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* Copyright (c) 2008 Jakub Jermar
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* Copyright (c) 2005-2006 Ondrej Palkovsky
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* - The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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* There is no segmentation in long mode so we set up flat mode. In this
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* mode, we use, for each privilege level, two segments spanning the
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* whole memory. One is for code and one is for data.
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descriptor_t gdt[GDT_ITEMS] = {
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{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
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/* KTEXT descriptor */
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{ .limit_0_15 = 0xffff,
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.access = AR_PRESENT | AR_CODE | DPL_KERNEL | AR_READABLE,
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/* KDATA descriptor */
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{ .limit_0_15 = 0xffff,
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.access = AR_PRESENT | AR_DATA | AR_WRITABLE | DPL_KERNEL,
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/* UDATA descriptor */
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{ .limit_0_15 = 0xffff,
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.access = AR_PRESENT | AR_DATA | AR_WRITABLE | DPL_USER,
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/* UTEXT descriptor */
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{ .limit_0_15 = 0xffff,
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.access = AR_PRESENT | AR_CODE | DPL_USER,
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/* KTEXT 32-bit protected, for protected mode before long mode */
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{ .limit_0_15 = 0xffff,
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.access = AR_PRESENT | AR_CODE | DPL_KERNEL | AR_READABLE,
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/* TSS descriptor - set up will be completed later,
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* on AMD64 it is 64-bit - 2 items in table */
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{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
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{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
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/* VESA Init descriptor */
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{ 0xffff, 0, VESA_INIT_SEGMENT >> 12, AR_PRESENT | AR_CODE | DPL_KERNEL,
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idescriptor_t idt[IDT_ITEMS];
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ptr_16_64_t gdtr = {.limit = sizeof(gdt), .base = (uint64_t) gdt };
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ptr_16_64_t idtr = {.limit = sizeof(idt), .base = (uint64_t) idt };
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void gdt_tss_setbase(descriptor_t *d, uintptr_t base)
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tss_descriptor_t *td = (tss_descriptor_t *) d;
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td->base_0_15 = base & 0xffff;
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td->base_16_23 = ((base) >> 16) & 0xff;
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td->base_24_31 = ((base) >> 24) & 0xff;
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td->base_32_63 = ((base) >> 32);
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void gdt_tss_setlimit(descriptor_t *d, uint32_t limit)
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tss_descriptor_t *td = (tss_descriptor_t *) d;
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td->limit_0_15 = limit & 0xffff;
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td->limit_16_19 = (limit >> 16) & 0xf;
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void idt_setoffset(idescriptor_t *d, uintptr_t offset)
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* Offset is a linear address.
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d->offset_0_15 = offset & 0xffff;
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d->offset_16_31 = offset >> 16 & 0xffff;
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d->offset_32_63 = offset >> 32;
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void tss_initialize(tss_t *t)
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memsetb(t, sizeof(tss_t), 0);
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* This function takes care of proper setup of IDT and IDTR.
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for (i = 0; i < IDT_ITEMS; i++) {
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d->selector = gdtselector(KTEXT_DES);
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d->type = AR_INTERRUPT; /* masking interrupt */
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idt_setoffset(d, ((uintptr_t) interrupt_handlers) +
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i * interrupt_handler_size);
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/** Initialize segmentation - code/data/idt tables
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descriptor_t *gdt_p = (descriptor_t *) gdtr.base;
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tss_descriptor_t *tss_desc;
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* Each CPU has its private GDT and TSS.
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* All CPUs share one IDT.
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if (config.cpu_active == 1) {
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* NOTE: bootstrap CPU has statically allocated TSS, because
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* the heap hasn't been initialized so far.
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/* We are going to use malloc, which may return
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* non boot-mapped pointer, initialize the CR3 register
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* ahead of page_init */
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write_cr3((uintptr_t) AS_KERNEL->genarch.page_table);
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tss_p = (tss_t *) malloc(sizeof(tss_t), FRAME_ATOMIC);
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panic("Cannot allocate TSS.");
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tss_initialize(tss_p);
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tss_desc = (tss_descriptor_t *) (&gdt_p[TSS_DES]);
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tss_desc->present = 1;
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tss_desc->type = AR_TSS;
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tss_desc->dpl = PL_KERNEL;
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gdt_tss_setbase(&gdt_p[TSS_DES], (uintptr_t) tss_p);
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gdt_tss_setlimit(&gdt_p[TSS_DES], TSS_BASIC_SIZE - 1);
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* As of this moment, the current CPU has its own GDT pointing
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* to its own TSS. We just need to load the TR register.
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tr_load(gdtselector(TSS_DES));