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Linux/arch/x86/include/asm/segment.h

  1 #ifndef _ASM_X86_SEGMENT_H
  2 #define _ASM_X86_SEGMENT_H
  3 
  4 #include <linux/const.h>
  5 #include <asm/alternative.h>
  6 
  7 /*
  8  * Constructor for a conventional segment GDT (or LDT) entry.
  9  * This is a macro so it can be used in initializers.
 10  */
 11 #define GDT_ENTRY(flags, base, limit)                   \
 12         ((((base)  & _AC(0xff000000,ULL)) << (56-24)) | \
 13          (((flags) & _AC(0x0000f0ff,ULL)) << 40) |      \
 14          (((limit) & _AC(0x000f0000,ULL)) << (48-16)) | \
 15          (((base)  & _AC(0x00ffffff,ULL)) << 16) |      \
 16          (((limit) & _AC(0x0000ffff,ULL))))
 17 
 18 /* Simple and small GDT entries for booting only: */
 19 
 20 #define GDT_ENTRY_BOOT_CS       2
 21 #define GDT_ENTRY_BOOT_DS       3
 22 #define GDT_ENTRY_BOOT_TSS      4
 23 #define __BOOT_CS               (GDT_ENTRY_BOOT_CS*8)
 24 #define __BOOT_DS               (GDT_ENTRY_BOOT_DS*8)
 25 #define __BOOT_TSS              (GDT_ENTRY_BOOT_TSS*8)
 26 
 27 /*
 28  * Bottom two bits of selector give the ring
 29  * privilege level
 30  */
 31 #define SEGMENT_RPL_MASK        0x3
 32 
 33 /* User mode is privilege level 3: */
 34 #define USER_RPL                0x3
 35 
 36 /* Bit 2 is Table Indicator (TI): selects between LDT or GDT */
 37 #define SEGMENT_TI_MASK         0x4
 38 /* LDT segment has TI set ... */
 39 #define SEGMENT_LDT             0x4
 40 /* ... GDT has it cleared */
 41 #define SEGMENT_GDT             0x0
 42 
 43 #define GDT_ENTRY_INVALID_SEG   0
 44 
 45 #ifdef CONFIG_X86_32
 46 /*
 47  * The layout of the per-CPU GDT under Linux:
 48  *
 49  *   0 - null                                                           <=== cacheline #1
 50  *   1 - reserved
 51  *   2 - reserved
 52  *   3 - reserved
 53  *
 54  *   4 - unused                                                         <=== cacheline #2
 55  *   5 - unused
 56  *
 57  *  ------- start of TLS (Thread-Local Storage) segments:
 58  *
 59  *   6 - TLS segment #1                 [ glibc's TLS segment ]
 60  *   7 - TLS segment #2                 [ Wine's %fs Win32 segment ]
 61  *   8 - TLS segment #3                                                 <=== cacheline #3
 62  *   9 - reserved
 63  *  10 - reserved
 64  *  11 - reserved
 65  *
 66  *  ------- start of kernel segments:
 67  *
 68  *  12 - kernel code segment                                            <=== cacheline #4
 69  *  13 - kernel data segment
 70  *  14 - default user CS
 71  *  15 - default user DS
 72  *  16 - TSS                                                            <=== cacheline #5
 73  *  17 - LDT
 74  *  18 - PNPBIOS support (16->32 gate)
 75  *  19 - PNPBIOS support
 76  *  20 - PNPBIOS support                                                <=== cacheline #6
 77  *  21 - PNPBIOS support
 78  *  22 - PNPBIOS support
 79  *  23 - APM BIOS support
 80  *  24 - APM BIOS support                                               <=== cacheline #7
 81  *  25 - APM BIOS support
 82  *
 83  *  26 - ESPFIX small SS
 84  *  27 - per-cpu                        [ offset to per-cpu data area ]
 85  *  28 - stack_canary-20                [ for stack protector ]         <=== cacheline #8
 86  *  29 - unused
 87  *  30 - unused
 88  *  31 - TSS for double fault handler
 89  */
 90 #define GDT_ENTRY_TLS_MIN               6
 91 #define GDT_ENTRY_TLS_MAX               (GDT_ENTRY_TLS_MIN + GDT_ENTRY_TLS_ENTRIES - 1)
 92 
 93 #define GDT_ENTRY_KERNEL_CS             12
 94 #define GDT_ENTRY_KERNEL_DS             13
 95 #define GDT_ENTRY_DEFAULT_USER_CS       14
 96 #define GDT_ENTRY_DEFAULT_USER_DS       15
 97 #define GDT_ENTRY_TSS                   16
 98 #define GDT_ENTRY_LDT                   17
 99 #define GDT_ENTRY_PNPBIOS_CS32          18
100 #define GDT_ENTRY_PNPBIOS_CS16          19
101 #define GDT_ENTRY_PNPBIOS_DS            20
102 #define GDT_ENTRY_PNPBIOS_TS1           21
103 #define GDT_ENTRY_PNPBIOS_TS2           22
104 #define GDT_ENTRY_APMBIOS_BASE          23
105 
106 #define GDT_ENTRY_ESPFIX_SS             26
107 #define GDT_ENTRY_PERCPU                27
108 #define GDT_ENTRY_STACK_CANARY          28
109 
110 #define GDT_ENTRY_DOUBLEFAULT_TSS       31
111 
112 /*
113  * Number of entries in the GDT table:
114  */
115 #define GDT_ENTRIES                     32
116 
117 /*
118  * Segment selector values corresponding to the above entries:
