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
  11 #include <linux/smp.h>
  12 #include <linux/percpu.h>
  13
  14 static inline void fill_ldt(struct desc_struct *desc, const struct user_desc *info)
  15 {
  16         desc->limit0            = info->limit & 0x0ffff;
  17
  18         desc->base0             = (info->base_addr & 0x0000ffff);
  19         desc->base1             = (info->base_addr & 0x00ff0000) >> 16;
  20
  21         desc->type              = (info->read_exec_only ^ 1) << 1;
  22         desc->type             |= info->contents << 2;
  23
  24         desc->s                 = 1;
  25         desc->dpl               = 0x3;
  26         desc->p                 = info->seg_not_present ^ 1;
  27         desc->limit1            = (info->limit & 0xf0000) >> 16;
  28         desc->avl               = info->useable;
  29         desc->d                 = info->seg_32bit;
  30         desc->g                 = info->limit_in_pages;
  31
  32         desc->base2             = (info->base_addr & 0xff000000) >> 24;
  33         /*
  34          * Don't allow setting of the lm bit. It would confuse
  35          * user_64bit_mode and would get overridden by sysret anyway.
  36          */
  37         desc->l                 = 0;
  38 }
  39
  40 extern struct desc_ptr idt_descr;
  41 extern gate_desc idt_table[];
  42 extern const struct desc_ptr debug_idt_descr;
  43 extern gate_desc debug_idt_table[];
  44
  45 struct gdt_page {
  46         struct desc_struct gdt[GDT_ENTRIES];
  47 } __attribute__((aligned(PAGE_SIZE)));
  48
  49 DECLARE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page);
  50
  51 /* Provide the original GDT */
  52 static inline struct desc_struct *get_cpu_gdt_rw(unsigned int cpu)
  53 {
  54         return per_cpu(gdt_page, cpu).gdt;
  55 }
  56
  57 /* Provide the current original GDT */
  58 static inline struct desc_struct *get_current_gdt_rw(void)
  59 {
  60         return this_cpu_ptr(&gdt_page)->gdt;
  61 }
  62
  63 /* Get the fixmap index for a specific processor */
  64 static inline unsigned int get_cpu_gdt_ro_index(int cpu)
  65 {
  66         return FIX_GDT_REMAP_BEGIN + cpu;
  67 }
  68
  69 /* Provide the fixmap address of the remapped GDT */
  70 static inline struct desc_struct *get_cpu_gdt_ro(int cpu)
  71 {
  72         unsigned int idx = get_cpu_gdt_ro_index(cpu);
  73         return (struct desc_struct *)__fix_to_virt(idx);
  74 }
  75
  76 /* Provide the current read-only GDT */
  77 static inline struct desc_struct *get_current_gdt_ro(void)
  78 {
  79         return get_cpu_gdt_ro(smp_processor_id());
  80 }
  81
  82 /* Provide the physical address of the GDT page. */
  83 static inline phys_addr_t get_cpu_gdt_paddr(unsigned int cpu)
  84 {
  85         return per_cpu_ptr_to_phys(get_cpu_gdt_rw(cpu));
  86 }
  87
  88 static inline void pack_gate(gate_desc *gate, unsigned type, unsigned long func,
  89                              unsigned dpl, unsigned ist, unsigned seg)
  90 {
  91         gate->offset_low        = (u16) func;
  92         gate->bits.p            = 1;
  93         gate->bits.dpl          = dpl;
  94         gate->bits.zero         = 0;
  95         gate->bits.type         = type;
  96         gate->offset_middle     = (u16) (func >> 16);
  97 #ifdef CONFIG_X86_64
  98         gate->segment           = __KERNEL_CS;
  99         gate->bits.ist          = ist;
 100         gate->reserved          = 0;
 101         gate->offset_high       = (u32) (func >> 32);
 102 #else
 103         gate->segment           = seg;
 104         gate->bits.ist          = 0;
 105 #endif
 106 }
 107
 108 static inline int desc_empty(const void *ptr)
 109 {
 110         const u32 *desc = ptr;
 111
 112         return !(desc[0] | desc[1]);
 113 }
 114
 115 #ifdef CONFIG_PARAVIRT
 116 #include <asm/paravirt.h>
 117 #else
 118 #define load_TR_desc()                          native_load_tr_desc()
 119 #define load_gdt(dtr)                           native_load_gdt(dtr)
 120 #define load_idt(dtr)                           native_load_idt(dtr)
 121 #define load_tr(tr)                             asm volatile("ltr %0"::"m" (tr))
 122 #define load_ldt(ldt)                           asm volatile("lldt %0"::"m" (ldt))
 123
