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 /* indices for address_markers; keep sync'd w/ address_markers below */
  48 enum address_markers_idx {
  49         USER_SPACE_NR = 0,
  50 #ifdef CONFIG_X86_64
  51         KERNEL_SPACE_NR,
  52         LOW_KERNEL_NR,
  53         VMALLOC_START_NR,
  54         VMEMMAP_START_NR,
  55 #ifdef CONFIG_KASAN
  56         KASAN_SHADOW_START_NR,
  57         KASAN_SHADOW_END_NR,
  58 #endif
  59 # ifdef CONFIG_X86_ESPFIX64
  60         ESPFIX_START_NR,
  61 # endif
  62         HIGH_KERNEL_NR,
  63         MODULES_VADDR_NR,
  64         MODULES_END_NR,
  65 #else
  66         KERNEL_SPACE_NR,
  67         VMALLOC_START_NR,
  68         VMALLOC_END_NR,
  69 # ifdef CONFIG_HIGHMEM
  70         PKMAP_BASE_NR,
  71 # endif
  72         FIXADDR_START_NR,
  73 #endif
  74 };
  75
  76 /* Address space markers hints */
  77 static struct addr_marker address_markers[] = {
  78         { 0, "User Space" },
  79 #ifdef CONFIG_X86_64
  80         { 0x8000000000000000UL, "Kernel Space" },
  81         { 0/* PAGE_OFFSET */,   "Low Kernel Mapping" },
  82         { 0/* VMALLOC_START */, "vmalloc() Area" },
  83         { 0/* VMEMMAP_START */, "Vmemmap" },
  84 #ifdef CONFIG_KASAN
  85         { KASAN_SHADOW_START,   "KASAN shadow" },
  86         { KASAN_SHADOW_END,     "KASAN shadow end" },
  87 #endif
  88 # ifdef CONFIG_X86_ESPFIX64
  89         { ESPFIX_BASE_ADDR,     "ESPfix Area", 16 },
  90 # endif
  91 # ifdef CONFIG_EFI
  92         { EFI_VA_END,           "EFI Runtime Services" },
  93 # endif
  94         { __START_KERNEL_map,   "High Kernel Mapping" },
  95         { MODULES_VADDR,        "Modules" },
  96         { MODULES_END,          "End Modules" },
  97 #else
  98         { PAGE_OFFSET,          "Kernel Mapping" },
  99         { 0/* VMALLOC_START */, "vmalloc() Area" },
 100         { 0/*VMALLOC_END*/,     "vmalloc() End" },
 101 # ifdef CONFIG_HIGHMEM
 102         { 0/*PKMAP_BASE*/,      "Persistent kmap() Area" },
 103 # endif
 104         { 0/*FIXADDR_START*/,   "Fixmap Area" },
 105 #endif
 106         { -1, NULL }            /* End of list */
 107 };
 108
 109 /* Multipliers for offsets within the PTEs */
 110 #define PTE_LEVEL_MULT (PAGE_SIZE)
 111 #define PMD_LEVEL_MULT (PTRS_PER_PTE * PTE_LEVEL_MULT)
 112 #define PUD_LEVEL_MULT (PTRS_PER_PMD * PMD_LEVEL_MULT)
 113 #define P4D_LEVEL_MULT (PTRS_PER_PUD * PUD_LEVEL_MULT)
 114 #define PGD_LEVEL_MULT (PTRS_PER_P4D * P4D_LEVEL_MULT)
 115
 116 #define pt_dump_seq_printf(m, to_dmesg, fmt, args...)           \
 117 ({                                                              \
 118         if (to_dmesg)                                   \
 119                 printk(KERN_INFO fmt, ##args);                  \
 120         else                                                    \
 121                 if (m)                                          \
 122                         seq_printf(m, fmt, ##args);             \
 123 })
 124
 125 #define pt_dump_cont_printf(m, to_dmesg, fmt, args...)          \
 126 ({                                                              \
 127         if (to_dmesg)                                   \
 128                 printk(KERN_CONT fmt, ##args);                  \
 129         else                                                    \
 130                 if (m)                                          \
 131                         seq_printf(m, fmt, ##args);             \
