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/*
 * Copyright (C) 2001-2004 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <arch/pm.h>
#include <config.h>
#include <arch/types.h>
#include <typedefs.h>
#include <arch/interrupt.h>
#include <arch/asm.h>
#include <arch/context.h>
#include <panic.h>

/*
 * Early ia32 configuration functions and data structures.
 */

/*
 * We have no use for segmentation so we set up flat mode. In this
 * mode, we use, for each privilege level, two segments spanning the
 * whole memory. One is for code and one is for data.
 */
struct descriptor gdt[GDT_ITEMS] = {
    /* NULL descriptor */
    { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
    /* KTEXT descriptor */
    { 0xffff, 0, 0, AR_PRESENT | AR_CODE | DPL_KERNEL, 0xf, 0, 0, 1, 1, 0 },
    /* KDATA descriptor */
    { 0xffff, 0, 0, AR_PRESENT | AR_DATA | AR_WRITABLE | DPL_KERNEL, 0xf, 0, 0, 1, 1, 0 },
    /* UTEXT descriptor */
    { 0xffff, 0, 0, AR_PRESENT | AR_CODE | DPL_USER, 0xf, 0, 0, 1, 1, 0 },
    /* UDATA descriptor */
    { 0xffff, 0, 0, AR_PRESENT | AR_DATA | AR_WRITABLE | DPL_USER, 0xf, 0, 0, 1, 1, 0 },
    /* TSS descriptor - set up will be completed later */
    { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }
};

static struct idescriptor idt[IDT_ITEMS];

static struct tss tss;

struct tss *tss_p = NULL;

/* gdtr is changed by kmp before next CPU is initialized */
struct ptr_16_32 gdtr __attribute__ ((section ("K_DATA_START"))) = { .limit = sizeof(gdt), .base = KA2PA((__address) gdt) };
struct ptr_16_32 idtr __attribute__ ((section ("K_DATA_START"))) = { .limit = sizeof(idt), .base = KA2PA((__address) idt) };

void gdt_setbase(struct descriptor *d, __address base)
{
        d->base_0_15 = KA2PA(base) & 0xffff;
        d->base_16_23 = (KA2PA(base) >> 16) & 0xff;
        d->base_24_31 = (KA2PA(base) >> 24) & 0xff;
}

void gdt_setlimit(struct descriptor *d, __u32 limit)
{
        d->limit_0_15 = limit & 0xffff;
        d->limit_16_19 = (limit >> 16) & 0xf;
}

void idt_setoffset(struct idescriptor *d, __address offset)
{
    d->offset_0_15 = KA2PA(offset) & 0xffff;
    d->offset_16_31 = KA2PA(offset) >> 16;
}

void tss_initialize(struct tss *t)
{
    memsetb((__address) t, sizeof(struct tss), 0);
}

/*
 * This function takes care of proper setup of IDT and IDTR.
 */
void idt_init(void)
{
    struct idescriptor *d;
    int i;
    
    for (i = 0; i < IDT_ITEMS; i++) {
        d = &idt[i];

        d->unused = 0;
        d->selector = selector(KTEXT_DES);

        d->access = AR_PRESENT | AR_INTERRUPT;  /* masking interrupt */

        if (i == VECTOR_SYSCALL) {
            /*
             * The syscall interrupt gate must be calleable from userland.
             */
            d->access |= DPL_USER;
        }
        
        idt_setoffset(d, ((__address) interrupt_handlers) + i*interrupt_handler_size);
        trap_register(i, null_interrupt);
    }
    trap_register(13, gp_fault);
    trap_register( 7, nm_fault);
    trap_register(12, ss_fault);
}


void pm_init(void)
{
    struct descriptor *gdt_p = (struct descriptor *) gdtr.base;

    /*
     * Each CPU has its private GDT and TSS.
     * All CPUs share one IDT.
     */

    if (config.cpu_active == 1) {
        idt_init();
        /*
         * NOTE: bootstrap CPU has statically allocated TSS, because
         * the heap hasn't been initialized so far.
         */
        tss_p = &tss;
    }
    else {
        tss_p = (struct tss *) malloc(sizeof(struct tss));
        if (!tss_p)
            panic("could not allocate TSS\n");
    }

    tss_initialize(tss_p);
    
    gdt_p[TSS_DES].access = AR_PRESENT | AR_TSS | DPL_KERNEL;
    gdt_p[TSS_DES].special = 1;
    gdt_p[TSS_DES].granularity = 1;
    
    gdt_setbase(&gdt_p[TSS_DES], (__address) tss_p);
    gdt_setlimit(&gdt_p[TSS_DES], sizeof(struct tss) - 1);

    /*
     * As of this moment, the current CPU has its own GDT pointing
     * to its own TSS. We just need to load the TR register.
     */
    __asm__("ltr %0" : : "r" ((__u16) selector(TSS_DES)));
}