 124 #define store_gdt(dtr)                          native_store_gdt(dtr)
 125 #define store_tr(tr)                            (tr = native_store_tr())
 126
 127 #define load_TLS(t, cpu)                        native_load_tls(t, cpu)
 128 #define set_ldt                                 native_set_ldt
 129
 130 #define write_ldt_entry(dt, entry, desc)        native_write_ldt_entry(dt, entry, desc)
 131 #define write_gdt_entry(dt, entry, desc, type)  native_write_gdt_entry(dt, entry, desc, type)
 132 #define write_idt_entry(dt, entry, g)           native_write_idt_entry(dt, entry, g)
 133
 134 static inline void paravirt_alloc_ldt(struct desc_struct *ldt, unsigned entries)
 135 {
 136 }
 137
 138 static inline void paravirt_free_ldt(struct desc_struct *ldt, unsigned entries)
 139 {
 140 }
 141 #endif  /* CONFIG_PARAVIRT */
 142
 143 #define store_ldt(ldt) asm("sldt %0" : "=m"(ldt))
 144
 145 static inline void native_write_idt_entry(gate_desc *idt, int entry, const gate_desc *gate)
 146 {
 147         memcpy(&idt[entry], gate, sizeof(*gate));
 148 }
 149
 150 static inline void native_write_ldt_entry(struct desc_struct *ldt, int entry, const void *desc)
 151 {
 152         memcpy(&ldt[entry], desc, 8);
 153 }
 154
 155 static inline void
 156 native_write_gdt_entry(struct desc_struct *gdt, int entry, const void *desc, int type)
 157 {
 158         unsigned int size;
 159
 160         switch (type) {
 161         case DESC_TSS:  size = sizeof(tss_desc);        break;
 162         case DESC_LDT:  size = sizeof(ldt_desc);        break;
 163         default:        size = sizeof(*gdt);            break;
 164         }
 165
 166         memcpy(&gdt[entry], desc, size);
 167 }
 168
 169 static inline void set_tssldt_descriptor(void *d, unsigned long addr,
 170                                          unsigned type, unsigned size)
 171 {
 172         struct ldttss_desc *desc = d;
 173
 174         memset(desc, 0, sizeof(*desc));
 175
 176         desc->limit0            = (u16) size;
 177         desc->base0             = (u16) addr;
 178         desc->base1             = (addr >> 16) & 0xFF;
 179         desc->type              = type;
 180         desc->p                 = 1;
 181         desc->limit1            = (size >> 16) & 0xF;
 182         desc->base2             = (addr >> 24) & 0xFF;
 183 #ifdef CONFIG_X86_64
 184         desc->base3             = (u32) (addr >> 32);
 185 #endif
 186 }
 187
 188 static inline void __set_tss_desc(unsigned cpu, unsigned int entry, void *addr)
 189 {
 190         struct desc_struct *d = get_cpu_gdt_rw(cpu);
 191         tss_desc tss;
 192
 193         set_tssldt_descriptor(&tss, (unsigned long)addr, DESC_TSS,
 194                               __KERNEL_TSS_LIMIT);
 195         write_gdt_entry(d, entry, &tss, DESC_TSS);
 196 }
 197
 198 #define set_tss_desc(cpu, addr) __set_tss_desc(cpu, GDT_ENTRY_TSS, addr)
 199
 200 static inline void native_set_ldt(const void *addr, unsigned int entries)
 201 {
 202         if (likely(entries == 0))
 203                 asm volatile("lldt %w0"::"q" (0));
 204         else {
 205                 unsigned cpu = smp_processor_id();
 206                 ldt_desc ldt;
 207
 208                 set_tssldt_descriptor(&ldt, (unsigned long)addr, DESC_LDT,
 209                                       entries * LDT_ENTRY_SIZE - 1);
 210                 write_gdt_entry(get_cpu_gdt_rw(cpu), GDT_ENTRY_LDT,
 211                                 &ldt, DESC_LDT);
 212                 asm volatile("lldt %w0"::"q" (GDT_ENTRY_LDT*8));
 213         }
 214 }
 215
 216 static inline void native_load_gdt(const struct desc_ptr *dtr)
 217 {
 218         asm volatile("lgdt %0"::"m" (*dtr));
 219 }
 220
 221 static inline void native_load_idt(const struct desc_ptr *dtr)
 222 {
 223         asm volatile("lidt %0"::"m" (*dtr));
 224 }
 225
 226 static inline void native_store_gdt(struct desc_ptr *dtr)
 227 {
 228         asm volatile("sgdt %0":"=m" (*dtr));
 229 }
 230
 231 static inline void store_idt(struct desc_ptr *dtr)
 232 {
 233         asm volatile("sidt %0":"=m" (*dtr));
 234 }
 235
 236 /*
 237  * The LTR instruction marks the TSS GDT entry as busy. On 64-bit, the GDT is
 238  * a read-only remapping. To prevent a page fault, the GDT is switched to the
 239  * original writeable version when needed.
