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