119  */
120 
121 #define __KERNEL_CS                     (GDT_ENTRY_KERNEL_CS*8)
122 #define __KERNEL_DS                     (GDT_ENTRY_KERNEL_DS*8)
123 #define __USER_DS                       (GDT_ENTRY_DEFAULT_USER_DS*8 + 3)
124 #define __USER_CS                       (GDT_ENTRY_DEFAULT_USER_CS*8 + 3)
125 #define __ESPFIX_SS                     (GDT_ENTRY_ESPFIX_SS*8)
126 
127 /* segment for calling fn: */
128 #define PNP_CS32                        (GDT_ENTRY_PNPBIOS_CS32*8)
129 /* code segment for BIOS: */
130 #define PNP_CS16                        (GDT_ENTRY_PNPBIOS_CS16*8)
131 
132 /* "Is this PNP code selector (PNP_CS32 or PNP_CS16)?" */
133 #define SEGMENT_IS_PNP_CODE(x)          (((x) & 0xf4) == PNP_CS32)
134 
135 /* data segment for BIOS: */
136 #define PNP_DS                          (GDT_ENTRY_PNPBIOS_DS*8)
137 /* transfer data segment: */
138 #define PNP_TS1                         (GDT_ENTRY_PNPBIOS_TS1*8)
139 /* another data segment: */
140 #define PNP_TS2                         (GDT_ENTRY_PNPBIOS_TS2*8)
141 
142 #ifdef CONFIG_SMP
143 # define __KERNEL_PERCPU                (GDT_ENTRY_PERCPU*8)
144 #else
145 # define __KERNEL_PERCPU                0
146 #endif
147 
148 #ifdef CONFIG_CC_STACKPROTECTOR
149 # define __KERNEL_STACK_CANARY          (GDT_ENTRY_STACK_CANARY*8)
150 #else
151 # define __KERNEL_STACK_CANARY          0
152 #endif
153 
154 #else /* 64-bit: */
155 
156 #include <asm/cache.h>
157 
158 #define GDT_ENTRY_KERNEL32_CS           1
159 #define GDT_ENTRY_KERNEL_CS             2
160 #define GDT_ENTRY_KERNEL_DS             3
161 
162 /*
163  * We cannot use the same code segment descriptor for user and kernel mode,
164  * not even in long flat mode, because of different DPL.
165  *
166  * GDT layout to get 64-bit SYSCALL/SYSRET support right. SYSRET hardcodes
167  * selectors:
168  *
169  *   if returning to 32-bit userspace: cs = STAR.SYSRET_CS,
170  *   if returning to 64-bit userspace: cs = STAR.SYSRET_CS+16,
171  *
172  * ss = STAR.SYSRET_CS+8 (in either case)
173  *
174  * thus USER_DS should be between 32-bit and 64-bit code selectors:
175  */
176 #define GDT_ENTRY_DEFAULT_USER32_CS     4
177 #define GDT_ENTRY_DEFAULT_USER_DS       5
178 #define GDT_ENTRY_DEFAULT_USER_CS       6
179 
180 /* Needs two entries */
181 #define GDT_ENTRY_TSS                   8
182 /* Needs two entries */
183 #define GDT_ENTRY_LDT                   10
184 
185 #define GDT_ENTRY_TLS_MIN               12
186 #define GDT_ENTRY_TLS_MAX               14
187 
188 /* Abused to load per CPU data from limit */
189 #define GDT_ENTRY_PER_CPU               15
190 
191 /*
192  * Number of entries in the GDT table:
193  */
194 #define GDT_ENTRIES                     16
195 
196 /*
197  * Segment selector values corresponding to the above entries:
198  *
199  * Note, selectors also need to have a correct RPL,
200  * expressed with the +3 value for user-space selectors:
201  */
202 #define __KERNEL32_CS                   (GDT_ENTRY_KERNEL32_CS*8)
203 #define __KERNEL_CS                     (GDT_ENTRY_KERNEL_CS*8)
204 #define __KERNEL_DS                     (GDT_ENTRY_KERNEL_DS*8)
205 #define __USER32_CS                     (GDT_ENTRY_DEFAULT_USER32_CS*8 + 3)
206 #define __USER_DS                       (GDT_ENTRY_DEFAULT_USER_DS*8 + 3)
207 #define __USER32_DS                     __USER_DS
208 #define __USER_CS                       (GDT_ENTRY_DEFAULT_USER_CS*8 + 3)
209 #define __PER_CPU_SEG                   (GDT_ENTRY_PER_CPU*8 + 3)
210 
211 #endif
212 
213 #ifndef CONFIG_PARAVIRT
214 # define get_kernel_rpl()               0
215 #endif
216 
217 #define IDT_ENTRIES                     256
218 #define NUM_EXCEPTION_VECTORS           32
219 
220 /* Bitmask of exception vectors which push an error code on the stack: */
221 #define EXCEPTION_ERRCODE_MASK          0x00027d00
222 
223 #define GDT_SIZE                        (GDT_ENTRIES*8)
224 #define GDT_ENTRY_TLS_ENTRIES           3
225 #define TLS_SIZE                        (GDT_ENTRY_TLS_ENTRIES* 8)
226 
227 #ifdef __KERNEL__
228 
229 /*
230  * early_idt_handler_array is an array of entry points referenced in the
231  * early IDT.  For simplicity, it's a real array with one entry point
232  * every nine bytes.  That leaves room for an optional 'push $0' if the
233  * vector has no error code (two bytes), a 'push $vector_number' (two
234  * bytes), and a jump to the common entry code (up to five bytes).
