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 PGD_LEVEL_MULT (PTRS_PER_PUD * PUD_LEVEL_MULT)
 114
 115 #define pt_dump_seq_printf(m, to_dmesg, fmt, args...)           \
 116 ({                                                              \
 117         if (to_dmesg)                                   \
 118                 printk(KERN_INFO fmt, ##args);                  \
 119         else                                                    \
 120                 if (m)                                          \
 121                         seq_printf(m, fmt, ##args);             \
 122 })
 123
 124 #define pt_dump_cont_printf(m, to_dmesg, fmt, args...)          \
 125 ({                                                              \
 126         if (to_dmesg)                                   \
 127                 printk(KERN_CONT fmt, ##args);                  \
 128         else                                                    \
 129                 if (m)                                          \
 130                         seq_printf(m, fmt, ##args);             \
 131 })
 132
 133 /*
 134  * Print a readable form of a pgprot_t to the seq_file
 135  */
 136 static void printk_prot(struct seq_file *m, pgprot_t prot, int level, bool dmsg)
 137 {
 138         pgprotval_t pr = pgprot_val(prot);
 139         static const char * const level_name[] =
 140                 { "cr3", "pgd", "pud", "pmd", "pte" };
 141
 142         if (!pgprot_val(prot)) {
 143                 /* Not present */
 144                 pt_dump_cont_printf(m, dmsg, "                              ");
 145         } else {
 146                 if (pr & _PAGE_USER)
 147                         pt_dump_cont_printf(m, dmsg, "USR ");
 148                 else
 149                         pt_dump_cont_printf(m, dmsg, "    ");
 150                 if (pr & _PAGE_RW)
 151                         pt_dump_cont_printf(m, dmsg, "RW ");
 152                 else
 153                         pt_dump_cont_printf(m, dmsg, "ro ");
 154                 if (pr & _PAGE_PWT)
 155                         pt_dump_cont_printf(m, dmsg, "PWT ");
 156                 else
 157                         pt_dump_cont_printf(m, dmsg, "    ");
 158                 if (pr & _PAGE_PCD)
 159                         pt_dump_cont_printf(m, dmsg, "PCD ");
 160                 else
 161                         pt_dump_cont_printf(m, dmsg, "    ");
 162
 163                 /* Bit 7 has a different meaning on level 3 vs 4 */
 164                 if (level <= 3 && pr & _PAGE_PSE)
 165                         pt_dump_cont_printf(m, dmsg, "PSE ");
 166                 else
 167                         pt_dump_cont_printf(m, dmsg, "    ");
 168                 if ((level == 4 && pr & _PAGE_PAT) ||
 169                     ((level == 3 || level == 2) && pr & _PAGE_PAT_LARGE))
 170                         pt_dump_cont_printf(m, dmsg, "PAT ");
 171                 else
 172                         pt_dump_cont_printf(m, dmsg, "    ");
 173                 if (pr & _PAGE_GLOBAL)
 174                         pt_dump_cont_printf(m, dmsg, "GLB ");
 175                 else
 176                         pt_dump_cont_printf(m, dmsg, "    ");
 177                 if (pr & _PAGE_NX)
 178                         pt_dump_cont_printf(m, dmsg, "NX ");
 179                 else
 180                         pt_dump_cont_printf(m, dmsg, "x  ");
 181         }
 182         pt_dump_cont_printf(m, dmsg, "%s\n", level_name[level]);
 183 }
 184
 185 /*
 186  * On 64 bits, sign-extend the 48 bit address to 64 bit
 187  */
 188 static unsigned long normalize_addr(unsigned long u)
 189 {
 190 #ifdef CONFIG_X86_64
 191         return (signed long)(u << 16) >> 16;
 192 #else
 193         return u;
 194 #endif
 195 }
 196
 197 /*
 198  * This function gets called on a break in a continuous series
 199  * of PTE entries; the next one is different so we need to
 200  * print what we collected so far.
 201  */
 202 static void note_page(struct seq_file *m, struct pg_state *st,
 203                       pgprot_t new_prot, int level)
 204 {
 205         pgprotval_t prot, cur;
 206         static const char units[] = "BKMGTPE";
 207
 208         /*
 209          * If we have a "break" in the series, we need to flush the state that
 210          * we have now. "break" is either changing perms, levels or
 211          * address space marker.
