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->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
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