gdt.h File Reference

#include "threads/loader.h"

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Functions
void	gdt_init (void)

Function Documentation

gdt_init()

void gdt_init

(

void

)

                {
    /* Initialize GDT. */
    struct segment_descriptor64 *tss_desc =
        (struct segment_descriptor64 *) &gdt[SEL_TSS >> 3];
    struct task_state *tss = tss_get ();
 
    *tss_desc = (struct segment_descriptor64) {
        .lim_15_0 = (uint64_t) (sizeof (struct task_state)) & 0xffff,
        .base_15_0 = (uint64_t) (tss) & 0xffff,
        .base_23_16 = ((uint64_t) (tss) >> 16) & 0xff,
        .type = 0x9,
        .s = 0,
        .dpl = 0,
        .p = 1,
        .lim_19_16 = ((uint64_t)(sizeof (struct task_state)) >> 16) & 0xf,
        .avl = 0,
        .rsv1 = 0,
        .g = 0,
        .base_31_24 = ((uint64_t)(tss) >> 24) & 0xff,
        .base_63_32 = ((uint64_t)(tss) >> 32) & 0xffffffff,
        .res1 = 0,
        .clear = 0,
        .res2 = 0
    };
 
    lgdt (&gdt_ds);
    /* reload segment registers */
    asm volatile("movw %%ax, %%gs" :: "a" (SEL_UDSEG));
    asm volatile("movw %%ax, %%fs" :: "a" (0));
    asm volatile("movw %%ax, %%es" :: "a" (SEL_KDSEG));
    asm volatile("movw %%ax, %%ds" :: "a" (SEL_KDSEG));
    asm volatile("movw %%ax, %%ss" :: "a" (SEL_KDSEG));
    asm volatile("pushq %%rbx\n"
            "movabs $1f, %%rax\n"
            "pushq %%rax\n"
            "lretq\n"
            "1:\n" :: "b" (SEL_KCSEG):"cc","memory");
    /* Kill the local descriptor table */
    lldt (0);
}

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