linux/include/asm-x86/desc.h

#ifndef _ASM_DESC_H_
#define _ASM_DESC_H_

#ifndef __ASSEMBLY__
#include <asm/desc_defs.h>
#include <asm/ldt.h>
#include <asm/mmu.h>
#include <linux/smp.h>

static inline void fill_ldt(struct desc_struct *desc, struct user_desc *info)
{
	desc->limit0 = info->limit & 0x0ffff;
	desc->base0 = info->base_addr & 0x0000ffff;

	desc->base1 = (info->base_addr & 0x00ff0000) >> 16;
	desc->type = (info->read_exec_only ^ 1) << 1;
	desc->type |= info->contents << 2;
	desc->s = 1;
	desc->dpl = 0x3;
	desc->p = info->seg_not_present ^ 1;
	desc->limit = (info->limit & 0xf0000) >> 16;
	desc->avl = info->useable;
	desc->d = info->seg_32bit;
	desc->g = info->limit_in_pages;
	desc->base2 = (info->base_addr & 0xff000000) >> 24;
}

extern struct desc_ptr idt_descr;
extern gate_desc idt_table[];

#ifdef CONFIG_X86_64
extern struct desc_struct cpu_gdt_table[GDT_ENTRIES];
extern struct desc_ptr cpu_gdt_descr[];
/* the cpu gdt accessor */
#define get_cpu_gdt_table(x) ((struct desc_struct *)cpu_gdt_descr[x].address)
#else
struct gdt_page {
	struct desc_struct gdt[GDT_ENTRIES];
} __attribute__((aligned(PAGE_SIZE)));
DECLARE_PER_CPU(struct gdt_page, gdt_page);

static inline struct desc_struct *get_cpu_gdt_table(unsigned int cpu)
{
	return per_cpu(gdt_page, cpu).gdt;
}
#endif

#ifdef CONFIG_PARAVIRT
#include <asm/paravirt.h>
#else
#define load_TR_desc() native_load_tr_desc()
#define load_gdt(dtr) native_load_gdt(dtr)
#define load_idt(dtr) native_load_idt(dtr)
#define load_tr(tr) __asm__ __volatile("ltr %0"::"m" (tr))
#define load_ldt(ldt) __asm__ __volatile("lldt %0"::"m" (ldt))

#define store_gdt(dtr) native_store_gdt(dtr)
#define store_idt(dtr) native_store_idt(dtr)
#define store_tr(tr) (tr = native_store_tr())
#define store_ldt(ldt) __asm__ ("sldt %0":"=m" (ldt))

#define load_TLS(t, cpu) native_load_tls(t, cpu)
#define set_ldt native_set_ldt

#define write_ldt_entry(dt, entry, desc) \
				native_write_ldt_entry(dt, entry, desc)
#define write_gdt_entry(dt, entry, desc, type) \
				native_write_gdt_entry(dt, entry, desc, type)
#define write_idt_entry(dt, entry, g) native_write_idt_entry(dt, entry, g)
#endif

static inline void native_write_idt_entry(gate_desc *idt, int entry,
					  const gate_desc *gate)
{
	memcpy(&idt[entry], gate, sizeof(*gate));
}

static inline void native_write_ldt_entry(struct desc_struct *ldt, int entry,
					  const void *desc)
{
	memcpy(&ldt[entry], desc, 8);
}

static inline void native_write_gdt_entry(struct desc_struct *gdt, int entry,
					  const void *desc, int type)
{
	unsigned int size;
	switch (type) {
	case DESC_TSS:
		size = sizeof(tss_desc);
		break;
	case DESC_LDT:
		size = sizeof(ldt_desc);
		break;
	default:
		size = sizeof(struct desc_struct);
		break;
	}
	memcpy(&gdt[entry], desc, size);
}

static inline void set_tssldt_descriptor(struct ldttss_desc64 *d,
					 unsigned long tss, unsigned type,
					 unsigned size)
{
	memset(d, 0, sizeof(*d));
	d->limit0 = size & 0xFFFF;
	d->base0 = PTR_LOW(tss);
	d->base1 = PTR_MIDDLE(tss) & 0xFF;
	d->type = type;
	d->p = 1;
	d->limit1 = (size >> 16) & 0xF;
	d->base2 = (PTR_MIDDLE(tss) >> 8) & 0xFF;
	d->base3 = PTR_HIGH(tss);
}

static inline void pack_descriptor(struct desc_struct *desc, unsigned long base,
				   unsigned long limit, unsigned char type,
				   unsigned char flags)
{
	desc->a = ((base & 0xffff) << 16) | (limit & 0xffff);
	desc->b = (base & 0xff000000) | ((base & 0xff0000) >> 16) |
		  (limit & 0x000f0000) | ((type & 0xff) << 8) |
		  ((flags & 0xf) << 20);
	desc->p = 1;
}

static inline void pack_ldt(ldt_desc *ldt, unsigned long addr,
			   unsigned size)
{