 212          */
 213         prot = pgprot_val(new_prot);
 214         cur = pgprot_val(st->current_prot);
 215
 216         if (!st->level) {
 217                 /* First entry */
 218                 st->current_prot = new_prot;
 219                 st->level = level;
 220                 st->marker = address_markers;
 221                 st->lines = 0;
 222                 pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
 223                                    st->marker->name);
 224         } else if (prot != cur || level != st->level ||
 225                    st->current_address >= st->marker[1].start_address) {
 226                 const char *unit = units;
 227                 unsigned long delta;
 228                 int width = sizeof(unsigned long) * 2;
 229                 pgprotval_t pr = pgprot_val(st->current_prot);
 230
 231                 if (st->check_wx && (pr & _PAGE_RW) && !(pr & _PAGE_NX)) {
 232                         WARN_ONCE(1,
 233                                   "x86/mm: Found insecure W+X mapping at address %p/%pS\n",
 234                                   (void *)st->start_address,
 235                                   (void *)st->start_address);
 236                         st->wx_pages += (st->current_address -
 237                                          st->start_address) / PAGE_SIZE;
 238                 }
 239
 240                 /*
 241                  * Now print the actual finished series
 242                  */
 243                 if (!st->marker->max_lines ||
 244                     st->lines < st->marker->max_lines) {
 245                         pt_dump_seq_printf(m, st->to_dmesg,
 246                                            "0x%0*lx-0x%0*lx   ",
 247                                            width, st->start_address,
 248                                            width, st->current_address);
 249
 250                         delta = st->current_address - st->start_address;
 251                         while (!(delta & 1023) && unit[1]) {
 252                                 delta >>= 10;
 253                                 unit++;
 254                         }
 255                         pt_dump_cont_printf(m, st->to_dmesg, "%9lu%c ",
 256                                             delta, *unit);
 257                         printk_prot(m, st->current_prot, st->level,
 258                                     st->to_dmesg);
 259                 }
 260                 st->lines++;
 261
 262                 /*
 263                  * We print markers for special areas of address space,
 264                  * such as the start of vmalloc space etc.
 265                  * This helps in the interpretation.
 266                  */
 267                 if (st->current_address >= st->marker[1].start_address) {
 268                         if (st->marker->max_lines &&
 269                             st->lines > st->marker->max_lines) {
 270                                 unsigned long nskip =
 271                                         st->lines - st->marker->max_lines;
 272                                 pt_dump_seq_printf(m, st->to_dmesg,
 273                                                    "... %lu entr%s skipped ... \n",
 274                                                    nskip,
 275                                                    nskip == 1 ? "y" : "ies");
 276                         }
 277                         st->marker++;
 278                         st->lines = 0;
 279                         pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
 280                                            st->marker->name);
 281                 }
 282
 283                 st->start_address = st->current_address;
 284                 st->current_prot = new_prot;
 285                 st->level = level;
 286         }
 287 }
 288
 289 static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr,
 290                                                         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,
 308                                                         unsigned long P)
 309 {
 310         int i;
 311         pmd_t *start;
 312         pgprotval_t prot;
 313
 314         start = (pmd_t *) pud_page_vaddr(addr);
 315         for (i = 0; i < PTRS_PER_PMD; i++) {
 316                 st->current_address = normalize_addr(P + i * PMD_LEVEL_MULT);
 317                 if (!pmd_none(*start)) {
 318                         if (pmd_large(*start) || !pmd_present(*start)) {
 319                                 prot = pmd_flags(*start);
 320                                 note_page(m, st, __pgprot(prot), 3);
 321                         } else {
 322                                 walk_pte_level(m, st, *start,
 323                                                P + i * PMD_LEVEL_MULT);
 324                         }
 325                 } else
 326                         note_page(m, st, __pgprot(0), 3);
 327                 start++;
 328         }
 329 }
 330
 331 #else
 332 #define walk_pmd_level(m,s,a,p) walk_pte_level(m,s,__pmd(pud_val(a)),p)
 333 #define pud_large(a) pmd_large(__pmd(pud_val(a)))
 334 #define pud_none(a)  pmd_none(__pmd(pud_val(a)))
 335 #endif
 336
 337 #if PTRS_PER_PUD > 1
 338
 339 /*
 340  * This is an optimization for CONFIG_DEBUG_WX=y + CONFIG_KASAN=y
 341  * KASAN fills page tables with the same values. Since there is no
 342  * point in checking page table more than once we just skip repeated
 343  * entries. This saves us dozens of seconds during boot.
