More Tripple Faults

[srg]

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[jrfritz]

Probly because your IDT is bad...Perica has a good asm IDT......but i'm looking at your code....

[Pype.Clicker]

Code: Select all

        ; Now patch the IDT Entries
       mov ecx, 47
                 mov bx, [IDT_location + 2]
.IDT_Patch       mov ax, [linear_cs]
                 add word [bx], ax 
                 add bx, 8
       loop .IDT_Patch
       

seems weird to me. First because you shouldn't use the relocated (physical) mov bx,[IDT_location] value, but rather directly lea bx,[IDT].
Second, you should take care of the case when add word[bx],ax would overflow and perform adc [bx+6],0 aswell.

[srg]

I have changed it to this to get rid of over flow but I still get tripple faults




       ; Now patch the IDT Entries
       mov ecx, 47 ; Therea are 47 Ints
lea ebx, [IDT] ; Get the position of IDT
.IDT_Patch mov edx, [linear_cs] ; Get that value to patch with
xor eax, eax
       mov ax, word [ebx] ; Get current value
       add eax, edx ; Convert it to linear
       mov word [ebx], ax ; Set Value with lower half
       shr eax, 16 ; bring higher half into ax
       add ebx, 6 ; Go to the higher offset in Entry
mov word [ebx], ax ; set it
       add ebx, 2 ; Goto Next IDT Entry
       loop .IDT_Patch

[DarylD]

I would just use C to set up the descriptors, my c function is as follows:

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void Descriptor_SetInterruptGate( uint32 nInterrupt, void *pHandler ) {
    Kg_sKernel.m_sIDT[ nInterrupt ].m_nSelector = 0x08;
    Kg_sKernel.m_sIDT[ nInterrupt ].m_nBaseLow = ( ( uint32 ) pHandler ) & 0xFFFF;
    Kg_sKernel.m_sIDT[ nInterrupt ].m_nBaseHigh = ( ( uint32 ) pHandler ) >> 16;
    Kg_sKernel.m_sIDT[ nInterrupt ].m_nFlags = 0x8E00;
}

My IDT struct is as follows:

Code: Select all

typedef struct {
    uint16 m_nBaseLow;
    uint16 m_nSelector;
    uint16 m_nFlags;
    uint16 m_nBaseHigh;
}
K_sIDT_t;

I initially set them all up to point to a generic ISR that just prints out a message.

[Pype.Clicker]

I have changed it to this to get rid of over flow but I still get tripple faults

Code: Select all

        ; Now patch the IDT Entries
       mov ecx, 47                   ; Therea are 47 Ints
                 lea ebx, [IDT]                ; Get the position of IDT
.IDT_Patch       mov edx, [linear_cs]          ; Get that value to patch 
       ...
       loop .IDT_Patch

You're doing 47 iterations and each of them process one IDT entry! you should set ecx to ((IDT_end-IDT)/8)-1.

[srg]

Added that, but it still tripple faults!! >:(

[Pype.Clicker]

1. remember some exceptions require you to pop the error code from the stack before you IRET' them ...
2. remember also that directly returning from an exception is unlikely to solve it ... a "hlt" is more likely to help you for now
3. you cannot just change AL value in an interrupt and return. You *must* do a push eax / pop eax or you'll see eax's value changing randomly from your main program.
4. doing a memory read between setting CR0.PE=1 and setting DS to the data descriptor value is an subtle invokation of #GPF
5. you should CLI before you start all the pmode switching job ...
6. better try your interrupts work with INT 0x30 before you enable hardware interrupt requests again.

[jrfritz]

Also...make your exces print a message and cli/hlt so you can see if there is a GPF going on or a stack thing or whatever....

[srg]

Do the cli and sti Instructions only stop hardware Interrupts, or do they stop the exceptions as well?

[jrfritz]

I belive they only stop the ones you made....since I still get exceptions ( tripple fault ) when there are bugs in my kernel before I enable interrupts

[Pype.Clicker]

Do the cli and sti Instructions only stop hardware Interrupts, or do they stop the exceptions as well?

only hardware interrupt requests are affected by IF.
exceptions and software interrupts (INT nn) will still be handled.

[srg]

BTW, is my PIC remapping code OK? It's an asm rewrite of the one in the FAQ

[srg]

All my exception handlers now put a letter into the first byte of screen memory and then call a halt instruction. Also if they have an error code it's poped into eax.

The letter means I can reference it to the exception that called it.

But it tripple faults before I even get there.

I have tried with both calling an exception with the Int instruction and also using the sti instruction, but it just triple faults.

[Pype.Clicker]

that sounds more and more like a badly assembled bug ... i mean you might have some reference to the old CS-based offsets after you moved CS to be zero-based ...