arch/x86/mm/dump_pagetables.c

   1 /*
   2  * Debug helper to dump the current kernel pagetables of the system
   3  * so that we can see what the various memory ranges are set to.
   4  *
   5  * (C) Copyright 2008 Intel Corporation
   6  *
   7  * Author: Arjan van de Ven <arjan@linux.intel.com>
   8  *
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU General Public License
  11  * as published by the Free Software Foundation; version 2
  12  * of the License.
  13  */
  14
  15 #include <linux/debugfs.h>
  16 #include <linux/kasan.h>
  17 #include <linux/mm.h>
  18 #include <linux/init.h>
  19 #include <linux/sched.h>
  20 #include <linux/seq_file.h>
  21
  22 #include <asm/pgtable.h>
  23
  24 /*
  25  * The dumper groups pagetable entries of the same type into one, and for
  26  * that it needs to keep some state when walking, and flush this state
  27  * when a "break" in the continuity is found.
  28  */
  29 struct pg_state {
  30         int level;
  31         pgprot_t current_prot;
  32         unsigned long start_address;
  33         unsigned long current_address;
  34         const struct addr_marker *marker;
  35         unsigned long lines;
  36         bool to_dmesg;
  37         bool check_wx;
  38         unsigned long wx_pages;
  39 };
  40
  41 struct addr_marker {
  42         unsigned long start_address;
  43         const char *name;
  44         unsigned long max_lines;
  45 };
  46
  47 /* Address space markers hints */
  48
  49 #ifdef CONFIG_X86_64
  50
  51 enum address_markers_idx {
  52         USER_SPACE_NR = 0,
  53         KERNEL_SPACE_NR,
  54         LOW_KERNEL_NR,
  55         VMALLOC_START_NR,
  56         VMEMMAP_START_NR,
  57 #ifdef CONFIG_KASAN
  58         KASAN_SHADOW_START_NR,
  59         KASAN_SHADOW_END_NR,
  60 #endif
  61         CPU_ENTRY_AREA_NR,
  62 #ifdef CONFIG_X86_ESPFIX64
  63         ESPFIX_START_NR,
  64 #endif
  65 #ifdef CONFIG_EFI
  66         EFI_END_NR,
  67 #endif
  68         HIGH_KERNEL_NR,
  69         MODULES_VADDR_NR,
  70         MODULES_END_NR,
  71         FIXADDR_START_NR,
  72         END_OF_SPACE_NR,
  73 };
  74
  75 static struct addr_marker address_markers[] = {
  76         [USER_SPACE_NR]         = { 0,                  "User Space" },
  77         [KERNEL_SPACE_NR]       = { (1UL << 63),        "Kernel Space" },
  78         [LOW_KERNEL_NR]         = { 0UL,                "Low Kernel Mapping" },
  79         [VMALLOC_START_NR]      = { 0UL,                "vmalloc() Area" },
  80         [VMEMMAP_START_NR]      = { 0UL,                "Vmemmap" },
  81 #ifdef CONFIG_KASAN
  82         [KASAN_SHADOW_START_NR] = { KASAN_SHADOW_START, "KASAN shadow" },
  83         [KASAN_SHADOW_END_NR]   = { KASAN_SHADOW_END,   "KASAN shadow end" },
  84 #endif
  85         [CPU_ENTRY_AREA_NR]     = { CPU_ENTRY_AREA_BASE,"CPU entry Area" },
  86 #ifdef CONFIG_X86_ESPFIX64
  87         [ESPFIX_START_NR]       = { ESPFIX_BASE_ADDR,   "ESPfix Area", 16 },
  88 #endif
  89 #ifdef CONFIG_EFI
  90         [EFI_END_NR]            = { EFI_VA_END,         "EFI Runtime Services" },
  91 #endif
