arch/x86/include/asm/segment.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_X86_SEGMENT_H
   3 #define _ASM_X86_SEGMENT_H
   4
   5 #include <linux/const.h>
   6 #include <asm/alternative.h>
   7
   8 /*
   9  * Constructor for a conventional segment GDT (or LDT) entry.
  10  * This is a macro so it can be used in initializers.
  11  */
  12 #define GDT_ENTRY(flags, base, limit)                   \
  13         ((((base)  & _AC(0xff000000,ULL)) << (56-24)) | \
  14          (((flags) & _AC(0x0000f0ff,ULL)) << 40) |      \
  15          (((limit) & _AC(0x000f0000,ULL)) << (48-16)) | \
  16          (((base)  & _AC(0x00ffffff,ULL)) << 16) |      \
  17          (((limit) & _AC(0x0000ffff,ULL))))
  18
  19 /* Simple and small GDT entries for booting only: */
  20
  21 #define GDT_ENTRY_BOOT_CS       2
  22 #define GDT_ENTRY_BOOT_DS       3
  23 #define GDT_ENTRY_BOOT_TSS      4
  24 #define __BOOT_CS               (GDT_ENTRY_BOOT_CS*8)
  25 #define __BOOT_DS               (GDT_ENTRY_BOOT_DS*8)
  26 #define __BOOT_TSS              (GDT_ENTRY_BOOT_TSS*8)
  27
  28 /*
  29  * Bottom two bits of selector give the ring
  30  * privilege level
  31  */
  32 #define SEGMENT_RPL_MASK        0x3
  33
  34 /* User mode is privilege level 3: */
  35 #define USER_RPL                0x3
  36
  37 /* Bit 2 is Table Indicator (TI): selects between LDT or GDT */
  38 #define SEGMENT_TI_MASK         0x4
  39 /* LDT segment has TI set ... */
  40 #define SEGMENT_LDT             0x4
  41 /* ... GDT has it cleared */
  42 #define SEGMENT_GDT             0x0
  43
  44 #define GDT_ENTRY_INVALID_SEG   0
  45
  46 #ifdef CONFIG_X86_32
  47 /*
  48  * The layout of the per-CPU GDT under Linux:
  49  *
  50  *   0 - null                                                           <=== cacheline #1
  51  *   1 - reserved
  52  *   2 - reserved
  53  *   3 - reserved
  54  *
  55  *   4 - unused                                                         <=== cacheline #2
  56  *   5 - unused
  57  *
  58  *  ------- start of TLS (Thread-Local Storage) segments:
  59  *
  60  *   6 - TLS segment #1                 [ glibc's TLS segment ]
  61  *   7 - TLS segment #2                 [ Wine's %fs Win32 segment ]
  62  *   8 - TLS segment #3                                                 <=== cacheline #3
  63  *   9 - reserved
  64  *  10 - reserved
  65  *  11 - reserved
  66  *
  67  *  ------- start of kernel segments:
  68  *
  69  *  12 - kernel code segment                                            <=== cacheline #4
  70  *  13 - kernel data segment
  71  *  14 - default user CS
  72  *  15 - default user DS
  73  *  16 - TSS                                                            <=== cacheline #5
  74  *  17 - LDT
  75  *  18 - PNPBIOS support (16->32 gate)
  76  *  19 - PNPBIOS support
  77  *  20 - PNPBIOS support                                                <=== cacheline #6
  78  *  21 - PNPBIOS support
  79  *  22 - PNPBIOS support
  80  *  23 - APM BIOS support
  81  *  24 - APM BIOS support                                               <=== cacheline #7
  82  *  25 - APM BIOS support
  83  *
  84  *  26 - ESPFIX small SS
