Code: Select all

Немного модифицированный код из L4 
    __asm__ __volatile__(
    "lgdt %0          \n\t"
    "ljmp %1,$1f      \n\t "  /* refetch code segment descr.  */
    ".align 4         \n\t"
    "1:               \n"     /* by jumping across segments */
    :: "m"(gdt_desc), "i" (sel_os_code) );

    /* set the segment registers from the freshly installed GDT
       and load the Task Register with the TSS via the GDT */

    __asm__ __volatile__(
    "mov  %0, %%ds      \n\t" /* reload data segment      */
    "mov  %0, %%es      \n\t" /* need valid %es for movs/stos */
    "mov  %1, %%ss      \n\t" /* reload stack segment     */
    "mov  %2, %%gs      \n\t" /* load TLS segment         */
    "mov  %0, %%fs      \n\t" /* default                         */
    "xor %%eax, %%eax   \n\t" /*              */
    "lldt %%ax          \n\t" /* clear LDTR           */
    :
    : "r"(sel_app_data), "r"(sel_os_stack), "r"(sel_ostls)
    : "eax" );

    __asm__ __volatile__(
    "ltr %%ax \n\t"
    ::"a"(sel_tss));

Code: Select all

static inline void outb(const uint16_t port, const uint8_t val)
{
    __asm__ __volatile__ ("outb %0, %w1" : : "a"(val), "dN"(port));
}

void init_pic()
{
    outb(0x20, 0x11);
    outb(0xA0, 0x11);

    outb(0x21, 0x20);
    outb(0xA1, 0x28);

    outb(0x21, 0x04);
    outb(0xA1, 0x02);

    outb(0x21, 0x01);
    outb(0xA1, 0x01);

    outb(0xA1, 0xFF);
    outb(0x21, 0xFF);
};

компилируется в 

                 public _init_pic
 _init_pic       proc near
                 mov     al, 11h
                 out     20h, al         ; Interrupt controller, 8259A.
                 out     0A0h, al        ; PIC 2  same as 0020 for PIC 1
                 mov     al, 20h ; ' '
                 out     21h, al         ; Interrupt controller, 8259A.
                 mov     al, 28h ; '('
                 out     0A1h, al        ; Interrupt Controller #2, 8259A
                 mov     al, 4
                 out     21h, al         ; Interrupt controller, 8259A.
                 mov     al, 2
                 out     0A1h, al        ; Interrupt Controller #2, 8259A
                 mov     al, 1
                 out     21h, al         ; Interrupt controller, 8259A.
                 out     0A1h, al        ; Interrupt Controller #2, 8259A
                 mov     al, 0FFh
                 out     0A1h, al        ; Interrupt Controller #2, 8259A
                 out     21h, al         ; Interrupt controller, 8259A.
                 retn
 _init_pic       endp