  92         [HIGH_KERNEL_NR]        = { __START_KERNEL_map, "High Kernel Mapping" },
  93         [MODULES_VADDR_NR]      = { MODULES_VADDR,      "Modules" },
  94         [MODULES_END_NR]        = { MODULES_END,        "End Modules" },
  95         [FIXADDR_START_NR]      = { FIXADDR_START,      "Fixmap Area" },
  96         [END_OF_SPACE_NR]       = { -1,                 NULL }
  97 };
  98
  99 #else /* CONFIG_X86_64 */
 100
 101 enum address_markers_idx {
 102         USER_SPACE_NR = 0,
 103         KERNEL_SPACE_NR,
 104         VMALLOC_START_NR,
 105         VMALLOC_END_NR,
 106 #ifdef CONFIG_HIGHMEM
 107         PKMAP_BASE_NR,
 108 #endif
 109         CPU_ENTRY_AREA_NR,
 110         FIXADDR_START_NR,
 111         END_OF_SPACE_NR,
 112 };
 113
 114 static struct addr_marker address_markers[] = {
 115         [USER_SPACE_NR]         = { 0,                  "User Space" },
 116         [KERNEL_SPACE_NR]       = { PAGE_OFFSET,        "Kernel Mapping" },
 117         [VMALLOC_START_NR]      = { 0UL,                "vmalloc() Area" },
 118         [VMALLOC_END_NR]        = { 0UL,                "vmalloc() End" },
 119 #ifdef CONFIG_HIGHMEM
 120         [PKMAP_BASE_NR]         = { 0UL,                "Persistent kmap() Area" },
 121 #endif
 122         [CPU_ENTRY_AREA_NR]     = { 0UL,                "CPU entry area" },
 123         [FIXADDR_START_NR]      = { 0UL,                "Fixmap area" },
 124         [END_OF_SPACE_NR]       = { -1,                 NULL }
 125 };
 126
 127 #endif /* !CONFIG_X86_64 */
 128
 129 /* Multipliers for offsets within the PTEs */
 130 #define PTE_LEVEL_MULT (PAGE_SIZE)
 131 #define PMD_LEVEL_MULT (PTRS_PER_PTE * PTE_LEVEL_MULT)
 132 #define PUD_LEVEL_MULT (PTRS_PER_PMD * PMD_LEVEL_MULT)
 133 #define P4D_LEVEL_MULT (PTRS_PER_PUD * PUD_LEVEL_MULT)
 134 #define PGD_LEVEL_MULT (PTRS_PER_P4D * P4D_LEVEL_MULT)
 135
 136 #define pt_dump_seq_printf(m, to_dmesg, fmt, args...)           \
 137 ({                                                              \
 138         if (to_dmesg)                                   \
 139                 printk(KERN_INFO fmt, ##args);                  \
 140         else                                                    \
 141                 if (m)                                          \
 142                         seq_printf(m, fmt, ##args);             \
 143 })
 144
 145 #define pt_dump_cont_printf(m, to_dmesg, fmt, args...)          \
 146 ({                                                              \
 147         if (to_dmesg)                                   \
 148                 printk(KERN_CONT fmt, ##args);                  \
 149         else                                                    \
 150                 if (m)                                          \
 151                         seq_printf(m, fmt, ##args);             \
 152 })
 153
 154 /*
 155  * Print a readable form of a pgprot_t to the seq_file
 156  */
 157 static void printk_prot(struct seq_file *m, pgprot_t prot, int level, bool dmsg)
 158 {
 159         pgprotval_t pr = pgprot_val(prot);
 160         static const char * const level_name[] =
