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#ifndef __ARCH_DESC_H

#define __ARCH_DESC_H

#include <asm/ldt.h>

/*

 * The layout of the GDT under Linux:

 *

 *   0 - null

 *   1 - not used

 *   2 - kernel code segment

 *   3 - kernel data segment

 *   4 - user code segment                  <-- new cacheline

 *   5 - user data segment

 *   6 - not used

 *   7 - not used

 *   8 - APM BIOS support                   <-- new cacheline

 *   9 - APM BIOS support

 *  10 - APM BIOS support

 *  11 - APM BIOS support

 *

 * The TSS+LDT descriptors are spread out a bit so that every CPU

 * has an exclusive cacheline for the per-CPU TSS and LDT:

 *

 *  12 - CPU#0 TSS                          <-- new cacheline

 *  13 - CPU#0 LDT

 *  14 - not used

 *  15 - not used

 *  16 - CPU#1 TSS                          <-- new cacheline

 *  17 - CPU#1 LDT

 *  18 - not used

 *  19 - not used

 *  ... NR_CPUS per-CPU TSS+LDT's if on SMP

 *

 * Entry into gdt where to find first TSS.

 */

#define __FIRST_TSS_ENTRY 12

#define __FIRST_LDT_ENTRY (__FIRST_TSS_ENTRY+1)

#define __TSS(n) (((n)<<2) + __FIRST_TSS_ENTRY)

#define __LDT(n) (((n)<<2) + __FIRST_LDT_ENTRY)

#ifndef __ASSEMBLY__

struct desc_struct {

        unsigned long a,b;

};

extern struct desc_struct gdt_table[];

extern struct desc_struct *idt, *gdt;

struct Xgt_desc_struct {

        unsigned short size;

        unsigned long address __attribute__((packed));

};

#define idt_descr (*(struct Xgt_desc_struct *)((char *)&idt - 2))

#define gdt_descr (*(struct Xgt_desc_struct *)((char *)&gdt - 2))

#define load_TR(n) __asm__ __volatile__("ltr %%ax"::"a" (__TSS(n)<<3))

#define __load_LDT(n) __asm__ __volatile__("lldt %%ax"::"a" (__LDT(n)<<3))

/*

 * This is the ldt that every process will get unless we need

 * something other than this.

 */

extern struct desc_struct default_ldt[];

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

extern void set_ldt_desc(unsigned int n, void *addr, unsigned int size);

extern void set_tss_desc(unsigned int n, void *addr);

static inline void clear_LDT(void)

{

        int cpu = smp_processor_id();

        set_ldt_desc(cpu, &default_ldt[0], 5);

        __load_LDT(cpu);

}

/*

 * load one particular LDT into the current CPU

 */

static inline void load_LDT (mm_context_t *pc)

{

        int cpu = smp_processor_id();

        void *segments = pc->ldt;

        int count = pc->size;

        if (!count) {

                segments = &default_ldt[0];

                count = 5;

        }

        set_ldt_desc(cpu, segments, count);

        __load_LDT(cpu);

}

#endif /* !__ASSEMBLY__ */

#endif