  85  *  27 - per-cpu                        [ offset to per-cpu data area ]
  86  *  28 - stack_canary-20                [ for stack protector ]         <=== cacheline #8
  87  *  29 - unused
  88  *  30 - unused
  89  *  31 - TSS for double fault handler
  90  */
  91 #define GDT_ENTRY_TLS_MIN               6
  92 #define GDT_ENTRY_TLS_MAX               (GDT_ENTRY_TLS_MIN + GDT_ENTRY_TLS_ENTRIES - 1)
  93
  94 #define GDT_ENTRY_KERNEL_CS             12
  95 #define GDT_ENTRY_KERNEL_DS             13
  96 #define GDT_ENTRY_DEFAULT_USER_CS       14
  97 #define GDT_ENTRY_DEFAULT_USER_DS       15
  98 #define GDT_ENTRY_TSS                   16
  99 #define GDT_ENTRY_LDT                   17
 100 #define GDT_ENTRY_PNPBIOS_CS32          18
 101 #define GDT_ENTRY_PNPBIOS_CS16          19
 102 #define GDT_ENTRY_PNPBIOS_DS            20
 103 #define GDT_ENTRY_PNPBIOS_TS1           21
 104 #define GDT_ENTRY_PNPBIOS_TS2           22
 105 #define GDT_ENTRY_APMBIOS_BASE          23
 106
 107 #define GDT_ENTRY_ESPFIX_SS             26
 108 #define GDT_ENTRY_PERCPU                27
 109 #define GDT_ENTRY_STACK_CANARY          28
 110
 111 #define GDT_ENTRY_DOUBLEFAULT_TSS       31
 112
 113 /*
 114  * Number of entries in the GDT table:
 115  */
 116 #define GDT_ENTRIES                     32
 117
 118 /*
 119  * Segment selector values corresponding to the above entries:
 120  */
 121
 122 #define __KERNEL_CS                     (GDT_ENTRY_KERNEL_CS*8)
 123 #define __KERNEL_DS                     (GDT_ENTRY_KERNEL_DS*8)
 124 #define __USER_DS                       (GDT_ENTRY_DEFAULT_USER_DS*8 + 3)
 125 #define __USER_CS                       (GDT_ENTRY_DEFAULT_USER_CS*8 + 3)
 126 #define __ESPFIX_SS                     (GDT_ENTRY_ESPFIX_SS*8)
 127
 128 /* segment for calling fn: */
 129 #define PNP_CS32                        (GDT_ENTRY_PNPBIOS_CS32*8)
 130 /* code segment for BIOS: */
 131 #define PNP_CS16                        (GDT_ENTRY_PNPBIOS_CS16*8)
 132
 133 /* "Is this PNP code selector (PNP_CS32 or PNP_CS16)?" */
 134 #define SEGMENT_IS_PNP_CODE(x)          (((x) & 0xf4) == PNP_CS32)
 135
 136 /* data segment for BIOS: */
 137 #define PNP_DS                          (GDT_ENTRY_PNPBIOS_DS*8)
 138 /* transfer data segment: */
 139 #define PNP_TS1                         (GDT_ENTRY_PNPBIOS_TS1*8)
 140 /* another data segment: */
 141 #define PNP_TS2                         (GDT_ENTRY_PNPBIOS_TS2*8)
 142
 143 #ifdef CONFIG_SMP
 144 # define __KERNEL_PERCPU                (GDT_ENTRY_PERCPU*8)
 145 #else
 146 # define __KERNEL_PERCPU                0
 147 #endif
 148
 149 #ifdef CONFIG_CC_STACKPROTECTOR
 150 # define __KERNEL_STACK_CANARY          (GDT_ENTRY_STACK_CANARY*8)
 151 #else
 152 # define __KERNEL_STACK_CANARY          0
 153 #endif
 154
 155 #else /* 64-bit: */
 156
 157 #include <asm/cache.h>
 158
 159 #define GDT_ENTRY_KERNEL32_CS           1
 160 #define GDT_ENTRY_KERNEL_CS             2
 161 #define GDT_ENTRY_KERNEL_DS             3
 162
 163 /*
 164  * We cannot use the same code segment descriptor for user and kernel mode,
 165  * not even in long flat mode, because of different DPL.