 132 })
 133
 134 /*
 135  * Print a readable form of a pgprot_t to the seq_file
 136  */
 137 static void printk_prot(struct seq_file *m, pgprot_t prot, int level, bool dmsg)
 138 {
 139         pgprotval_t pr = pgprot_val(prot);
 140         static const char * const level_name[] =
 141                 { "cr3", "pgd", "p4d", "pud", "pmd", "pte" };
 142
 143         if (!pgprot_val(prot)) {
 144                 /* Not present */
 145                 pt_dump_cont_printf(m, dmsg, "                              ");
 146         } else {
 147                 if (pr & _PAGE_USER)
 148                         pt_dump_cont_printf(m, dmsg, "USR ");
 149                 else
 150                         pt_dump_cont_printf(m, dmsg, "    ");
 151                 if (pr & _PAGE_RW)
 152                         pt_dump_cont_printf(m, dmsg, "RW ");
 153                 else
 154                         pt_dump_cont_printf(m, dmsg, "ro ");
 155                 if (pr & _PAGE_PWT)
 156                         pt_dump_cont_printf(m, dmsg, "PWT ");
 157                 else
 158                         pt_dump_cont_printf(m, dmsg, "    ");
 159                 if (pr & _PAGE_PCD)
 160                         pt_dump_cont_printf(m, dmsg, "PCD ");
 161                 else
 162                         pt_dump_cont_printf(m, dmsg, "    ");
 163
 164                 /* Bit 7 has a different meaning on level 3 vs 4 */
 165                 if (level <= 4 && pr & _PAGE_PSE)
 166                         pt_dump_cont_printf(m, dmsg, "PSE ");
 167                 else
 168                         pt_dump_cont_printf(m, dmsg, "    ");
 169                 if ((level == 5 && pr & _PAGE_PAT) ||
 170                     ((level == 4 || level == 3) && pr & _PAGE_PAT_LARGE))
 171                         pt_dump_cont_printf(m, dmsg, "PAT ");
 172                 else
 173                         pt_dump_cont_printf(m, dmsg, "    ");
 174                 if (pr & _PAGE_GLOBAL)
 175                         pt_dump_cont_printf(m, dmsg, "GLB ");
 176                 else
 177                         pt_dump_cont_printf(m, dmsg, "    ");
 178                 if (pr & _PAGE_NX)
 179                         pt_dump_cont_printf(m, dmsg, "NX ");
 180                 else
 181                         pt_dump_cont_printf(m, dmsg, "x  ");
 182         }
 183         pt_dump_cont_printf(m, dmsg, "%s\n", level_name[level]);
 184 }
 185
 186 /*
 187  * On 64 bits, sign-extend the 48 bit address to 64 bit
 188  */
 189 static unsigned long normalize_addr(unsigned long u)
 190 {
 191         int shift;
 192         if (!IS_ENABLED(CONFIG_X86_64))
 193                 return u;
 194
 195         shift = 64 - (__VIRTUAL_MASK_SHIFT + 1);
 196         return (signed long)(u << shift) >> shift;
 197 }
 198
 199 /*
 200  * This function gets called on a break in a continuous series
 201  * of PTE entries; the next one is different so we need to
 202  * print what we collected so far.
 203  */
 204 static void note_page(struct seq_file *m, struct pg_state *st,
 205                       pgprot_t new_prot, int level)
 206 {
 207         pgprotval_t prot, cur;
 208         static const char units[] = "BKMGTPE";
 209
 210         /*
 211          * If we have a "break" in the series, we need to flush the state that
 212          * we have now. "break" is either changing perms, levels or
 213          * address space marker.
