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 */