 166  *
 167  * GDT layout to get 64-bit SYSCALL/SYSRET support right. SYSRET hardcodes
 168  * selectors:
 169  *
 170  *   if returning to 32-bit userspace: cs = STAR.SYSRET_CS,
 171  *   if returning to 64-bit userspace: cs = STAR.SYSRET_CS+16,
 172  *
 173  * ss = STAR.SYSRET_CS+8 (in either case)
 174  *
 175  * thus USER_DS should be between 32-bit and 64-bit code selectors:
 176  */
 177 #define GDT_ENTRY_DEFAULT_USER32_CS     4
 178 #define GDT_ENTRY_DEFAULT_USER_DS       5
 179 #define GDT_ENTRY_DEFAULT_USER_CS       6
 180
 181 /* Needs two entries */
 182 #define GDT_ENTRY_TSS                   8
 183 /* Needs two entries */
 184 #define GDT_ENTRY_LDT                   10
 185
 186 #define GDT_ENTRY_TLS_MIN               12
 187 #define GDT_ENTRY_TLS_MAX               14
 188
 189 /* Abused to load per CPU data from limit */
 190 #define GDT_ENTRY_PER_CPU               15
 191
 192 /*
 193  * Number of entries in the GDT table:
 194  */
 195 #define GDT_ENTRIES                     16
 196
 197 /*
 198  * Segment selector values corresponding to the above entries:
 199  *
 200  * Note, selectors also need to have a correct RPL,
 201  * expressed with the +3 value for user-space selectors:
 202  */
 203 #define __KERNEL32_CS                   (GDT_ENTRY_KERNEL32_CS*8)
 204 #define __KERNEL_CS                     (GDT_ENTRY_KERNEL_CS*8)
 205 #define __KERNEL_DS                     (GDT_ENTRY_KERNEL_DS*8)
 206 #define __USER32_CS                     (GDT_ENTRY_DEFAULT_USER32_CS*8 + 3)
 207 #define __USER_DS                       (GDT_ENTRY_DEFAULT_USER_DS*8 + 3)
 208 #define __USER32_DS                     __USER_DS
 209 #define __USER_CS                       (GDT_ENTRY_DEFAULT_USER_CS*8 + 3)
 210 #define __PER_CPU_SEG                   (GDT_ENTRY_PER_CPU*8 + 3)
 211
 212 #endif
 213
 214 #ifndef CONFIG_PARAVIRT
 215 # define get_kernel_rpl()               0
 216 #endif
 217
 218 #define IDT_ENTRIES                     256
 219 #define NUM_EXCEPTION_VECTORS           32
 220
 221 /* Bitmask of exception vectors which push an error code on the stack: */
 222 #define EXCEPTION_ERRCODE_MASK          0x00027d00
 223
 224 #define GDT_SIZE                        (GDT_ENTRIES*8)
 225 #define GDT_ENTRY_TLS_ENTRIES           3
 226 #define TLS_SIZE                        (GDT_ENTRY_TLS_ENTRIES* 8)
 227
 228 #ifdef __KERNEL__
 229
 230 /*
 231  * early_idt_handler_array is an array of entry points referenced in the
 232  * early IDT.  For simplicity, it's a real array with one entry point
 233  * every nine bytes.  That leaves room for an optional 'push $0' if the
 234  * vector has no error code (two bytes), a 'push $vector_number' (two
 235  * bytes), and a jump to the common entry code (up to five bytes).
 236  */
 237 #define EARLY_IDT_HANDLER_SIZE 9
 238
 239 #ifndef __ASSEMBLY__
 240
 241 extern const char early_idt_handler_array[NUM_EXCEPTION_VECTORS][EARLY_IDT_HANDLER_SIZE];
 242 extern void early_ignore_irq(void);
 243
 244 /*
 245  * Load a segment. Fall back on loading the zero segment if something goes
 246  * wrong.  This variant assumes that loading zero fully clears the segment.