 214          */
 215         prot = pgprot_val(new_prot);
 216         cur = pgprot_val(st->current_prot);
 217
 218         if (!st->level) {
 219                 /* First entry */
 220                 st->current_prot = new_prot;
 221                 st->level = level;
 222                 st->marker = address_markers;
 223                 st->lines = 0;
 224                 pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
 225                                    st->marker->name);
 226         } else if (prot != cur || level != st->level ||
 227                    st->current_address >= st->marker[1].start_address) {
 228                 const char *unit = units;
 229                 unsigned long delta;
 230                 int width = sizeof(unsigned long) * 2;
 231                 pgprotval_t pr = pgprot_val(st->current_prot);
 232
 233                 if (st->check_wx && (pr & _PAGE_RW) && !(pr & _PAGE_NX)) {
 234                         WARN_ONCE(1,
 235                                   "x86/mm: Found insecure W+X mapping at address %p/%pS\n",
 236                                   (void *)st->start_address,
 237                                   (void *)st->start_address);
 238                         st->wx_pages += (st->current_address -
 239                                          st->start_address) / PAGE_SIZE;
 240                 }
 241
 242                 /*
 243                  * Now print the actual finished series
 244                  */
 245                 if (!st->marker->max_lines ||
 246                     st->lines < st->marker->max_lines) {
 247                         pt_dump_seq_printf(m, st->to_dmesg,
 248                                            "0x%0*lx-0x%0*lx   ",
 249                                            width, st->start_address,
 250                                            width, st->current_address);
 251
 252                         delta = st->current_address - st->start_address;
 253                         while (!(delta & 1023) && unit[1]) {
 254                                 delta >>= 10;
 255                                 unit++;
 256                         }
 257                         pt_dump_cont_printf(m, st->to_dmesg, "%9lu%c ",
 258                                             delta, *unit);
 259                         printk_prot(m, st->current_prot, st->level,
 260                                     st->to_dmesg);
 261                 }
 262                 st->lines++;
 263
 264                 /*
 265                  * We print markers for special areas of address space,
 266                  * such as the start of vmalloc space etc.
 267                  * This helps in the interpretation.
 268                  */
 269                 if (st->current_address >= st->marker[1].start_address) {
 270                         if (st->marker->max_lines &&
 271                             st->lines > st->marker->max_lines) {
 272                                 unsigned long nskip =
 273                                         st->lines - st->marker->max_lines;
 274                                 pt_dump_seq_printf(m, st->to_dmesg,
 275                                                    "... %lu entr%s skipped ... \n",
 276                                                    nskip,
 277                                                    nskip == 1 ? "y" : "ies");
 278                         }
 279                         st->marker++;
 280                         st->lines = 0;
 281                         pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
 282                                            st->marker->name);
 283                 }
 284
 285                 st->start_address = st->current_address;
 286                 st->current_prot = new_prot;
 287                 st->level = level;
 288         }
 289 }
 290
 291 static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr, unsigned long P)
 292 {
 293         int i;
 294         pte_t *start;
 295         pgprotval_t prot;
 296
 297         start = (pte_t *)pmd_page_vaddr(addr);
 298         for (i = 0; i < PTRS_PER_PTE; i++) {
 299                 prot = pte_flags(*start);
 300                 st->current_address = normalize_addr(P + i * PTE_LEVEL_MULT);
 301                 note_page(m, st, __pgprot(prot), 5);
 302                 start++;
 303         }
 304 }
 305 #ifdef CONFIG_KASAN
 306
 307 /*
 308  * This is an optimization for KASAN=y case. Since all kasan page tables
 309  * eventually point to the kasan_zero_page we could call note_page()
 310  * right away without walking through lower level page tables. This saves
 311  * us dozens of seconds (minutes for 5-level config) while checking for
 312  * W+X mapping or reading kernel_page_tables debugfs file.
