arch/x86/include/asm/desc.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_X86_DESC_H
   3 #define _ASM_X86_DESC_H
   4
   5 #include <asm/desc_defs.h>
   6 #include <asm/ldt.h>
   7 #include <asm/mmu.h>
   8 #include <asm/fixmap.h>
   9 #include <asm/irq_vectors.h>
  10 #include <asm/cpu_entry_area.h>
  11
  12 #include <linux/smp.h>
  13 #include <linux/percpu.h>
  14
  15 static inline void fill_ldt(struct desc_struct *desc, const struct user_desc *info)
  16 {
  17         desc->limit0            = info->limit & 0x0ffff;
  18
  19         desc->base0             = (info->base_addr & 0x0000ffff);
  20         desc->base1             = (info->base_addr & 0x00ff0000) >> 16;
  21
  22         desc->type              = (info->read_exec_only ^ 1) << 1;
  23         desc->type             |= info->contents << 2;
  24         /* Set the ACCESS bit so it can be mapped RO */
  25         desc->type             |= 1;
  26
  27         desc->s                 = 1;
  28         desc->dpl               = 0x3;
  29         desc->p                 = info->seg_not_present ^ 1;
  30         desc->limit1            = (info->limit & 0xf0000) >> 16;
  31         desc->avl               = info->useable;
  32         desc->d                 = info->seg_32bit;
  33         desc->g                 = info->limit_in_pages;
  34
  35         desc->base2             = (info->base_addr & 0xff000000) >> 24;
  36         /*
  37          * Don't allow setting of the lm bit. It would confuse
  38          * user_64bit_mode and would get overridden by sysret anyway.
  39          */
  40         desc->l                 = 0;
  41 }
  42
  43 extern struct desc_ptr idt_descr;
  44 extern gate_desc idt_table[];
  45 extern const struct desc_ptr debug_idt_descr;
  46 extern gate_desc debug_idt_table[];
  47
  48 struct gdt_page {
  49         struct desc_struct gdt[GDT_ENTRIES];
  50 } __attribute__((aligned(PAGE_SIZE)));
  51
  52 DECLARE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page);
  53
  54 /* Provide the original GDT */
  55 static inline struct desc_struct *get_cpu_gdt_rw(unsigned int cpu)
  56 {
  57         return per_cpu(gdt_page, cpu).gdt;
  58 }
  59
  60 /* Provide the current original GDT */
  61 static inline struct desc_struct *get_current_gdt_rw(void)
  62 {
  63         return this_cpu_ptr(&gdt_page)->gdt;
  64 }
  65
  66 /* Provide the fixmap address of the remapped GDT */
  67 static inline struct desc_struct *get_cpu_gdt_ro(int cpu)
  68 {
  69         return (struct desc_struct *)&get_cpu_entry_area(cpu)->gdt;
  70 }
  71
  72 /* Provide the current read-only GDT */
  73 static inline struct desc_struct *get_current_gdt_ro(void)
  74 {
  75         return get_cpu_gdt_ro(smp_processor_id());
  76 }
  77
  78 /* Provide the physical address of the GDT page. */
  79 static inline phys_addr_t get_cpu_gdt_paddr(unsigned int cpu)
  80 {
  81         return per_cpu_ptr_to_phys(get_cpu_gdt_rw(cpu));
  82 }
  83
  84 static inline void pack_gate(gate_desc *gate, unsigned type, unsigned long func,
  85                              unsigned dpl, unsigned ist, unsigned seg)
  86 {
  87         gate->offset_low        = (u16) func;
  88         gate->bits.p            = 1;
  89         gate->bits.dpl          = dpl;
  90         gate->bits.zero         = 0;
  91         gate->bits.type         = type;
  92         gate->offset_middle     = (u16) (func >> 16);
  93 #ifdef CONFIG_X86_64
  94         gate->segment           = __KERNEL_CS;
  95         gate->bits.ist          = ist;
  96         gate->reserved          = 0;
  97         gate->offset_high       = (u32) (func >> 32);
  98 #else
  99         gate->segment           = seg;
 100         gate->bits.ist          = 0;
 101 #endif
 102 }
 103
 104 static inline int desc_empty(const void *ptr)
 105 {
 106         const u32 *desc = ptr;
 107
 108         return !(desc[0] | desc[1]);
 109 }
 110
 111 #ifdef CONFIG_PARAVIRT
 112 #include <asm/paravirt.h>
 113 #else
 114 #define load_TR_desc()                          native_load_tr_desc()
 115 #define load_gdt(dtr)                           native_load_gdt(dtr)
 116 #define load_idt(dtr)                           native_load_idt(dtr)
 117 #define load_tr(tr)                             asm volatile("ltr %0"::"m" (tr))
 118 #define load_ldt(ldt)                           asm volatile("lldt %0"::"m" (ldt))
