path: root/arch/x86_64/gdt.c

#include "arch/x86_64/gdt.h"
#include "arch/x86_64/tss.h"
#include "arch/processor.h"
#include "string.h"
#include "print.h"

static gdt_t s_baseline_gdt =
{
    { 0 },  /* Kernel NULL */
    {       /* Kernel Code (64-bit RO EX DPL0) */
        .limit_0_15 = 0xFFFF,
        .base_0_15 = 0,
        .base_16_23 = 0,
        .type = CD_SEGMENT_TYPE_CODE | CD_SEGMENT_TYPE_WRITEABLE,
        .s = 1,
        .dpl = 0,
        .p = 1,
        .limit_16_19 = 0xF,
        .avl = 0,
        .l = 1,
        .d_b = 0,
        .g = 1,
        .base_24_31 = 0
    },
    {       /* Kernel Data (64-bit RW DPL0) */
        .limit_0_15 = 0xFFFF,
        .base_0_15 = 0,
        .base_16_23 = 0,
        .type = CD_SEGMENT_TYPE_WRITEABLE,
        .s = 1,
        .dpl = 0,
        .p = 1,
        .limit_16_19 = 0xF,
        .avl = 0,
        .l = 0,
        .d_b = 1,
        .g = 1,
        .base_24_31 = 0
    },
    { 0 },  /* User NULL */
    {       /* User Data (64-bit RO EX DPL3)*/
        .limit_0_15 = 0xFFFF,
        .base_0_15 = 0,
        .base_16_23 = 0,
        .type = CD_SEGMENT_TYPE_WRITEABLE,
        .s = 1,
        .dpl = 3,
        .p = 1,
        .limit_16_19 = 0xF,
        .avl = 0,
        .l = 0,
        .d_b = 1,
        .g = 1,
        .base_24_31 = 0,
    },
    {       /* User Code (64-bit RO EX DPL3)*/
        .limit_0_15 = 0xFFFF,
        .base_0_15 = 0,
        .base_16_23 = 0,
        .type = CD_SEGMENT_TYPE_CODE | CD_SEGMENT_TYPE_WRITEABLE,
        .s = 1,
        .dpl = 3,
        .p = 1,
        .limit_16_19 = 0xF,
        .avl = 0,
        .l = 1,
        .d_b = 0,
        .g = 1,
        .base_24_31 = 0,
    },
    {       /* TSS Low */
        .limit_0_15 = 0,
        .base_0_15 = 0,
        .base_16_23 = 0,
        .type = S_SEGMENT_TYPE_TSS_AVAIL,
        .avl = 0,
        .s = 0,
        .dpl = 0,
        .p = 1,
        .limit_16_19 = 0,
        .l = 0,
        .d_b = 0,
        .g = 0,
        .base_24_31 = 0,
    },
    { 0 }
};

void
gdt_setup(processor_t *proc)
{
    memcpy(proc->_gdt, s_baseline_gdt, sizeof(gdt_t));
    proc->_gdtr = (struct XDTR) {
        .length = sizeof(gdt_t) - 1,
        .address = (uintptr_t)&proc->_gdt
    };
    klogf("Processor %i GDT %#016X L%i\n", proc->id, proc->_gdt, proc->_gdtr.length);
}

void
tss_setup(processor_t *proc)
{
    segment_descriptor_t *tss_lo = &proc->_gdt[GDT_SEGMENT_TSS_LOW];
    segment_descriptor_t *tss_hi = &proc->_gdt[GDT_SEGMENT_TSS_HIGH];
    uintptr_t tssb = (uintptr_t)&(proc->_tss);
    tss_lo->base_0_15 = tssb & 0xFFFF;
    tss_lo->base_16_23 = (tssb >> 16) & 0xFF;
    tss_lo->base_24_31 = (tssb >> 24) & 0xFF;
    tss_hi->limit_0_15 = (tssb >> 32) & 0xFFFF;
    tss_hi->base_0_15 = (tssb >> 48) & 0xFFFF;

    size_t tssl = sizeof(struct TSS) - 1;
    tss_lo->limit_0_15 = tssl & 0xFFFF;
    tss_lo->limit_16_19 = (tssl >> 16) & 0xF;

    proc->_tss.iobp = sizeof(struct TSS);
}

void
tss_set_rsp(struct TSS *tss, uint8_t dpl, uintptr_t rsp)
{
    tss->rsp[dpl][0] = rsp & 0xFFFFFFFF;
    tss->rsp[dpl][1] = (rsp >> 32) & 0xFFFFFFFF;
}