 240  */
 241 #ifdef CONFIG_X86_64
 242 static inline void native_load_tr_desc(void)
 243 {
 244         struct desc_ptr gdt;
 245         int cpu = raw_smp_processor_id();
 246         bool restore = 0;
 247         struct desc_struct *fixmap_gdt;
 248
 249         native_store_gdt(&gdt);
 250         fixmap_gdt = get_cpu_gdt_ro(cpu);
 251
 252         /*
 253          * If the current GDT is the read-only fixmap, swap to the original
 254          * writeable version. Swap back at the end.
 255          */
 256         if (gdt.address == (unsigned long)fixmap_gdt) {
 257                 load_direct_gdt(cpu);
 258                 restore = 1;
 259         }
 260         asm volatile("ltr %w0"::"q" (GDT_ENTRY_TSS*8));
 261         if (restore)
 262                 load_fixmap_gdt(cpu);
 263 }
 264 #else
 265 static inline void native_load_tr_desc(void)
 266 {
 267         asm volatile("ltr %w0"::"q" (GDT_ENTRY_TSS*8));
 268 }
 269 #endif
 270
 271 static inline unsigned long native_store_tr(void)
 272 {
 273         unsigned long tr;
 274
 275         asm volatile("str %0":"=r" (tr));
 276
 277         return tr;
 278 }
 279
 280 static inline void native_load_tls(struct thread_struct *t, unsigned int cpu)
 281 {
 282         struct desc_struct *gdt = get_cpu_gdt_rw(cpu);
 283         unsigned int i;
 284
 285         for (i = 0; i < GDT_ENTRY_TLS_ENTRIES; i++)
 286                 gdt[GDT_ENTRY_TLS_MIN + i] = t->tls_array[i];
 287 }
 288
 289 DECLARE_PER_CPU(bool, __tss_limit_invalid);
 290
 291 static inline void force_reload_TR(void)
 292 {
 293         struct desc_struct *d = get_current_gdt_rw();
 294         tss_desc tss;
 295
 296         memcpy(&tss, &d[GDT_ENTRY_TSS], sizeof(tss_desc));
 297
 298         /*
 299          * LTR requires an available TSS, and the TSS is currently
 300          * busy.  Make it be available so that LTR will work.
 301          */
 302         tss.type = DESC_TSS;
 303         write_gdt_entry(d, GDT_ENTRY_TSS, &tss, DESC_TSS);
 304
 305         load_TR_desc();
 306         this_cpu_write(__tss_limit_invalid, false);
 307 }
 308
 309 /*
 310  * Call this if you need the TSS limit to be correct, which should be the case
 311  * if and only if you have TIF_IO_BITMAP set or you're switching to a task
 312  * with TIF_IO_BITMAP set.
 313  */
 314 static inline void refresh_tss_limit(void)
 315 {
 316         DEBUG_LOCKS_WARN_ON(preemptible());
 317
 318         if (unlikely(this_cpu_read(__tss_limit_invalid)))
 319                 force_reload_TR();
 320 }
 321
 322 /*
 323  * If you do something evil that corrupts the cached TSS limit (I'm looking
 324  * at you, VMX exits), call this function.
 325  *
 326  * The optimization here is that the TSS limit only matters for Linux if the
 327  * IO bitmap is in use.  If the TSS limit gets forced to its minimum value,
 328  * everything works except that IO bitmap will be ignored and all CPL 3 IO
 329  * instructions will #GP, which is exactly what we want for normal tasks.