 161                 { "cr3", "pgd", "p4d", "pud", "pmd", "pte" };
 162
 163         if (!(pr & _PAGE_PRESENT)) {
 164                 /* Not present */
 165                 pt_dump_cont_printf(m, dmsg, "                              ");
 166         } else {
 167                 if (pr & _PAGE_USER)
 168                         pt_dump_cont_printf(m, dmsg, "USR ");
 169                 else
 170                         pt_dump_cont_printf(m, dmsg, "    ");
 171                 if (pr & _PAGE_RW)
 172                         pt_dump_cont_printf(m, dmsg, "RW ");
 173                 else
 174                         pt_dump_cont_printf(m, dmsg, "ro ");
 175                 if (pr & _PAGE_PWT)
 176                         pt_dump_cont_printf(m, dmsg, "PWT ");
 177                 else
 178                         pt_dump_cont_printf(m, dmsg, "    ");
 179                 if (pr & _PAGE_PCD)
 180                         pt_dump_cont_printf(m, dmsg, "PCD ");
 181                 else
 182                         pt_dump_cont_printf(m, dmsg, "    ");
 183
 184                 /* Bit 7 has a different meaning on level 3 vs 4 */
 185                 if (level <= 4 && pr & _PAGE_PSE)
 186                         pt_dump_cont_printf(m, dmsg, "PSE ");
 187                 else
 188                         pt_dump_cont_printf(m, dmsg, "    ");
 189                 if ((level == 5 && pr & _PAGE_PAT) ||
 190                     ((level == 4 || level == 3) && pr & _PAGE_PAT_LARGE))
 191                         pt_dump_cont_printf(m, dmsg, "PAT ");
 192                 else
 193                         pt_dump_cont_printf(m, dmsg, "    ");
 194                 if (pr & _PAGE_GLOBAL)
 195                         pt_dump_cont_printf(m, dmsg, "GLB ");
 196                 else
 197                         pt_dump_cont_printf(m, dmsg, "    ");
 198                 if (pr & _PAGE_NX)
 199                         pt_dump_cont_printf(m, dmsg, "NX ");
 200                 else
 201                         pt_dump_cont_printf(m, dmsg, "x  ");
 202         }
 203         pt_dump_cont_printf(m, dmsg, "%s\n", level_name[level]);
 204 }
 205
 206 /*
 207  * On 64 bits, sign-extend the 48 bit address to 64 bit
 208  */
 209 static unsigned long normalize_addr(unsigned long u)
 210 {
 211         int shift;
 212         if (!IS_ENABLED(CONFIG_X86_64))
 213                 return u;
 214
 215         shift = 64 - (__VIRTUAL_MASK_SHIFT + 1);
 216         return (signed long)(u << shift) >> shift;
 217 }
 218
 219 /*
 220  * This function gets called on a break in a continuous series
 221  * of PTE entries; the next one is different so we need to
 222  * print what we collected so far.
 223  */
 224 static void note_page(struct seq_file *m, struct pg_state *st,
 225                       pgprot_t new_prot, int level)
 226 {
 227         pgprotval_t prot, cur;
 228         static const char units[] = "BKMGTPE";
 229
 230         /*
 231          * If we have a "break" in the series, we need to flush the state that
 232          * we have now. "break" is either changing perms, levels or
 233          * address space marker.
