i386/linux-2.3.21/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__
  44 struct desc_struct {
  45         unsigned long a,b;
  46 };
  47
  48 extern struct desc_struct gdt_table[];
  49 extern struct desc_struct *idt, *gdt;
  50
  51 struct 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  */
  67 extern struct desc_struct default_ldt[];
  68 extern void set_intr_gate(unsigned int irq, void * addr);
  69 extern void set_ldt_desc(unsigned int n, void *addr, unsigned int size);
  70 extern void set_tss_desc(unsigned int n, void *addr);
  71
  72 extern 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  */
  82 extern inline void load_LDT (struct mm_struct *mm)
  83 {
  84         int cpu = smp_processor_id();
  85         void *segments = mm->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