 330  */
 331 static inline void invalidate_tss_limit(void)
 332 {
 333         DEBUG_LOCKS_WARN_ON(preemptible());
 334
 335         if (unlikely(test_thread_flag(TIF_IO_BITMAP)))
 336                 force_reload_TR();
 337         else
 338                 this_cpu_write(__tss_limit_invalid, true);
 339 }
 340
 341 /* This intentionally ignores lm, since 32-bit apps don't have that field. */
 342 #define LDT_empty(info)                                 \
 343         ((info)->base_addr              == 0    &&      \
 344          (info)->limit                  == 0    &&      \
 345          (info)->contents               == 0    &&      \
 346          (info)->read_exec_only         == 1    &&      \
 347          (info)->seg_32bit              == 0    &&      \
 348          (info)->limit_in_pages         == 0    &&      \
 349          (info)->seg_not_present        == 1    &&      \
 350          (info)->useable                == 0)
 351
 352 /* Lots of programs expect an all-zero user_desc to mean "no segment at all". */
 353 static inline bool LDT_zero(const struct user_desc *info)
 354 {
 355         return (info->base_addr         == 0 &&
 356                 info->limit             == 0 &&
 357                 info->contents          == 0 &&
 358                 info->read_exec_only    == 0 &&
 359                 info->seg_32bit         == 0 &&
 360                 info->limit_in_pages    == 0 &&
 361                 info->seg_not_present   == 0 &&
 362                 info->useable           == 0);
 363 }
 364
 365 static inline void clear_LDT(void)
 366 {
 367         set_ldt(NULL, 0);
 368 }
 369
 370 static inline unsigned long get_desc_base(const struct desc_struct *desc)
 371 {
 372         return (unsigned)(desc->base0 | ((desc->base1) << 16) | ((desc->base2) << 24));
 373 }
 374
 375 static inline void set_desc_base(struct desc_struct *desc, unsigned long base)
 376 {
 377         desc->base0 = base & 0xffff;
 378         desc->base1 = (base >> 16) & 0xff;
 379         desc->base2 = (base >> 24) & 0xff;
 380 }
 381
 382 static inline unsigned long get_desc_limit(const struct desc_struct *desc)
 383 {
 384         return desc->limit0 | (desc->limit1 << 16);
 385 }
 386
 387 static inline void set_desc_limit(struct desc_struct *desc, unsigned long limit)
 388 {
 389         desc->limit0 = limit & 0xffff;
 390         desc->limit1 = (limit >> 16) & 0xf;
 391 }
 392
 393 void update_intr_gate(unsigned int n, const void *addr);
 394 void alloc_intr_gate(unsigned int n, const void *addr);
 395
 396 extern unsigned long used_vectors[];
 397
 398 #ifdef CONFIG_X86_64
 399 DECLARE_PER_CPU(u32, debug_idt_ctr);
 400 static inline bool is_debug_idt_enabled(void)
 401 {
 402         if (this_cpu_read(debug_idt_ctr))
 403                 return true;
 404
 405         return false;
 406 }
 407
 408 static inline void load_debug_idt(void)
 409 {
 410         load_idt((const struct desc_ptr *)&debug_idt_descr);
 411 }
 412 #else
 413 static inline bool is_debug_idt_enabled(void)
 414 {
 415         return false;
 416 }
 417
 418 static inline void load_debug_idt(void)
 419 {
 420 }
 421 #endif
 422
 423 /*
 424  * The load_current_idt() must be called with interrupts disabled
 425  * to avoid races. That way the IDT will always be set back to the expected
 426  * descriptor. It's also called when a CPU is being initialized, and
 427  * that doesn't need to disable interrupts, as nothing should be
 428  * bothering the CPU then.
 429  */
 430 static inline void load_current_idt(void)
 431 {
 432         if (is_debug_idt_enabled())
 433                 load_debug_idt();
 434         else
 435                 load_idt((const struct desc_ptr *)&idt_descr);
 436 }
 437
 438 extern void idt_setup_early_handler(void);
 439 extern void idt_setup_early_traps(void);
 440 extern void idt_setup_traps(void);
 441 extern void idt_setup_apic_and_irq_gates(void);
 442
 443 #ifdef CONFIG_X86_64
 444 extern void idt_setup_early_pf(void);
 445 extern void idt_setup_ist_traps(void);
 446 extern void idt_setup_debugidt_traps(void);
 447 #else
 448 static inline void idt_setup_early_pf(void) { }
 449 static inline void idt_setup_ist_traps(void) { }
 450 static inline void idt_setup_debugidt_traps(void) { }
 451 #endif
 452
 453 extern void idt_invalidate(void *addr);
 454
 455 #endif /* _ASM_X86_DESC_H */