 119
 120 #define store_gdt(dtr)                          native_store_gdt(dtr)
 121 #define store_tr(tr)                            (tr = native_store_tr())
 122
 123 #define load_TLS(t, cpu)                        native_load_tls(t, cpu)
 124 #define set_ldt                                 native_set_ldt
 125
 126 #define write_ldt_entry(dt, entry, desc)        native_write_ldt_entry(dt, entry, desc)
 127 #define write_gdt_entry(dt, entry, desc, type)  native_write_gdt_entry(dt, entry, desc, type)
 128 #define write_idt_entry(dt, entry, g)           native_write_idt_entry(dt, entry, g)
 129
 130 static inline void paravirt_alloc_ldt(struct desc_struct *ldt, unsigned entries)
 131 {
 132 }
 133
 134 static inline void paravirt_free_ldt(struct desc_struct *ldt, unsigned entries)
 135 {
 136 }
 137 #endif  /* CONFIG_PARAVIRT */
 138
 139 #define store_ldt(ldt) asm("sldt %0" : "=m"(ldt))
 140
 141 static inline void native_write_idt_entry(gate_desc *idt, int entry, const gate_desc *gate)
 142 {
 143         memcpy(&idt[entry], gate, sizeof(*gate));
 144 }
 145
 146 static inline void native_write_ldt_entry(struct desc_struct *ldt, int entry, const void *desc)
 147 {
 148         memcpy(&ldt[entry], desc, 8);
 149 }
 150
 151 static inline void
 152 native_write_gdt_entry(struct desc_struct *gdt, int entry, const void *desc, int type)
 153 {
 154         unsigned int size;
 155
 156         switch (type) {
 157         case DESC_TSS:  size = sizeof(tss_desc);        break;
 158         case DESC_LDT:  size = sizeof(ldt_desc);        break;
 159         default:        size = sizeof(*gdt);            break;
 160         }
 161
 162         memcpy(&gdt[entry], desc, size);
 163 }
 164
 165 static inline void set_tssldt_descriptor(void *d, unsigned long addr,
 166                                          unsigned type, unsigned size)
 167 {
 168         struct ldttss_desc *desc = d;
 169
 170         memset(desc, 0, sizeof(*desc));
 171
 172         desc->limit0            = (u16) size;
 173         desc->base0             = (u16) addr;
 174         desc->base1             = (addr >> 16) & 0xFF;
 175         desc->type              = type;
 176         desc->p                 = 1;
 177         desc->limit1            = (size >> 16) & 0xF;
 178         desc->base2             = (addr >> 24) & 0xFF;
 179 #ifdef CONFIG_X86_64
 180         desc->base3             = (u32) (addr >> 32);
 181 #endif
 182 }
 183
 184 static inline void __set_tss_desc(unsigned cpu, unsigned int entry, struct x86_hw_tss *addr)
 185 {
 186         struct desc_struct *d = get_cpu_gdt_rw(cpu);
 187         tss_desc tss;
 188
 189         set_tssldt_descriptor(&tss, (unsigned long)addr, DESC_TSS,
 190                               __KERNEL_TSS_LIMIT);
 191         write_gdt_entry(d, entry, &tss, DESC_TSS);
 192 }
 193
 194 #define set_tss_desc(cpu, addr) __set_tss_desc(cpu, GDT_ENTRY_TSS, addr)
 195
 196 static inline void native_set_ldt(const void *addr, unsigned int entries)
 197 {
 198         if (likely(entries == 0))
 199                 asm volatile("lldt %w0"::"q" (0));
 200         else {
 201                 unsigned cpu = smp_processor_id();
 202                 ldt_desc ldt;
 203
 204                 set_tssldt_descriptor(&ldt, (unsigned long)addr, DESC_LDT,
 205                                       entries * LDT_ENTRY_SIZE - 1);
 206                 write_gdt_entry(get_cpu_gdt_rw(cpu), GDT_ENTRY_LDT,
 207                                 &ldt, DESC_LDT);
 208                 asm volatile("lldt %w0"::"q" (GDT_ENTRY_LDT*8));
 209         }
 210 }
 211
 212 static inline void native_load_gdt(const struct desc_ptr *dtr)
 213 {
 214         asm volatile("lgdt %0"::"m" (*dtr));
 215 }
 216
 217 static inline void native_load_idt(const struct desc_ptr *dtr)
 218 {
 219         asm volatile("lidt %0"::"m" (*dtr));
 220 }
 221
 222 static inline void native_store_gdt(struct desc_ptr *dtr)
 223 {
 224         asm volatile("sgdt %0":"=m" (*dtr));
 225 }
 226
 227 static inline void store_idt(struct desc_ptr *dtr)
 228 {
 229         asm volatile("sidt %0":"=m" (*dtr));
 230 }
 231
 232 /*
 233  * The LTR instruction marks the TSS GDT entry as busy. On 64-bit, the GDT is
 234  * a read-only remapping. To prevent a page fault, the GDT is switched to the
 235  * original writeable version when needed.
