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irq0_interrupt_income:
mov al, 20h
out 20h, al

cmp byte [tasknumber], 0
je run0task
inc byte [tasknumber]
jmp dword 0x40:0x0 ;run task1
run0task:
mov byte [tasknumber], 0
jmp dword 0x48:0x0 ;run task 2

iretd

BMW wrote:Do you even know assembly, or BBCode?

I dont[sic] understand ?

pseudo-code

But i[sic] have noticed that it's working wrong i[sic] can't debugg[sic] it becouse[sic] bochs dont[sic] break point[sic] for itq0[sic] interrupts but it seems like only 1 interrupt income[sic]

mov 20h, al

Combuster wrote:

I dont[sic] understand ?

But you edited nonetheless.

pseudo-code

Is the real code so much bigger that it matters? That might also be the error.

But i[sic] have noticed that it's working wrong i[sic] can't debugg[sic] it becouse[sic] bochs dont[sic] break point[sic] for itq0[sic] interrupts but it seems like only 1 interrupt income[sic]

don't, no space before punctuaton, I (the capital letter), missing punctuation, I, debug, because, doesn't, breakpoint, IRQ0, was received. It rather looks like English is your biggest enemy right now. That or you're too lazy to do any form of writing correctly - text or code.
That aside, this actually is a frequently asked question: FAQ - so maybe you should be more careful in doing what it says.

Code: Select all

mov 20h, al

From now on, all instances of number 20 are to have a different meaning?


Now, could you please sanitize everything so that we aren't wasting time trying to figure out what garbage is real and which isn't?

    section .data
currentTSSfarPointer:
    dd 0                           ;Note: CPU ignores the "offset" part, so there's not much point having it..
currentTSS:
    dw 0x38
    section .text


;Note: IRQ0 *must* be an "interrupt gate" (and can not be a "trap gate")

irq0_interrupt_service:
    push eax

    ;send eoi signal (end of interrupt)
    mov al, 0x20
    out 0x20, al   

    add word [currentTSS],8        ;Get next TSS to switch to
    cmp word [currentTSS],0x38     ;Is it too high?
    jbe .l1                        ; no
    mov word [currentTSS],0x30     ; yes, wrap around to first TSS
.l1:
    jmp far [currentTSSfarPointer] ;WARNING: Task switch and not a JMP (execution continues after the jump)

    pop eax
    iretd

ManyGifts wrote:So let's have an exmaple:

Code: Select all

    section .data
currentTSSfarPointer:
    dd 0                           ;Note: CPU ignores the "offset" part, so there's not much point having it..
currentTSS:
    dw 0x38
    section .text


;Note: IRQ0 *must* be an "interrupt gate" (and can not be a "trap gate")

irq0_interrupt_service:
    push eax

    ;send eoi signal (end of interrupt)
    mov al, 0x20
    out 0x20, al   

    add word [currentTSS],8        ;Get next TSS to switch to
    cmp word [currentTSS],0x38     ;Is it too high?
    jbe .l1                        ; no
    mov word [currentTSS],0x30     ; yes, wrap around to first TSS
.l1:
    jmp far [currentTSSfarPointer] ;WARNING: Task switch and not a JMP (execution continues after the jump)

    pop eax
    iretd

My problem is that
jmp far [currentTSSfarPointer] ;WARNING: Task switch and not a JMP (execution continues after the jump)

ManyGifts wrote:Seems to be false, because it seems like it does not continue after jump instruction and IRETD instruction is not executed. Also irq0 procedure is not executed no more...

Brendan wrote:Hi,

ManyGifts wrote:So let's have an exmaple:

Code: Select all

    section .data
currentTSSfarPointer:
    dd 0                           ;Note: CPU ignores the "offset" part, so there's not much point having it..
currentTSS:
    dw 0x38
    section .text


;Note: IRQ0 *must* be an "interrupt gate" (and can not be a "trap gate")

irq0_interrupt_service:
    push eax

    ;send eoi signal (end of interrupt)
    mov al, 0x20
    out 0x20, al   

    add word [currentTSS],8        ;Get next TSS to switch to
    cmp word [currentTSS],0x38     ;Is it too high?
    jbe .l1                        ; no
    mov word [currentTSS],0x30     ; yes, wrap around to first TSS
.l1:
    jmp far [currentTSSfarPointer] ;WARNING: Task switch and not a JMP (execution continues after the jump)

    pop eax
    iretd

My problem is that
jmp far [currentTSSfarPointer] ;WARNING: Task switch and not a JMP (execution continues after the jump)

This "jmp" causes a task switch, where the address of the instruction after then "jmp" is stored in the "CS" and "EIP" fields of the current task's TSS, and then CS and EIP (and other stuff) is loaded from the TSS you're switching to. The next instruction the CPU executes will (hopefully) be whatever is at the "CS:EIP" stored in the TSS you switched to. Eventually (hopefully) something will cause a task switch back to your task, and your task will continue executing at whatever is at the "CS:EIP" stored in your task's TSS, which will be the address of the instruction after the "jmp" (which was stored in the TSS earlier by the "jmp" instruction).

Basically; "execution of this task will continue after the jump (when something switches back to this task)".

ManyGifts wrote:Seems to be false, because it seems like it does not continue after jump instruction and IRETD instruction is not executed. Also irq0 procedure is not executed no more...

That's because you never switch back to the task. I'd guess your code crashes before that happens.


Cheers,

Brendan

Gigasoft wrote:Did you remember to initialize EFLAGS in the second task's TSS so that the IF bit is set?