 234          */
 235         prot = pgprot_val(new_prot);
 236         cur = pgprot_val(st->current_prot);
 237
 238         if (!st->level) {
 239                 /* First entry */
 240                 st->current_prot = new_prot;
 241                 st->level = level;
 242                 st->marker = address_markers;
 243                 st->lines = 0;
 244                 pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
 245                                    st->marker->name);
 246         } else if (prot != cur || level != st->level ||
 247                    st->current_address >= st->marker[1].start_address) {
 248                 const char *unit = units;
 249                 unsigned long delta;
 250                 int width = sizeof(unsigned long) * 2;
 251                 pgprotval_t pr = pgprot_val(st->current_prot);
 252
 253                 if (st->check_wx && (pr & _PAGE_RW) && !(pr & _PAGE_NX)) {
 254                         WARN_ONCE(1,
 255                                   "x86/mm: Found insecure W+X mapping at address %p/%pS\n",
 256                                   (void *)st->start_address,
 257                                   (void *)st->start_address);
 258                         st->wx_pages += (st->current_address -
 259                                          st->start_address) / PAGE_SIZE;
 260                 }
 261
 262                 /*
 263                  * Now print the actual finished series
 264                  */
 265                 if (!st->marker->max_lines ||
 266                     st->lines < st->marker->max_lines) {
 267                         pt_dump_seq_printf(m, st->to_dmesg,
 268                                            "0x%0*lx-0x%0*lx   ",
 269                                            width, st->start_address,
 270                                            width, st->current_address);
 271
 272                         delta = st->current_address - st->start_address;
 273                         while (!(delta & 1023) && unit[1]) {
 274                                 delta >>= 10;
 275                                 unit++;
 276                         }
 277                         pt_dump_cont_printf(m, st->to_dmesg, "%9lu%c ",
 278                                             delta, *unit);
 279                         printk_prot(m, st->current_prot, st->level,
 280                                     st->to_dmesg);
 281                 }
 282                 st->lines++;
 283
 284                 /*
 285                  * We print markers for special areas of address space,
 286                  * such as the start of vmalloc space etc.
 287                  * This helps in the interpretation.
 288                  */
 289                 if (st->current_address >= st->marker[1].start_address) {
 290                         if (st->marker->max_lines &&
 291                             st->lines > st->marker->max_lines) {
 292                                 unsigned long nskip =
 293                                         st->lines - st->marker->max_lines;
 294                                 pt_dump_seq_printf(m, st->to_dmesg,
 295                                                    "... %lu entr%s skipped ... \n",
 296                                                    nskip,
 297                                                    nskip == 1 ? "y" : "ies");
 298                         }
 299                         st->marker++;
 300                         st->lines = 0;
 301                         pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
 302                                            st->marker->name);
 303                 }
 304
 305                 st->start_address = st->current_address;
 306                 st->current_prot = new_prot;
 307                 st->level = level;
 308         }
 309 }
 310
 311 static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr, unsigned long P)
 312 {
 313         int i;
 314         pte_t *start;
 315         pgprotval_t prot;
 316
 317         start = (pte_t *)pmd_page_vaddr(addr);
 318         for (i = 0; i < PTRS_PER_PTE; i++) {
 319                 prot = pte_flags(*start);
 320                 st->current_address = normalize_addr(P + i * PTE_LEVEL_MULT);
 321                 note_page(m, st, __pgprot(prot), 5);
 322                 start++;
 323         }
 324 }
 325 #ifdef CONFIG_KASAN
 326
 327 /*
 328  * This is an optimization for KASAN=y case. Since all kasan page tables
 329  * eventually point to the kasan_zero_page we could call note_page()
 330  * right away without walking through lower level page tables. This saves
 331  * us dozens of seconds (minutes for 5-level config) while checking for
 332  * W+X mapping or reading kernel_page_tables debugfs file.