 236  */
 237 #ifdef CONFIG_X86_64
 238 static inline void native_load_tr_desc(void)
 239 {
 240         struct desc_ptr gdt;
 241         int cpu = raw_smp_processor_id();
 242         bool restore = 0;
 243         struct desc_struct *fixmap_gdt;
 244
 245         native_store_gdt(&gdt);
 246         fixmap_gdt = get_cpu_gdt_ro(cpu);
 247
 248         /*
 249          * If the current GDT is the read-only fixmap, swap to the original
 250          * writeable version. Swap back at the end.
 251          */
 252         if (gdt.address == (unsigned long)fixmap_gdt) {
 253                 load_direct_gdt(cpu);
 254                 restore = 1;
 255         }
 256         asm volatile("ltr %w0"::"q" (GDT_ENTRY_TSS*8));
 257         if (restore)
 258                 load_fixmap_gdt(cpu);
 259 }
 260 #else
 261 static inline void native_load_tr_desc(void)
 262 {
 263         asm volatile("ltr %w0"::"q" (GDT_ENTRY_TSS*8));
 264 }
 265 #endif
 266
 267 static inline unsigned long native_store_tr(void)
 268 {
 269         unsigned long tr;
 270
 271         asm volatile("str %0":"=r" (tr));
 272
 273         return tr;
 274 }
 275
 276 static inline void native_load_tls(struct thread_struct *t, unsigned int cpu)
 277 {
 278         struct desc_struct *gdt = get_cpu_gdt_rw(cpu);
 279         unsigned int i;
 280
 281         for (i = 0; i < GDT_ENTRY_TLS_ENTRIES; i++)
 282                 gdt[GDT_ENTRY_TLS_MIN + i] = t->tls_array[i];
 283 }
 284
 285 DECLARE_PER_CPU(bool, __tss_limit_invalid);
 286
 287 static inline void force_reload_TR(void)
 288 {
 289         struct desc_struct *d = get_current_gdt_rw();
 290         tss_desc tss;
 291
 292         memcpy(&tss, &d[GDT_ENTRY_TSS], sizeof(tss_desc));
 293
 294         /*
 295          * LTR requires an available TSS, and the TSS is currently
 296          * busy.  Make it be available so that LTR will work.
 297          */
 298         tss.type = DESC_TSS;
 299         write_gdt_entry(d, GDT_ENTRY_TSS, &tss, DESC_TSS);
 300
 301         load_TR_desc();
 302         this_cpu_write(__tss_limit_invalid, false);
 303 }
 304
 305 /*
 306  * Call this if you need the TSS limit to be correct, which should be the case
 307  * if and only if you have TIF_IO_BITMAP set or you're switching to a task
 308  * with TIF_IO_BITMAP set.
 309  */
 310 static inline void refresh_tss_limit(void)
 311 {
 312         DEBUG_LOCKS_WARN_ON(preemptible());
 313
 314         if (unlikely(this_cpu_read(__tss_limit_invalid)))
 315                 force_reload_TR();
 316 }
 317
 318 /*
 319  * If you do something evil that corrupts the cached TSS limit (I'm looking
 320  * at you, VMX exits), call this function.
 321  *
 322  * The optimization here is that the TSS limit only matters for Linux if the
 323  * IO bitmap is in use.  If the TSS limit gets forced to its minimum value,
 324  * everything works except that IO bitmap will be ignored and all CPL 3 IO
 325  * instructions will #GP, which is exactly what we want for normal tasks.