 313  */
 314 static inline bool kasan_page_table(struct seq_file *m, struct pg_state *st,
 315                                 void *pt)
 316 {
 317         if (__pa(pt) == __pa(kasan_zero_pmd) ||
 318 #ifdef CONFIG_X86_5LEVEL
 319             __pa(pt) == __pa(kasan_zero_p4d) ||
 320 #endif
 321             __pa(pt) == __pa(kasan_zero_pud)) {
 322                 pgprotval_t prot = pte_flags(kasan_zero_pte[0]);
 323                 note_page(m, st, __pgprot(prot), 5);
 324                 return true;
 325         }
 326         return false;
 327 }
 328 #else
 329 static inline bool kasan_page_table(struct seq_file *m, struct pg_state *st,
 330                                 void *pt)
 331 {
 332         return false;
 333 }
 334 #endif
 335
 336 #if PTRS_PER_PMD > 1
 337
 338 static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr, unsigned long P)
 339 {
 340         int i;
 341         pmd_t *start, *pmd_start;
 342         pgprotval_t prot;
 343
 344         pmd_start = start = (pmd_t *)pud_page_vaddr(addr);
 345         for (i = 0; i < PTRS_PER_PMD; i++) {
 346                 st->current_address = normalize_addr(P + i * PMD_LEVEL_MULT);
 347                 if (!pmd_none(*start)) {
 348                         if (pmd_large(*start) || !pmd_present(*start)) {
 349                                 prot = pmd_flags(*start);
 350                                 note_page(m, st, __pgprot(prot), 4);
 351                         } else if (!kasan_page_table(m, st, pmd_start)) {
 352                                 walk_pte_level(m, st, *start,
 353                                                P + i * PMD_LEVEL_MULT);
 354                         }
 355                 } else
 356                         note_page(m, st, __pgprot(0), 4);
 357                 start++;
 358         }
 359 }
 360
 361 #else
 362 #define walk_pmd_level(m,s,a,p) walk_pte_level(m,s,__pmd(pud_val(a)),p)
 363 #define pud_large(a) pmd_large(__pmd(pud_val(a)))
 364 #define pud_none(a)  pmd_none(__pmd(pud_val(a)))
 365 #endif
 366
 367 #if PTRS_PER_PUD > 1
 368
 369 static void walk_pud_level(struct seq_file *m, struct pg_state *st, p4d_t addr, unsigned long P)
 370 {
 371         int i;
 372         pud_t *start, *pud_start;
 373         pgprotval_t prot;
 374         pud_t *prev_pud = NULL;
 375
 376         pud_start = start = (pud_t *)p4d_page_vaddr(addr);
 377
 378         for (i = 0; i < PTRS_PER_PUD; i++) {
 379                 st->current_address = normalize_addr(P + i * PUD_LEVEL_MULT);
 380                 if (!pud_none(*start)) {
 381                         if (pud_large(*start) || !pud_present(*start)) {
 382                                 prot = pud_flags(*start);
 383                                 note_page(m, st, __pgprot(prot), 3);
 384                         } else if (!kasan_page_table(m, st, pud_start)) {
 385                                 walk_pmd_level(m, st, *start,
 386                                                P + i * PUD_LEVEL_MULT);
 387                         }
 388                 } else
 389                         note_page(m, st, __pgprot(0), 3);
 390
 391                 prev_pud = start;
 392                 start++;
 393         }
 394 }
 395
 396 #else
 397 #define walk_pud_level(m,s,a,p) walk_pmd_level(m,s,__pud(p4d_val(a)),p)
 398 #define p4d_large(a) pud_large(__pud(p4d_val(a)))
 399 #define p4d_none(a)  pud_none(__pud(p4d_val(a)))
 400 #endif
 401
 402 #if PTRS_PER_P4D > 1
 403
 404 static void walk_p4d_level(struct seq_file *m, struct pg_state *st, pgd_t addr, unsigned long P)
 405 {
 406         int i;
 407         p4d_t *start, *p4d_start;
 408         pgprotval_t prot;
 409
 410         p4d_start = start = (p4d_t *)pgd_page_vaddr(addr);
 411
 412         for (i = 0; i < PTRS_PER_P4D; i++) {
 413                 st->current_address = normalize_addr(P + i * P4D_LEVEL_MULT);
 414                 if (!p4d_none(*start)) {
 415                         if (p4d_large(*start) || !p4d_present(*start)) {
 416                                 prot = p4d_flags(*start);
 417                                 note_page(m, st, __pgprot(prot), 2);
 418                         } else if (!kasan_page_table(m, st, p4d_start)) {
 419                                 walk_pud_level(m, st, *start,
 420                                                P + i * P4D_LEVEL_MULT);
 421                         }
 422                 } else
 423                         note_page(m, st, __pgprot(0), 2);
 424
 425                 start++;
 426         }
 427 }
 428
 429 #else
 430 #define walk_p4d_level(m,s,a,p) walk_pud_level(m,s,__p4d(pgd_val(a)),p)
 431 #define pgd_large(a) p4d_large(__p4d(pgd_val(a)))
 432 #define pgd_none(a)  p4d_none(__p4d(pgd_val(a)))
 433 #endif
 434
 435 static inline bool is_hypervisor_range(int idx)
 436 {
 437 #ifdef CONFIG_X86_64
 438         /*
 439          * ffff800000000000 - ffff87ffffffffff is reserved for
 440          * the hypervisor.
