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segment.h
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1 #ifndef _ASM_X86_SEGMENT_H
2 #define _ASM_X86_SEGMENT_H
3 
4 #include <linux/const.h>
5 
6 /* Constructor for a conventional segment GDT (or LDT) entry */
7 /* This is a macro so it can be used in initializers */
8 #define GDT_ENTRY(flags, base, limit) \
9  ((((base) & _AC(0xff000000,ULL)) << (56-24)) | \
10  (((flags) & _AC(0x0000f0ff,ULL)) << 40) | \
11  (((limit) & _AC(0x000f0000,ULL)) << (48-16)) | \
12  (((base) & _AC(0x00ffffff,ULL)) << 16) | \
13  (((limit) & _AC(0x0000ffff,ULL))))
14 
15 /* Simple and small GDT entries for booting only */
16 
17 #define GDT_ENTRY_BOOT_CS 2
18 #define __BOOT_CS (GDT_ENTRY_BOOT_CS * 8)
19 
20 #define GDT_ENTRY_BOOT_DS (GDT_ENTRY_BOOT_CS + 1)
21 #define __BOOT_DS (GDT_ENTRY_BOOT_DS * 8)
22 
23 #define GDT_ENTRY_BOOT_TSS (GDT_ENTRY_BOOT_CS + 2)
24 #define __BOOT_TSS (GDT_ENTRY_BOOT_TSS * 8)
25 
26 #ifdef CONFIG_X86_32
27 /*
28  * The layout of the per-CPU GDT under Linux:
29  *
30  * 0 - null
31  * 1 - reserved
32  * 2 - reserved
33  * 3 - reserved
34  *
35  * 4 - unused <==== new cacheline
36  * 5 - unused
37  *
38  * ------- start of TLS (Thread-Local Storage) segments:
39  *
40  * 6 - TLS segment #1 [ glibc's TLS segment ]
41  * 7 - TLS segment #2 [ Wine's %fs Win32 segment ]
42  * 8 - TLS segment #3
43  * 9 - reserved
44  * 10 - reserved
45  * 11 - reserved
46  *
47  * ------- start of kernel segments:
48  *
49  * 12 - kernel code segment <==== new cacheline
50  * 13 - kernel data segment
51  * 14 - default user CS
52  * 15 - default user DS
53  * 16 - TSS
54  * 17 - LDT
55  * 18 - PNPBIOS support (16->32 gate)
56  * 19 - PNPBIOS support
57  * 20 - PNPBIOS support
58  * 21 - PNPBIOS support
59  * 22 - PNPBIOS support
60  * 23 - APM BIOS support
61  * 24 - APM BIOS support
62  * 25 - APM BIOS support
63  *
64  * 26 - ESPFIX small SS
65  * 27 - per-cpu [ offset to per-cpu data area ]
66  * 28 - stack_canary-20 [ for stack protector ]
67  * 29 - unused
68  * 30 - unused
69  * 31 - TSS for double fault handler
70  */
71 #define GDT_ENTRY_TLS_MIN 6
72 #define GDT_ENTRY_TLS_MAX (GDT_ENTRY_TLS_MIN + GDT_ENTRY_TLS_ENTRIES - 1)
73 
74 #define GDT_ENTRY_DEFAULT_USER_CS 14
75 
76 #define GDT_ENTRY_DEFAULT_USER_DS 15
77 
78 #define GDT_ENTRY_KERNEL_BASE (12)
79 
80 #define GDT_ENTRY_KERNEL_CS (GDT_ENTRY_KERNEL_BASE+0)
81 
82 #define GDT_ENTRY_KERNEL_DS (GDT_ENTRY_KERNEL_BASE+1)
83 
84 #define GDT_ENTRY_TSS (GDT_ENTRY_KERNEL_BASE+4)
85 #define GDT_ENTRY_LDT (GDT_ENTRY_KERNEL_BASE+5)
86 
87 #define GDT_ENTRY_PNPBIOS_BASE (GDT_ENTRY_KERNEL_BASE+6)
88 #define GDT_ENTRY_APMBIOS_BASE (GDT_ENTRY_KERNEL_BASE+11)
89 
90 #define GDT_ENTRY_ESPFIX_SS (GDT_ENTRY_KERNEL_BASE+14)
91 #define __ESPFIX_SS (GDT_ENTRY_ESPFIX_SS*8)
92 
93 #define GDT_ENTRY_PERCPU (GDT_ENTRY_KERNEL_BASE+15)
94 #ifdef CONFIG_SMP
95 #define __KERNEL_PERCPU (GDT_ENTRY_PERCPU * 8)
96 #else
