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/mm.h>
  17 #include <linux/init.h>
  18 #include <linux/sched.h>
  19 #include <linux/seq_file.h>
  20
  21 #include <asm/kasan.h>
  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", "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 <= 3 && pr & _PAGE_PSE)
 166                         pt_dump_cont_printf(m, dmsg, "PSE ");
 167                 else
 168                         pt_dump_cont_printf(m, dmsg, "    ");
 169                 if ((level == 4 && pr & _PAGE_PAT) ||
 170                     ((level == 3 || level == 2) && 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 #ifdef CONFIG_X86_64
 192         return (signed long)(u << 16) >> 16;
 193 #else
 194         return u;
 195 #endif
 196 }
 197
 198 /*
 199  * This function gets called on a break in a continuous series
 200  * of PTE entries; the next one is different so we need to
 201  * print what we collected so far.
 202  */
 203 static void note_page(struct seq_file *m, struct pg_state *st,
 204                       pgprot_t new_prot, int level)
 205 {
 206         pgprotval_t prot, cur;
 207         static const char units[] = "BKMGTPE";
 208
 209         /*
 210          * If we have a "break" in the series, we need to flush the state that
 211          * we have now. "break" is either changing perms, levels or
 212          * address space marker.
 213          */
 214         prot = pgprot_val(new_prot);
 215         cur = pgprot_val(st->current_prot);
 216
 217         if (!st->level) {
 218                 /* First entry */
 219                 st->current_prot = new_prot;
 220                 st->level = level;
 221                 st->marker = address_markers;
 222                 st->lines = 0;
 223                 pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
 224                                    st->marker->name);
 225         } else if (prot != cur || level != st->level ||
 226                    st->current_address >= st->marker[1].start_address) {
 227                 const char *unit = units;
 228                 unsigned long delta;
 229                 int width = sizeof(unsigned long) * 2;
 230                 pgprotval_t pr = pgprot_val(st->current_prot);
 231
 232                 if (st->check_wx && (pr & _PAGE_RW) && !(pr & _PAGE_NX)) {
 233                         WARN_ONCE(1,
 234                                   "x86/mm: Found insecure W+X mapping at address %p/%pS\n",
 235                                   (void *)st->start_address,
 236                                   (void *)st->start_address);
 237                         st->wx_pages += (st->current_address -
 238                                          st->start_address) / PAGE_SIZE;
 239                 }
 240
 241                 /*
 242                  * Now print the actual finished series
 243                  */
 244                 if (!st->marker->max_lines ||
 245                     st->lines < st->marker->max_lines) {
 246                         pt_dump_seq_printf(m, st->to_dmesg,
 247                                            "0x%0*lx-0x%0*lx   ",
 248                                            width, st->start_address,
 249                                            width, st->current_address);
 250
 251                         delta = st->current_address - st->start_address;
 252                         while (!(delta & 1023) && unit[1]) {
 253                                 delta >>= 10;
 254                                 unit++;
 255                         }
 256                         pt_dump_cont_printf(m, st->to_dmesg, "%9lu%c ",
 257                                             delta, *unit);
 258                         printk_prot(m, st->current_prot, st->level,
 259                                     st->to_dmesg);
 260                 }
 261                 st->lines++;
 262
 263                 /*
 264                  * We print markers for special areas of address space,
 265                  * such as the start of vmalloc space etc.
 266                  * This helps in the interpretation.