 344  */
 345 static bool pud_already_checked(pud_t *prev_pud, pud_t *pud, bool checkwx)
 346 {
 347         return checkwx && prev_pud && (pud_val(*prev_pud) == pud_val(*pud));
 348 }
 349
 350 static void walk_pud_level(struct seq_file *m, struct pg_state *st, pgd_t addr,
 351                                                         unsigned long P)
 352 {
 353         int i;
 354         pud_t *start;
 355         pgprotval_t prot;
 356         pud_t *prev_pud = NULL;
 357
 358         start = (pud_t *) pgd_page_vaddr(addr);
 359
 360         for (i = 0; i < PTRS_PER_PUD; i++) {
 361                 st->current_address = normalize_addr(P + i * PUD_LEVEL_MULT);
 362                 if (!pud_none(*start) &&
 363                     !pud_already_checked(prev_pud, start, st->check_wx)) {
 364                         if (pud_large(*start) || !pud_present(*start)) {
 365                                 prot = pud_flags(*start);
 366                                 note_page(m, st, __pgprot(prot), 2);
 367                         } else {
 368                                 walk_pmd_level(m, st, *start,
 369                                                P + i * PUD_LEVEL_MULT);
 370                         }
 371                 } else
 372                         note_page(m, st, __pgprot(0), 2);
 373
 374                 prev_pud = start;
 375                 start++;
 376         }
 377 }
 378
 379 #else
 380 #define walk_pud_level(m,s,a,p) walk_pmd_level(m,s,__pud(pgd_val(a)),p)
 381 #define pgd_large(a) pud_large(__pud(pgd_val(a)))
 382 #define pgd_none(a)  pud_none(__pud(pgd_val(a)))
 383 #endif
 384
 385 static inline bool is_hypervisor_range(int idx)
 386 {
 387 #ifdef CONFIG_X86_64
 388         /*
 389          * ffff800000000000 - ffff87ffffffffff is reserved for
 390          * the hypervisor.
 391          */
 392         return  (idx >= pgd_index(__PAGE_OFFSET) - 16) &&
 393                 (idx <  pgd_index(__PAGE_OFFSET));
 394 #else
 395         return false;
 396 #endif
 397 }
 398
 399 static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 400                                        bool checkwx)
 401 {
 402 #ifdef CONFIG_X86_64
 403         pgd_t *start = (pgd_t *) &init_level4_pgt;
 404 #else
 405         pgd_t *start = swapper_pg_dir;
 406 #endif
 407         pgprotval_t prot;
 408         int i;
 409         struct pg_state st = {};
 410
 411         if (pgd) {
 412                 start = pgd;
 413                 st.to_dmesg = true;
 414         }
 415
 416         st.check_wx = checkwx;
 417         if (checkwx)
 418                 st.wx_pages = 0;
 419
 420         for (i = 0; i < PTRS_PER_PGD; i++) {
 421                 st.current_address = normalize_addr(i * PGD_LEVEL_MULT);
 422                 if (!pgd_none(*start) && !is_hypervisor_range(i)) {
 423                         if (pgd_large(*start) || !pgd_present(*start)) {
 424                                 prot = pgd_flags(*start);
 425                                 note_page(m, &st, __pgprot(prot), 1);
 426                         } else {
 427                                 walk_pud_level(m, &st, *start,
 428                                                i * PGD_LEVEL_MULT);
 429                         }
 430                 } else
 431                         note_page(m, &st, __pgprot(0), 1);
 432
 433                 cond_resched();
 434                 start++;
 435         }
 436
 437         /* Flush out the last page */
 438         st.current_address = normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT);
 439         note_page(m, &st, __pgprot(0), 0);
 440         if (!checkwx)
 441                 return;
 442         if (st.wx_pages)
 443                 pr_info("x86/mm: Checked W+X mappings: FAILED, %lu W+X pages found.\n",
 444                         st.wx_pages);
 445         else
 446                 pr_info("x86/mm: Checked W+X mappings: passed, no W+X pages found.\n");
 447 }
 448
 449 void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd)
 450 {
 451         ptdump_walk_pgd_level_core(m, pgd, false);
 452 }
 453 EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level);
 454
 455 void ptdump_walk_pgd_level_checkwx(void)
 456 {
 457         ptdump_walk_pgd_level_core(NULL, NULL, true);
 458 }
 459
 460 static int __init pt_dump_init(void)
 461 {
 462         /*
 463          * Various markers are not compile-time constants, so assign them
 464          * here.
 465          */
 466 #ifdef CONFIG_X86_64
 467         address_markers[LOW_KERNEL_NR].start_address = PAGE_OFFSET;
 468         address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
 469         address_markers[VMEMMAP_START_NR].start_address = VMEMMAP_START;
 470 #endif
 471 #ifdef CONFIG_X86_32
 472         address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
 473         address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
 474 # ifdef CONFIG_HIGHMEM
 475         address_markers[PKMAP_BASE_NR].start_address = PKMAP_BASE;
 476 # endif
 477         address_markers[FIXADDR_START_NR].start_address = FIXADDR_START;
 478 #endif
 479
 480         return 0;
 481 }
 482 __initcall(pt_dump_init);