235  */
236 #define EARLY_IDT_HANDLER_SIZE 9
237 
238 #ifndef __ASSEMBLY__
239 
240 extern const char early_idt_handler_array[NUM_EXCEPTION_VECTORS][EARLY_IDT_HANDLER_SIZE];
241 #ifdef CONFIG_TRACING
242 # define trace_early_idt_handler_array early_idt_handler_array
243 #endif
244 
245 /*
246  * Load a segment. Fall back on loading the zero segment if something goes
247  * wrong.  This variant assumes that loading zero fully clears the segment.
248  * This is always the case on Intel CPUs and, even on 64-bit AMD CPUs, any
249  * failure to fully clear the cached descriptor is only observable for
250  * FS and GS.
251  */
252 #define __loadsegment_simple(seg, value)                                \
253 do {                                                                    \
254         unsigned short __val = (value);                                 \
255                                                                         \
256         asm volatile("                                          \n"     \
257                      "1:        movl %k0,%%" #seg "             \n"     \
258                                                                         \
259                      ".section .fixup,\"ax\"                    \n"     \
260                      "2:        xorl %k0,%k0                    \n"     \
261                      "          jmp 1b                          \n"     \
262                      ".previous                                 \n"     \
263                                                                         \
264                      _ASM_EXTABLE(1b, 2b)                               \
265                                                                         \
266                      : "+r" (__val) : : "memory");                      \
267 } while (0)
268 
269 #define __loadsegment_ss(value) __loadsegment_simple(ss, (value))
270 #define __loadsegment_ds(value) __loadsegment_simple(ds, (value))
271 #define __loadsegment_es(value) __loadsegment_simple(es, (value))
272 
273 #ifdef CONFIG_X86_32
274 
275 /*
276  * On 32-bit systems, the hidden parts of FS and GS are unobservable if
277  * the selector is NULL, so there's no funny business here.
278  */
279 #define __loadsegment_fs(value) __loadsegment_simple(fs, (value))
280 #define __loadsegment_gs(value) __loadsegment_simple(gs, (value))
281 
282 #else
283 
284 static inline void __loadsegment_fs(unsigned short value)
285 {
286         asm volatile("                                          \n"
287                      "1:        movw %0, %%fs                   \n"
288                      "2:                                        \n"
289 
290                      _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_clear_fs)
291 
292                      : : "rm" (value) : "memory");
293 }
294 
295 /* __loadsegment_gs is intentionally undefined.  Use load_gs_index instead. */
296 
297 #endif
298 
299 #define loadsegment(seg, value) __loadsegment_ ## seg (value)
300 
301 /*
302  * Save a segment register away:
303  */
304 #define savesegment(seg, value)                         \
305         asm("mov %%" #seg ",%0":"=r" (value) : : "memory")
306 
307 /*
308  * x86-32 user GS accessors:
309  */
310 #ifdef CONFIG_X86_32
311 # ifdef CONFIG_X86_32_LAZY_GS
312 #  define get_user_gs(regs)             (u16)({ unsigned long v; savesegment(gs, v); v; })
313 #  define set_user_gs(regs, v)          loadsegment(gs, (unsigned long)(v))
314 #  define task_user_gs(tsk)             ((tsk)->thread.gs)
315 #  define lazy_save_gs(v)               savesegment(gs, (v))
316 #  define lazy_load_gs(v)               loadsegment(gs, (v))
317 # else  /* X86_32_LAZY_GS */
318 #  define get_user_gs(regs)             (u16)((regs)->gs)
319 #  define set_user_gs(regs, v)          do { (regs)->gs = (v); } while (0)
320 #  define task_user_gs(tsk)             (task_pt_regs(tsk)->gs)
321 #  define lazy_save_gs(v)               do { } while (0)
322 #  define lazy_load_gs(v)               do { } while (0)
323 # endif /* X86_32_LAZY_GS */
324 #endif  /* X86_32 */
325 
326 #endif /* !__ASSEMBLY__ */
327 #endif /* __KERNEL__ */
328 
329 #endif /* _ASM_X86_SEGMENT_H */
330 

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