 267                  */
 268                 if (st->current_address >= st->marker[1].start_address) {
 269                         if (st->marker->max_lines &&
 270                             st->lines > st->marker->max_lines) {
 271                                 unsigned long nskip =
 272                                         st->lines - st->marker->max_lines;
 273                                 pt_dump_seq_printf(m, st->to_dmesg,
 274                                                    "... %lu entr%s skipped ... \n",
 275                                                    nskip,
 276                                                    nskip == 1 ? "y" : "ies");
 277                         }
 278                         st->marker++;
 279                         st->lines = 0;
 280                         pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
 281                                            st->marker->name);
 282                 }
 283
 284                 st->start_address = st->current_address;
 285                 st->current_prot = new_prot;
 286                 st->level = level;
 287         }
 288 }
 289
 290 static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr, unsigned long P)
 291 {
 292         int i;
 293         pte_t *start;
 294         pgprotval_t prot;
 295
 296         start = (pte_t *)pmd_page_vaddr(addr);
 297         for (i = 0; i < PTRS_PER_PTE; i++) {
 298                 prot = pte_flags(*start);
 299                 st->current_address = normalize_addr(P + i * PTE_LEVEL_MULT);
 300                 note_page(m, st, __pgprot(prot), 4);
 301                 start++;
 302         }
 303 }
 304
 305 #if PTRS_PER_PMD > 1
 306
 307 static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr, unsigned long P)
 308 {
 309         int i;
 310         pmd_t *start;
 311         pgprotval_t prot;
 312
 313         start = (pmd_t *)pud_page_vaddr(addr);
 314         for (i = 0; i < PTRS_PER_PMD; i++) {
 315                 st->current_address = normalize_addr(P + i * PMD_LEVEL_MULT);
 316                 if (!pmd_none(*start)) {
 317                         if (pmd_large(*start) || !pmd_present(*start)) {
 318                                 prot = pmd_flags(*start);
 319                                 note_page(m, st, __pgprot(prot), 3);
 320                         } else {
 321                                 walk_pte_level(m, st, *start,
 322                                                P + i * PMD_LEVEL_MULT);
 323                         }
 324                 } else
 325                         note_page(m, st, __pgprot(0), 3);
 326                 start++;
 327         }
 328 }
 329
 330 #else
 331 #define walk_pmd_level(m,s,a,p) walk_pte_level(m,s,__pmd(pud_val(a)),p)
 332 #define pud_large(a) pmd_large(__pmd(pud_val(a)))
 333 #define pud_none(a)  pmd_none(__pmd(pud_val(a)))
 334 #endif
 335
 336 #if PTRS_PER_PUD > 1
 337
 338 /*
 339  * This is an optimization for CONFIG_DEBUG_WX=y + CONFIG_KASAN=y
 340  * KASAN fills page tables with the same values. Since there is no
 341  * point in checking page table more than once we just skip repeated
 342  * entries. This saves us dozens of seconds during boot.
 343  */
 344 static bool pud_already_checked(pud_t *prev_pud, pud_t *pud, bool checkwx)
 345 {
 346         return checkwx && prev_pud && (pud_val(*prev_pud) == pud_val(*pud));
 347 }
 348
 349 static void walk_pud_level(struct seq_file *m, struct pg_state *st, p4d_t addr, unsigned long P)
 350 {
 351         int i;
 352         pud_t *start;
 353         pgprotval_t prot;
 354         pud_t *prev_pud = NULL;
 355
 356         start = (pud_t *)p4d_page_vaddr(addr);
 357
 358         for (i = 0; i < PTRS_PER_PUD; i++) {
 359                 st->current_address = normalize_addr(P + i * PUD_LEVEL_MULT);
 360                 if (!pud_none(*start) &&
 361                     !pud_already_checked(prev_pud, start, st->check_wx)) {
 362                         if (pud_large(*start) || !pud_present(*start)) {
 363                                 prot = pud_flags(*start);
 364                                 note_page(m, st, __pgprot(prot), 2);
 365                         } else {
 366                                 walk_pmd_level(m, st, *start,
 367                                                P + i * PUD_LEVEL_MULT);
 368                         }
 369                 } else
 370                         note_page(m, st, __pgprot(0), 2);
 371
 372                 prev_pud = start;
 373                 start++;
 374         }
 375 }
 376
 377 #else
 378 #define walk_pud_level(m,s,a,p) walk_pmd_level(m,s,__pud(p4d_val(a)),p)
 379 #define p4d_large(a) pud_large(__pud(p4d_val(a)))
 380 #define p4d_none(a)  pud_none(__pud(p4d_val(a)))
 381 #endif
 382
 383 #if PTRS_PER_P4D > 1
 384
 385 static void walk_p4d_level(struct seq_file *m, struct pg_state *st, pgd_t addr, unsigned long P)
 386 {
 387         int i;
 388         p4d_t *start;
 389         pgprotval_t prot;
 390
 391         start = (p4d_t *)pgd_page_vaddr(addr);
 392
 393         for (i = 0; i < PTRS_PER_P4D; i++) {
 394                 st->current_address = normalize_addr(P + i * P4D_LEVEL_MULT);
 395                 if (!p4d_none(*start)) {
 396                         if (p4d_large(*start) || !p4d_present(*start)) {
 397                                 prot = p4d_flags(*start);
 398                                 note_page(m, st, __pgprot(prot), 2);
 399                         } else {
 400                                 walk_pud_level(m, st, *start,
 401                                                P + i * P4D_LEVEL_MULT);
 402                         }
 403                 } else
 404                         note_page(m, st, __pgprot(0), 2);
 405
 406                 start++;
 407         }
 408 }
 409
 410 #else
 411 #define walk_p4d_level(m,s,a,p) walk_pud_level(m,s,__p4d(pgd_val(a)),p)
 412 #define pgd_large(a) p4d_large(__p4d(pgd_val(a)))
 413 #define pgd_none(a)  p4d_none(__p4d(pgd_val(a)))
 414 #endif
 415
 416 static inline bool is_hypervisor_range(int idx)
 417 {
 418 #ifdef CONFIG_X86_64
 419         /*
 420          * ffff800000000000 - ffff87ffffffffff is reserved for
 421          * the hypervisor.
