linux/include/asm-x86/desc_32.h

#ifndef __ARCH_DESC_H
#define __ARCH_DESC_H

#include <asm/ldt.h>
#include <asm/segment.h>
#include <asm/desc_defs.h>

#ifndef __ASSEMBLY__

#include <linux/preempt.h>
#include <linux/smp.h>
#include <linux/percpu.h>

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;
}

extern void set_intr_gate(unsigned int irq, void * addr);

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_gate(gate_desc *gate,
	unsigned long base, unsigned short seg, unsigned char type, unsigned char flags)
{
	gate->a = (seg << 16) | (base & 0xffff);
	gate->b = (base & 0xffff0000) | ((type & 0xff) << 8) | (flags & 0xff);
}

#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_ldt_entry(struct desc_struct *ldt, int entry,
					  const void *desc)
{
	memcpy(&ldt[entry], desc, sizeof(struct desc_struct));
}

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_gdt_entry(struct desc_struct *gdt, int entry,
					  const void *desc, int type)
{
	memcpy(&gdt[entry], desc, sizeof(struct desc_struct));
}

static inline void write_dt_entry(struct desc_struct *dt,
				  int entry, u32 entry_low, u32 entry_high)
{
	dt[entry].a = entry_low;
	dt[entry].b = entry_high;
}


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_descriptor(&ldt, (unsigned long)addr,
				entries * sizeof(struct desc_struct) - 1,
				DESC_LDT, 0);
		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 ("sgdt %0":"=m" (*dtr));
}

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

static inline unsigned long native_store_tr(void)
{
	unsigned long tr;
	asm ("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];
}

static inline void _set_gate(int gate, unsigned int type, void *addr, unsigned short seg)
{
	gate_desc g;
	pack_gate(&g, (unsigned long)addr, seg, type, 0);
	write_idt_entry(idt_table, gate, &g);
}

static inline void __set_tss_desc(unsigned int cpu, unsigned int entry, const void *addr)
{
	tss_desc tss;
	pack_descriptor(&tss, (unsigned long)addr,
			offsetof(struct tss_struct, __cacheline_filler) - 1,
			DESC_TSS, 0);
	write_gdt_entry(get_cpu_gdt_table(cpu), entry, &tss, DESC_TSS);
}


#define set_tss_desc(cpu,addr) __set_tss_desc(cpu, GDT_ENTRY_TSS, addr)

static inline unsigned long get_desc_base(unsigned long *desc)
{
	unsigned long base;
	base = ((desc[0] >> 16)  & 0x0000ffff) |
		((desc[1] << 16) & 0x00ff0000) |
		(desc[1] & 0xff000000);
	return base;
}
#endif /* !__ASSEMBLY__ */

#endif