 441          */
 442         return  (idx >= pgd_index(__PAGE_OFFSET) - 16) &&
 443                 (idx <  pgd_index(__PAGE_OFFSET));
 444 #else
 445         return false;
 446 #endif
 447 }
 448
 449 static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 450                                        bool checkwx)
 451 {
 452 #ifdef CONFIG_X86_64
 453         pgd_t *start = (pgd_t *) &init_top_pgt;
 454 #else
 455         pgd_t *start = swapper_pg_dir;
 456 #endif
 457         pgprotval_t prot;
 458         int i;
 459         struct pg_state st = {};
 460
 461         if (pgd) {
 462                 start = pgd;
 463                 st.to_dmesg = true;
 464         }
 465
 466         st.check_wx = checkwx;
 467         if (checkwx)
 468                 st.wx_pages = 0;
 469
 470         for (i = 0; i < PTRS_PER_PGD; i++) {
 471                 st.current_address = normalize_addr(i * PGD_LEVEL_MULT);
 472                 if (!pgd_none(*start) && !is_hypervisor_range(i)) {
 473                         if (pgd_large(*start) || !pgd_present(*start)) {
 474                                 prot = pgd_flags(*start);
 475                                 note_page(m, &st, __pgprot(prot), 1);
 476                         } else {
 477                                 walk_p4d_level(m, &st, *start,
 478                                                i * PGD_LEVEL_MULT);
 479                         }
 480                 } else
 481                         note_page(m, &st, __pgprot(0), 1);
 482
 483                 cond_resched();
 484                 start++;
 485         }
 486
 487         /* Flush out the last page */
 488         st.current_address = normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT);
 489         note_page(m, &st, __pgprot(0), 0);
 490         if (!checkwx)
 491                 return;
 492         if (st.wx_pages)
 493                 pr_info("x86/mm: Checked W+X mappings: FAILED, %lu W+X pages found.\n",
 494                         st.wx_pages);
 495         else
 496                 pr_info("x86/mm: Checked W+X mappings: passed, no W+X pages found.\n");
 497 }
 498
 499 void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd)
 500 {
 501         ptdump_walk_pgd_level_core(m, pgd, false);
 502 }
 503 EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level);
 504
 505 void ptdump_walk_pgd_level_checkwx(void)
 506 {
 507         ptdump_walk_pgd_level_core(NULL, NULL, true);
 508 }
 509
 510 static int __init pt_dump_init(void)
 511 {
 512         /*
 513          * Various markers are not compile-time constants, so assign them
 514          * here.
 515          */
 516 #ifdef CONFIG_X86_64
 517         address_markers[LOW_KERNEL_NR].start_address = PAGE_OFFSET;
 518         address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
 519         address_markers[VMEMMAP_START_NR].start_address = VMEMMAP_START;
 520 #endif
 521 #ifdef CONFIG_X86_32
 522         address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
 523         address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
 524 # ifdef CONFIG_HIGHMEM
 525         address_markers[PKMAP_BASE_NR].start_address = PKMAP_BASE;
 526 # endif
 527         address_markers[FIXADDR_START_NR].start_address = FIXADDR_START;
 528 #endif
 529
 530         return 0;
 531 }
 532 __initcall(pt_dump_init);