#ifdef CONFIG_X86_64
		set_tssldt_descriptor(ldt,
			     addr, DESC_LDT, size);
#else
		pack_descriptor(ldt, (unsigned long)addr,
				size,
				0x80 | DESC_LDT, 0);
#endif
}

static inline void native_set_ldt(const void *addr, unsigned int entries)
{
	if (likely(entries == 0))
		__asm__ __volatile__("lldt %w0"::"q" (0));
	else {
		unsigned cpu = smp_processor_id();
		ldt_desc ldt;

		pack_ldt(&ldt, (unsigned long)addr,
				entries * sizeof(ldt) - 1);
		write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_LDT,
				&ldt, DESC_LDT);
		__asm__ __volatile__("lldt %w0"::"q" (GDT_ENTRY_LDT*8));
	}
}

static inline void native_load_tr_desc(void)
{
	asm volatile("ltr %w0"::"q" (GDT_ENTRY_TSS*8));
}

static inline void native_load_gdt(const struct desc_ptr *dtr)
{
	asm volatile("lgdt %0"::"m" (*dtr));
}

static inline void native_load_idt(const struct desc_ptr *dtr)
{
	asm volatile("lidt %0"::"m" (*dtr));
}

static inline void native_store_gdt(struct desc_ptr *dtr)
{
	asm volatile("sgdt %0":"=m" (*dtr));
}

static inline void native_store_idt(struct desc_ptr *dtr)
{
	asm volatile("sidt %0":"=m" (*dtr));
}

static inline unsigned long native_store_tr(void)
{
	unsigned long tr;
	asm volatile("str %0":"=r" (tr));
	return tr;
}

static inline void native_load_tls(struct thread_struct *t, unsigned int cpu)
{
	unsigned int i;
	struct desc_struct *gdt = get_cpu_gdt_table(cpu);

	for (i = 0; i < GDT_ENTRY_TLS_ENTRIES; i++)
		gdt[GDT_ENTRY_TLS_MIN + i] = t->tls_array[i];
}

#ifdef CONFIG_X86_32
# include "desc_32.h"
#else
# include "desc_64.h"
#endif

#define _LDT_empty(info) (\
	(info)->base_addr	== 0	&& \
	(info)->limit		== 0	&& \
	(info)->contents	== 0	&& \
	(info)->read_exec_only	== 1	&& \
	(info)->seg_32bit	== 0	&& \
	(info)->limit_in_pages	== 0	&& \
	(info)->seg_not_present	== 1	&& \
	(info)->useable		== 0)

#ifdef CONFIG_X86_64
#define LDT_empty(info) (_LDT_empty(info) && ((info)->lm == 0))
#else
#define LDT_empty(info) (_LDT_empty(info))
#endif

static inline void clear_LDT(void)
{
	set_ldt(NULL, 0);
}

/*
 * load one particular LDT into the current CPU
 */
static inline void load_LDT_nolock(mm_context_t *pc)
{
	set_ldt(pc->ldt, pc->size);
}

static inline void load_LDT(mm_context_t *pc)
{
	preempt_disable();
	load_LDT_nolock(pc);
	preempt_enable();
}

static inline unsigned long get_desc_base(struct desc_struct *desc)
{
	return desc->base0 | ((desc->base1) << 16) | ((desc->base2) << 24);
}

#else
/*
 * GET_DESC_BASE reads the descriptor base of the specified segment.
 *
 * Args:
 *    idx - descriptor index
 *    gdt - GDT pointer
 *    base - 32bit register to which the base will be written
 *    lo_w - lo word of the "base" register
 *    lo_b - lo byte of the "base" register
 *    hi_b - hi byte of the low word of the "base" register
 *
 * Example:
 *    GET_DESC_BASE(GDT_ENTRY_ESPFIX_SS, %ebx, %eax, %ax, %al, %ah)
 *    Will read the base address of GDT_ENTRY_ESPFIX_SS and put it into %eax.
 */
#define GET_DESC_BASE(idx, gdt, base, lo_w, lo_b, hi_b) \
	movb idx*8+4(gdt), lo_b; \
	movb idx*8+7(gdt), hi_b; \
	shll $16, base; \
	movw idx*8+2(gdt), lo_w;


#endif /* __ASSEMBLY__ */

#endif