 422          */
 423         return  (idx >= pgd_index(__PAGE_OFFSET) - 16) &&
 424                 (idx <  pgd_index(__PAGE_OFFSET));
 425 #else
 426         return false;
 427 #endif
 428 }
 429
 430 static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 431                                        bool checkwx)
 432 {
 433 #ifdef CONFIG_X86_64
 434         pgd_t *start = (pgd_t *) &init_top_pgt;
 435 #else
 436         pgd_t *start = swapper_pg_dir;
 437 #endif
 438         pgprotval_t prot;
 439         int i;
 440         struct pg_state st = {};
 441
 442         if (pgd) {
 443                 start = pgd;
 444                 st.to_dmesg = true;
 445         }
 446
 447         st.check_wx = checkwx;
 448         if (checkwx)
 449                 st.wx_pages = 0;
 450
 451         for (i = 0; i < PTRS_PER_PGD; i++) {
 452                 st.current_address = normalize_addr(i * PGD_LEVEL_MULT);
 453                 if (!pgd_none(*start) && !is_hypervisor_range(i)) {
 454                         if (pgd_large(*start) || !pgd_present(*start)) {
 455                                 prot = pgd_flags(*start);
 456                                 note_page(m, &st, __pgprot(prot), 1);
 457                         } else {
 458                                 walk_p4d_level(m, &st, *start,
 459                                                i * PGD_LEVEL_MULT);
 460                         }
 461                 } else
 462                         note_page(m, &st, __pgprot(0), 1);
 463
 464                 cond_resched();
 465                 start++;
 466         }
 467
 468         /* Flush out the last page */
 469         st.current_address = normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT);
 470         note_page(m, &st, __pgprot(0), 0);
 471         if (!checkwx)
 472                 return;
 473         if (st.wx_pages)
 474                 pr_info("x86/mm: Checked W+X mappings: FAILED, %lu W+X pages found.\n",
 475                         st.wx_pages);
 476         else
 477                 pr_info("x86/mm: Checked W+X mappings: passed, no W+X pages found.\n");
 478 }
 479
 480 void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd)
 481 {
 482         ptdump_walk_pgd_level_core(m, pgd, false);
 483 }
 484 EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level);
 485
 486 void ptdump_walk_pgd_level_checkwx(void)
 487 {
 488         ptdump_walk_pgd_level_core(NULL, NULL, true);
 489 }
 490
 491 static int __init pt_dump_init(void)
 492 {
 493         /*
 494          * Various markers are not compile-time constants, so assign them
 495          * here.
 496          */
 497 #ifdef CONFIG_X86_64
 498         address_markers[LOW_KERNEL_NR].start_address = PAGE_OFFSET;
 499         address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
 500         address_markers[VMEMMAP_START_NR].start_address = VMEMMAP_START;
 501 #endif
 502 #ifdef CONFIG_X86_32
 503         address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
 504         address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
 505 # ifdef CONFIG_HIGHMEM
 506         address_markers[PKMAP_BASE_NR].start_address = PKMAP_BASE;
 507 # endif
 508         address_markers[FIXADDR_START_NR].start_address = FIXADDR_START;
 509 #endif
 510
 511         return 0;
 512 }
 513 __initcall(pt_dump_init);