LXR 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
 240extern 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)                                \
 253do {                                                                    \
 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
 284static 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