 326  */
 327 static inline void invalidate_tss_limit(void)
 328 {
 329         DEBUG_LOCKS_WARN_ON(preemptible());
 330
 331         if (unlikely(test_thread_flag(TIF_IO_BITMAP)))
 332                 force_reload_TR();
 333         else
 334                 this_cpu_write(__tss_limit_invalid, true);
 335 }
 336
 337 /* This intentionally ignores lm, since 32-bit apps don't have that field. */
 338 #define LDT_empty(info)                                 \
 339         ((info)->base_addr              == 0    &&      \
 340          (info)->limit                  == 0    &&      \
 341          (info)->contents               == 0    &&      \
 342          (info)->read_exec_only         == 1    &&      \
 343          (info)->seg_32bit              == 0    &&      \
 344          (info)->limit_in_pages         == 0    &&      \
 345          (info)->seg_not_present        == 1    &&      \
 346          (info)->useable                == 0)
 347
 348 /* Lots of programs expect an all-zero user_desc to mean "no segment at all". */
 349 static inline bool LDT_zero(const struct user_desc *info)
 350 {
 351         return (info->base_addr         == 0 &&
 352                 info->limit             == 0 &&
 353                 info->contents          == 0 &&
 354                 info->read_exec_only    == 0 &&
 355                 info->seg_32bit         == 0 &&
 356                 info->limit_in_pages    == 0 &&
 357                 info->seg_not_present   == 0 &&
 358                 info->useable           == 0);
 359 }
 360
 361 static inline void clear_LDT(void)
 362 {
 363         set_ldt(NULL, 0);
 364 }
 365
 366 static inline unsigned long get_desc_base(const struct desc_struct *desc)
 367 {
 368         return (unsigned)(desc->base0 | ((desc->base1) << 16) | ((desc->base2) << 24));
 369 }
 370
 371 static inline void set_desc_base(struct desc_struct *desc, unsigned long base)
 372 {
 373         desc->base0 = base & 0xffff;
 374         desc->base1 = (base >> 16) & 0xff;
 375         desc->base2 = (base >> 24) & 0xff;
 376 }
 377
 378 static inline unsigned long get_desc_limit(const struct desc_struct *desc)
 379 {
 380         return desc->limit0 | (desc->limit1 << 16);
 381 }
 382
 383 static inline void set_desc_limit(struct desc_struct *desc, unsigned long limit)
 384 {
 385         desc->limit0 = limit & 0xffff;
 386         desc->limit1 = (limit >> 16) & 0xf;
 387 }
 388
 389 void update_intr_gate(unsigned int n, const void *addr);
 390 void alloc_intr_gate(unsigned int n, const void *addr);
 391
 392 extern unsigned long system_vectors[];
 393
 394 #ifdef CONFIG_X86_64
 395 DECLARE_PER_CPU(u32, debug_idt_ctr);
 396 static inline bool is_debug_idt_enabled(void)
 397 {
 398         if (this_cpu_read(debug_idt_ctr))
 399                 return true;
 400
 401         return false;
 402 }
 403
 404 static inline void load_debug_idt(void)
 405 {
 406         load_idt((const struct desc_ptr *)&debug_idt_descr);
 407 }
 408 #else
 409 static inline bool is_debug_idt_enabled(void)
 410 {
 411         return false;
 412 }
 413
 414 static inline void load_debug_idt(void)
 415 {
 416 }
 417 #endif
 418
 419 /*
 420  * The load_current_idt() must be called with interrupts disabled
 421  * to avoid races. That way the IDT will always be set back to the expected
 422  * descriptor. It's also called when a CPU is being initialized, and
 423  * that doesn't need to disable interrupts, as nothing should be
 424  * bothering the CPU then.
 425  */
 426 static inline void load_current_idt(void)
 427 {
 428         if (is_debug_idt_enabled())
 429                 load_debug_idt();
 430         else
 431                 load_idt((const struct desc_ptr *)&idt_descr);
 432 }
 433
 434 extern void idt_setup_early_handler(void);
 435 extern void idt_setup_early_traps(void);
 436 extern void idt_setup_traps(void);
 437 extern void idt_setup_apic_and_irq_gates(void);
 438
 439 #ifdef CONFIG_X86_64
 440 extern void idt_setup_early_pf(void);
 441 extern void idt_setup_ist_traps(void);
 442 extern void idt_setup_debugidt_traps(void);
 443 #else
 444 static inline void idt_setup_early_pf(void) { }
 445 static inline void idt_setup_ist_traps(void) { }
 446 static inline void idt_setup_debugidt_traps(void) { }
 447 #endif
 448
 449 extern void idt_invalidate(void *addr);
 450
 451 #endif /* _ASM_X86_DESC_H */