 247  * This is always the case on Intel CPUs and, even on 64-bit AMD CPUs, any
 248  * failure to fully clear the cached descriptor is only observable for
 249  * FS and GS.
 250  */
 251 #define __loadsegment_simple(seg, value)                                \
 252 do {                                                                    \
 253         unsigned short __val = (value);                                 \
 254                                                                         \
 255         asm volatile("                                          \n"     \
 256                      "1:        movl %k0,%%" #seg "             \n"     \
 257                                                                         \
 258                      ".section .fixup,\"ax\"                    \n"     \
 259                      "2:        xorl %k0,%k0                    \n"     \
 260                      "          jmp 1b                          \n"     \
 261                      ".previous                                 \n"     \
 262                                                                         \
 263                      _ASM_EXTABLE(1b, 2b)                               \
 264                                                                         \
 265                      : "+r" (__val) : : "memory");                      \
 266 } while (0)
 267
 268 #define __loadsegment_ss(value) __loadsegment_simple(ss, (value))
 269 #define __loadsegment_ds(value) __loadsegment_simple(ds, (value))
 270 #define __loadsegment_es(value) __loadsegment_simple(es, (value))
 271
 272 #ifdef CONFIG_X86_32
 273
 274 /*
 275  * On 32-bit systems, the hidden parts of FS and GS are unobservable if
 276  * the selector is NULL, so there's no funny business here.
 277  */
 278 #define __loadsegment_fs(value) __loadsegment_simple(fs, (value))
 279 #define __loadsegment_gs(value) __loadsegment_simple(gs, (value))
 280
 281 #else
 282
 283 static inline void __loadsegment_fs(unsigned short value)
 284 {
 285         asm volatile("                                          \n"
 286                      "1:        movw %0, %%fs                   \n"
 287                      "2:                                        \n"
 288
 289                      _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_clear_fs)
 290
 291                      : : "rm" (value) : "memory");
 292 }
 293
 294 /* __loadsegment_gs is intentionally undefined.  Use load_gs_index instead. */
 295
 296 #endif
 297
 298 #define loadsegment(seg, value) __loadsegment_ ## seg (value)
 299
 300 /*
 301  * Save a segment register away:
 302  */
 303 #define savesegment(seg, value)                         \
 304         asm("mov %%" #seg ",%0":"=r" (value) : : "memory")
 305
 306 /*
 307  * x86-32 user GS accessors:
 308  */
 309 #ifdef CONFIG_X86_32
 310 # ifdef CONFIG_X86_32_LAZY_GS
 311 #  define get_user_gs(regs)             (u16)({ unsigned long v; savesegment(gs, v); v; })
 312 #  define set_user_gs(regs, v)          loadsegment(gs, (unsigned long)(v))
 313 #  define task_user_gs(tsk)             ((tsk)->thread.gs)
 314 #  define lazy_save_gs(v)               savesegment(gs, (v))
 315 #  define lazy_load_gs(v)               loadsegment(gs, (v))
 316 # else  /* X86_32_LAZY_GS */
 317 #  define get_user_gs(regs)             (u16)((regs)->gs)
 318 #  define set_user_gs(regs, v)          do { (regs)->gs = (v); } while (0)
 319 #  define task_user_gs(tsk)             (task_pt_regs(tsk)->gs)
 320 #  define lazy_save_gs(v)               do { } while (0)
 321 #  define lazy_load_gs(v)               do { } while (0)
 322 # endif /* X86_32_LAZY_GS */
 323 #endif  /* X86_32 */
 324
 325 #endif /* !__ASSEMBLY__ */
 326 #endif /* __KERNEL__ */
 327
 328 #endif /* _ASM_X86_SEGMENT_H */