 333  */
 334 static inline bool kasan_page_table(struct seq_file *m, struct pg_state *st,
 335                                 void *pt)
 336 {
 337         if (__pa(pt) == __pa(kasan_zero_pmd) ||
 338 #ifdef CONFIG_X86_5LEVEL
 339             __pa(pt) == __pa(kasan_zero_p4d) ||
 340 #endif
 341             __pa(pt) == __pa(kasan_zero_pud)) {
 342                 pgprotval_t prot = pte_flags(kasan_zero_pte[0]);
 343                 note_page(m, st, __pgprot(prot), 5);
 344                 return true;
 345         }
 346         return false;
 347 }
 348 #else
 349 static inline bool kasan_page_table(struct seq_file *m, struct pg_state *st,
 350                                 void *pt)
 351 {
 352         return false;
 353 }
 354 #endif
 355
 356 #if PTRS_PER_PMD > 1
 357
 358 static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr, unsigned long P)
 359 {
 360         int i;
 361         pmd_t *start, *pmd_start;
 362         pgprotval_t prot;
 363
 364         pmd_start = start = (pmd_t *)pud_page_vaddr(addr);
 365         for (i = 0; i < PTRS_PER_PMD; i++) {
 366                 st->current_address = normalize_addr(P + i * PMD_LEVEL_MULT);
 367                 if (!pmd_none(*start)) {
 368                         if (pmd_large(*start) || !pmd_present(*start)) {
 369                                 prot = pmd_flags(*start);
 370                                 note_page(m, st, __pgprot(prot), 4);
 371                         } else if (!kasan_page_table(m, st, pmd_start)) {
 372                                 walk_pte_level(m, st, *start,
 373                                                P + i * PMD_LEVEL_MULT);
 374                         }
 375                 } else
 376                         note_page(m, st, __pgprot(0), 4);
 377                 start++;
 378         }
 379 }
 380
 381 #else
 382 #define walk_pmd_level(m,s,a,p) walk_pte_level(m,s,__pmd(pud_val(a)),p)
 383 #define pud_large(a) pmd_large(__pmd(pud_val(a)))
 384 #define pud_none(a)  pmd_none(__pmd(pud_val(a)))
 385 #endif
 386
 387 #if PTRS_PER_PUD > 1
 388
 389 static void walk_pud_level(struct seq_file *m, struct pg_state *st, p4d_t addr, unsigned long P)
 390 {
 391         int i;
 392         pud_t *start, *pud_start;
 393         pgprotval_t prot;
 394         pud_t *prev_pud = NULL;
 395
 396         pud_start = start = (pud_t *)p4d_page_vaddr(addr);
 397
 398         for (i = 0; i < PTRS_PER_PUD; i++) {
 399                 st->current_address = normalize_addr(P + i * PUD_LEVEL_MULT);
 400                 if (!pud_none(*start)) {
 401                         if (pud_large(*start) || !pud_present(*start)) {
 402                                 prot = pud_flags(*start);
 403                                 note_page(m, st, __pgprot(prot), 3);
 404                         } else if (!kasan_page_table(m, st, pud_start)) {
 405                                 walk_pmd_level(m, st, *start,
 406                                                P + i * PUD_LEVEL_MULT);
 407                         }
 408                 } else
 409                         note_page(m, st, __pgprot(0), 3);
 410
 411                 prev_pud = start;
 412                 start++;
 413         }
 414 }
 415
 416 #else
 417 #define walk_pud_level(m,s,a,p) walk_pmd_level(m,s,__pud(p4d_val(a)),p)
 418 #define p4d_large(a) pud_large(__pud(p4d_val(a)))
 419 #define p4d_none(a)  pud_none(__pud(p4d_val(a)))
 420 #endif
 421
 422 #if PTRS_PER_P4D > 1
 423
 424 static void walk_p4d_level(struct seq_file *m, struct pg_state *st, pgd_t addr, unsigned long P)
 425 {
 426         int i;
 427         p4d_t *start, *p4d_start;
 428         pgprotval_t prot;
 429
 430         p4d_start = start = (p4d_t *)pgd_page_vaddr(addr);
 431
 432         for (i = 0; i < PTRS_PER_P4D; i++) {
 433                 st->current_address = normalize_addr(P + i * P4D_LEVEL_MULT);
 434                 if (!p4d_none(*start)) {
 435                         if (p4d_large(*start) || !p4d_present(*start)) {
 436                                 prot = p4d_flags(*start);
 437                                 note_page(m, st, __pgprot(prot), 2);
 438                         } else if (!kasan_page_table(m, st, p4d_start)) {
 439                                 walk_pud_level(m, st, *start,
 440                                                P + i * P4D_LEVEL_MULT);
 441                         }
 442                 } else
 443                         note_page(m, st, __pgprot(0), 2);
 444
 445                 start++;
 446         }
 447 }
 448
 449 #else
 450 #define walk_p4d_level(m,s,a,p) walk_pud_level(m,s,__p4d(pgd_val(a)),p)
 451 #define pgd_large(a) p4d_large(__p4d(pgd_val(a)))
 452 #define pgd_none(a)  p4d_none(__p4d(pgd_val(a)))
 453 #endif
 454
 455 static inline bool is_hypervisor_range(int idx)
 456 {
 457 #ifdef CONFIG_X86_64
 458         /*
 459          * ffff800000000000 - ffff87ffffffffff is reserved for
 460          * the hypervisor.
