c - https://github.com/s04v/locOS/blob/master/cpu/isr.c)
(interrupt.asm - https://github.com/s04v/locOS/blob/mast ... errupt.asm)


The code that cause a page fault, I wrote it just for test.
Code:
initialise_paging();
print_s("Hello, paging world!\n");

u32 *ptr = (u32*)0xA00000;
u32 do_page_fault = *ptr;
/* next code is not executed*/


How to fix it??


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 Post subject: Re: Problem with ISR handling
PostPosted: Fri Mar 15, 2019 1:07 pm 
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Joined: Sat Nov 22, 2014 6:33 pm
Posts: 556
Location: USA
Shvets04 wrote:
Code:
initialise_paging();
print_s("Hello, paging world!\n");

u32 *ptr = (u32*)0xA00000;
u32 do_page_fault = *ptr;
/* next code is not executed*/

Without looking at your code, I bet that it is a simple mistake of:
Code:
u32 *ptr = (u32*)0xA00000;

Has too many zeros....One too many.

Ben
- http://www.fysnet.net/osdesign_book_series.htm


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 Post subject: Re: Problem with ISR handling
PostPosted: Fri Mar 15, 2019 1:19 pm 
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Joined: Wed Feb 13, 2019 3:07 pm
Posts: 20
BenLunt wrote:
Shvets04 wrote:
Code:
initialise_paging();
print_s("Hello, paging world!\n");

u32 *ptr = (u32*)0xA00000;
u32 do_page_fault = *ptr;
/* next code is not executed*/

Without looking at your code, I bet that it is a simple mistake of:
Code:
u32 *ptr = (u32*)0xA00000;

Has too many zeros....One too many.

Ben
- http://www.fysnet.net/osdesign_book_series.htm


i wrote it especially for test.


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 Post subject: Re: Problem with ISR handling
PostPosted: Sat Mar 16, 2019 12:56 am 
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Joined: Fri Aug 26, 2016 1:41 pm
Posts: 414
Because you aren't rectifying the page fault when your interrupt handler is executed it will return back to the same instruction,fault again, and repeat the cycle continuously. If you get a page fault you could temporarily issue a `hlt` instruction. This will of course effectively stop your kernel since it is being done in an interrupt handler with interrupts off.


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 Post subject: Re: Problem with ISR handling
PostPosted: Sat Mar 16, 2019 1:23 am 
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Joined: Fri Aug 26, 2016 1:41 pm
Posts: 414
The tutorial on which some of your IRQ code is based on is flawed with regards to passing registers_t by value and not by reference. I've recently wrote a post on reddit about it (and a fix): https://www.reddit.com/r/osdev/comments ... _interrupt .This bug is also mentioned on OSDev wiki here: https://wiki.osdev.org/James_Molloy%27s ... pted_state


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