97 #define __KERNEL_PERCPU 0
98 #endif
99 
100 #define GDT_ENTRY_STACK_CANARY (GDT_ENTRY_KERNEL_BASE+16)
101 #ifdef CONFIG_CC_STACKPROTECTOR
102 #define __KERNEL_STACK_CANARY (GDT_ENTRY_STACK_CANARY*8)
103 #else
104 #define __KERNEL_STACK_CANARY 0
105 #endif
106 
107 #define GDT_ENTRY_DOUBLEFAULT_TSS 31
108 
109 /*
110  * The GDT has 32 entries
111  */
112 #define GDT_ENTRIES 32
113 
114 /* The PnP BIOS entries in the GDT */
115 #define GDT_ENTRY_PNPBIOS_CS32 (GDT_ENTRY_PNPBIOS_BASE + 0)
116 #define GDT_ENTRY_PNPBIOS_CS16 (GDT_ENTRY_PNPBIOS_BASE + 1)
117 #define GDT_ENTRY_PNPBIOS_DS (GDT_ENTRY_PNPBIOS_BASE + 2)
118 #define GDT_ENTRY_PNPBIOS_TS1 (GDT_ENTRY_PNPBIOS_BASE + 3)
119 #define GDT_ENTRY_PNPBIOS_TS2 (GDT_ENTRY_PNPBIOS_BASE + 4)
120 
121 /* The PnP BIOS selectors */
122 #define PNP_CS32 (GDT_ENTRY_PNPBIOS_CS32 * 8) /* segment for calling fn */
123 #define PNP_CS16 (GDT_ENTRY_PNPBIOS_CS16 * 8) /* code segment for BIOS */
124 #define PNP_DS (GDT_ENTRY_PNPBIOS_DS * 8) /* data segment for BIOS */
125 #define PNP_TS1 (GDT_ENTRY_PNPBIOS_TS1 * 8) /* transfer data segment */
126 #define PNP_TS2 (GDT_ENTRY_PNPBIOS_TS2 * 8) /* another data segment */
127 
128 /* Bottom two bits of selector give the ring privilege level */
129 #define SEGMENT_RPL_MASK 0x3
130 /* Bit 2 is table indicator (LDT/GDT) */
131 #define SEGMENT_TI_MASK 0x4
132 
133 /* User mode is privilege level 3 */
134 #define USER_RPL 0x3
135 /* LDT segment has TI set, GDT has it cleared */
136 #define SEGMENT_LDT 0x4
137 #define SEGMENT_GDT 0x0
138 
139 /*
140  * Matching rules for certain types of segments.
141  */
142 
143 /* Matches PNP_CS32 and PNP_CS16 (they must be consecutive) */
144 #define SEGMENT_IS_PNP_CODE(x) (((x) & 0xf4) == GDT_ENTRY_PNPBIOS_BASE * 8)
145 
146 
147 #else
148 #include <asm/cache.h>
149 
150 #define GDT_ENTRY_KERNEL32_CS 1
151 #define GDT_ENTRY_KERNEL_CS 2
152 #define GDT_ENTRY_KERNEL_DS 3
153 
154 #define __KERNEL32_CS (GDT_ENTRY_KERNEL32_CS * 8)
155 
156 /*
157  * we cannot use the same code segment descriptor for user and kernel
158  * -- not even in the long flat mode, because of different DPL /kkeil
159  * The segment offset needs to contain a RPL. Grr. -AK
160  * GDT layout to get 64bit syscall right (sysret hardcodes gdt offsets)
161  */
162 #define GDT_ENTRY_DEFAULT_USER32_CS 4
163 #define GDT_ENTRY_DEFAULT_USER_DS 5
164 #define GDT_ENTRY_DEFAULT_USER_CS 6
165 #define __USER32_CS (GDT_ENTRY_DEFAULT_USER32_CS*8+3)
166 #define __USER32_DS __USER_DS
167 
168 #define GDT_ENTRY_TSS 8 /* needs two entries */
169 #define GDT_ENTRY_LDT 10 /* needs two entries */
170 #define GDT_ENTRY_TLS_MIN 12
171 #define GDT_ENTRY_TLS_MAX 14
172 
173 #define GDT_ENTRY_PER_CPU 15 /* Abused to load per CPU data from limit */
174 #define __PER_CPU_SEG (GDT_ENTRY_PER_CPU * 8 + 3)
175 
176 /* TLS indexes for 64bit - hardcoded in arch_prctl */
177 #define FS_TLS 0
178 #define GS_TLS 1
179 
180 #define GS_TLS_SEL ((GDT_ENTRY_TLS_MIN+GS_TLS)*8 + 3)