 461          */
 462         return  (idx >= pgd_index(__PAGE_OFFSET) - 16) &&
 463                 (idx <  pgd_index(__PAGE_OFFSET));
 464 #else
 465         return false;
 466 #endif
 467 }
 468
 469 static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 470                                        bool checkwx)
 471 {
 472 #ifdef CONFIG_X86_64
 473         pgd_t *start = (pgd_t *) &init_top_pgt;
 474 #else
 475         pgd_t *start = swapper_pg_dir;
 476 #endif
 477         pgprotval_t prot;
 478         int i;
 479         struct pg_state st = {};
 480
 481         if (pgd) {
 482                 start = pgd;
 483                 st.to_dmesg = true;
 484         }
 485
 486         st.check_wx = checkwx;
 487         if (checkwx)
 488                 st.wx_pages = 0;
 489
 490         for (i = 0; i < PTRS_PER_PGD; i++) {
 491                 st.current_address = normalize_addr(i * PGD_LEVEL_MULT);
 492                 if (!pgd_none(*start) && !is_hypervisor_range(i)) {
 493                         if (pgd_large(*start) || !pgd_present(*start)) {
 494                                 prot = pgd_flags(*start);
 495                                 note_page(m, &st, __pgprot(prot), 1);
 496                         } else {
 497                                 walk_p4d_level(m, &st, *start,
 498                                                i * PGD_LEVEL_MULT);
 499                         }
 500                 } else
 501                         note_page(m, &st, __pgprot(0), 1);
 502
 503                 cond_resched();
 504                 start++;
 505         }
 506
 507         /* Flush out the last page */
 508         st.current_address = normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT);
 509         note_page(m, &st, __pgprot(0), 0);
 510         if (!checkwx)
 511                 return;
 512         if (st.wx_pages)
 513                 pr_info("x86/mm: Checked W+X mappings: FAILED, %lu W+X pages found.\n",
 514                         st.wx_pages);
 515         else
 516                 pr_info("x86/mm: Checked W+X mappings: passed, no W+X pages found.\n");
 517 }
 518
 519 void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd)
 520 {
 521         ptdump_walk_pgd_level_core(m, pgd, false);
 522 }
 523 EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level);
 524
 525 void ptdump_walk_pgd_level_checkwx(void)
 526 {
 527         ptdump_walk_pgd_level_core(NULL, NULL, true);
 528 }
 529
 530 static int __init pt_dump_init(void)
 531 {
 532         /*
 533          * Various markers are not compile-time constants, so assign them
 534          * here.
 535          */
 536 #ifdef CONFIG_X86_64
 537         address_markers[LOW_KERNEL_NR].start_address = PAGE_OFFSET;
 538         address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
 539         address_markers[VMEMMAP_START_NR].start_address = VMEMMAP_START;
 540 #endif
 541 #ifdef CONFIG_X86_32
 542         address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
 543         address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
 544 # ifdef CONFIG_HIGHMEM
 545         address_markers[PKMAP_BASE_NR].start_address = PKMAP_BASE;
 546 # endif
 547         address_markers[FIXADDR_START_NR].start_address = FIXADDR_START;
 548         address_markers[CPU_ENTRY_AREA_NR].start_address = CPU_ENTRY_AREA_BASE;
 549 #endif
 550         return 0;
 551 }
 552 __initcall(pt_dump_init);