LXR linux-old/include/asm-i386/desc.h

   1#ifndef __ARCH_DESC_H
   2#define __ARCH_DESC_H
   3
   4#include <asm/ldt.h>
   5
   6/*
   7 * The layout of the GDT under Linux:
   8 *
   9 *   0 - null
  10 *   1 - not used
  11 *   2 - kernel code segment
  12 *   3 - kernel data segment
  13 *   4 - user code segment                  <-- new cacheline 
  14 *   5 - user data segment
  15 *   6 - not used
  16 *   7 - not used
  17 *   8 - APM BIOS support                   <-- new cacheline 
  18 *   9 - APM BIOS support
  19 *  10 - APM BIOS support
  20 *  11 - APM BIOS support
  21 *
  22 * The TSS+LDT descriptors are spread out a bit so that every CPU
  23 * has an exclusive cacheline for the per-CPU TSS and LDT:
  24 *
  25 *  12 - CPU#0 TSS                          <-- new cacheline 
  26 *  13 - CPU#0 LDT
  27 *  14 - not used 
  28 *  15 - not used 
  29 *  16 - CPU#1 TSS                          <-- new cacheline 
  30 *  17 - CPU#1 LDT
  31 *  18 - not used 
  32 *  19 - not used 
  33 *  ... NR_CPUS per-CPU TSS+LDT's if on SMP
  34 *
  35 * Entry into gdt where to find first TSS.
  36 */
  37#define __FIRST_TSS_ENTRY 12
  38#define __FIRST_LDT_ENTRY (__FIRST_TSS_ENTRY+1)
  39
  40#define __TSS(n) (((n)<<2) + __FIRST_TSS_ENTRY)
  41#define __LDT(n) (((n)<<2) + __FIRST_LDT_ENTRY)
  42
  43#ifndef __ASSEMBLY__
  44struct desc_struct {
  45        unsigned long a,b;
  46};
  47
  48extern struct desc_struct gdt_table[];
  49extern struct desc_struct *idt, *gdt;
  50
  51struct Xgt_desc_struct {
  52        unsigned short size;
  53        unsigned long address __attribute__((packed));
  54};
  55
  56#define idt_descr (*(struct Xgt_desc_struct *)((char *)&idt - 2))
  57#define gdt_descr (*(struct Xgt_desc_struct *)((char *)&gdt - 2))
  58
  59#define load_TR(n) __asm__ __volatile__("ltr %%ax"::"a" (__TSS(n)<<3))
  60
  61#define __load_LDT(n) __asm__ __volatile__("lldt %%ax"::"a" (__LDT(n)<<3))
  62
  63/*
  64 * This is the ldt that every process will get unless we need
  65 * something other than this.
  66 */
  67extern struct desc_struct default_ldt[];
  68extern void set_intr_gate(unsigned int irq, void * addr);
  69extern void set_ldt_desc(unsigned int n, void *addr, unsigned int size);
  70extern void set_tss_desc(unsigned int n, void *addr);
  71
  72static inline void clear_LDT(void)
  73{
  74        int cpu = smp_processor_id();
  75        set_ldt_desc(cpu, &default_ldt[0], 5);
  76        __load_LDT(cpu);
  77}
  78
  79/*
  80 * load one particular LDT into the current CPU
  81 */
  82static inline void load_LDT (struct mm_struct *mm)
  83{
  84        int cpu = smp_processor_id();
  85        void *segments = mm->context.segments;
  86        int count = LDT_ENTRIES;
  87
  88        if (!segments) {
  89                segments = &default_ldt[0];
  90                count = 5;
  91        }
  92                
  93        set_ldt_desc(cpu, segments, count);
  94        __load_LDT(cpu);
  95}
  96
  97#endif /* !__ASSEMBLY__ */
  98
  99#endif
 100