181 #define FS_TLS_SEL ((GDT_ENTRY_TLS_MIN+FS_TLS)*8 + 3)
182 
183 #define GDT_ENTRIES 16
184 
185 #endif
186 
187 #define __KERNEL_CS (GDT_ENTRY_KERNEL_CS*8)
188 #define __KERNEL_DS (GDT_ENTRY_KERNEL_DS*8)
189 #define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS*8+3)
190 #define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8+3)
191 #ifndef CONFIG_PARAVIRT
192 #define get_kernel_rpl() 0
193 #endif
194 
195 /* User mode is privilege level 3 */
196 #define USER_RPL 0x3
197 /* LDT segment has TI set, GDT has it cleared */
198 #define SEGMENT_LDT 0x4
199 #define SEGMENT_GDT 0x0
200 
201 /* Bottom two bits of selector give the ring privilege level */
202 #define SEGMENT_RPL_MASK 0x3
203 /* Bit 2 is table indicator (LDT/GDT) */
204 #define SEGMENT_TI_MASK 0x4
205 
206 #define IDT_ENTRIES 256
207 #define NUM_EXCEPTION_VECTORS 32
208 /* Bitmask of exception vectors which push an error code on the stack */
209 #define EXCEPTION_ERRCODE_MASK 0x00027d00
210 #define GDT_SIZE (GDT_ENTRIES * 8)
211 #define GDT_ENTRY_TLS_ENTRIES 3
212 #define TLS_SIZE (GDT_ENTRY_TLS_ENTRIES * 8)
213 
214 #ifdef __KERNEL__
215 #ifndef __ASSEMBLY__
216 extern const char early_idt_handlers[NUM_EXCEPTION_VECTORS][2+2+5];
217 
218 /*
219  * Load a segment. Fall back on loading the zero
220  * segment if something goes wrong..
221  */
222 #define loadsegment(seg, value) \
223 do { \
224  unsigned short __val = (value); \
225  \
226  asm volatile(" \n" \
227  "1: movl %k0,%%" #seg " \n" \
228  \
229  ".section .fixup,\"ax\" \n" \
230  "2: xorl %k0,%k0 \n" \
231  " jmp 1b \n" \
232  ".previous \n" \
233  \
234  _ASM_EXTABLE(1b, 2b) \
235  \
236  : "+r" (__val) : : "memory"); \
237 } while (0)
238 
239 /*
240  * Save a segment register away
241  */
242 #define savesegment(seg, value) \
243  asm("mov %%" #seg ",%0":"=r" (value) : : "memory")
244 
245 /*
246  * x86_32 user gs accessors.
247  */
248 #ifdef CONFIG_X86_32
249 #ifdef CONFIG_X86_32_LAZY_GS
250 #define get_user_gs(regs) (u16)({unsigned long v; savesegment(gs, v); v;})
251 #define set_user_gs(regs, v) loadsegment(gs, (unsigned long)(v))
252 #define task_user_gs(tsk) ((tsk)->thread.gs)
253 #define lazy_save_gs(v) savesegment(gs, (v))
254 #define lazy_load_gs(v) loadsegment(gs, (v))
255 #else /* X86_32_LAZY_GS */
256 #define get_user_gs(regs) (u16)((regs)->gs)
257 #define set_user_gs(regs, v) do { (regs)->gs = (v); } while (0)
258 #define task_user_gs(tsk) (task_pt_regs(tsk)->gs)
259 #define lazy_save_gs(v) do { } while (0)
260 #define lazy_load_gs(v) do { } while (0)
261 #endif /* X86_32_LAZY_GS */
262 #endif /* X86_32 */
263 
264 static inline unsigned long get_limit(unsigned long segment)
265 {
266  unsigned long __limit;
267  asm("lsll %1,%0" : "=r" (__limit) : "r" (segment));
268  return __limit + 1;
269 }
270 
271 #endif /* !__ASSEMBLY__ */
272 #endif /* __KERNEL__ */
273 
274 #endif /* _ASM_X86_SEGMENT_H */
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