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/module.h>
  18 #include <linux/seq_file.h>
  19
  20 #include <asm/pgtable.h>
  21
  22 /*
  23  * The dumper groups pagetable entries of the same type into one, and for
  24  * that it needs to keep some state when walking, and flush this state
  25  * when a "break" in the continuity is found.
  26  */
  27 struct pg_state {
  28         int level;
  29         pgprot_t current_prot;
  30         unsigned long start_address;
  31         unsigned long current_address;
  32         const struct addr_marker *marker;
  33         unsigned long lines;
  34         bool to_dmesg;
  35         bool check_wx;
  36         unsigned long wx_pages;
  37 };
  38
  39 struct addr_marker {
  40         unsigned long start_address;
  41         const char *name;
  42         unsigned long max_lines;
  43 };
  44
  45 /* indices for address_markers; keep sync'd w/ address_markers below */
  46 enum address_markers_idx {
  47         USER_SPACE_NR = 0,
  48 #ifdef CONFIG_X86_64
  49         KERNEL_SPACE_NR,
  50         LOW_KERNEL_NR,
  51         VMALLOC_START_NR,
  52         VMEMMAP_START_NR,
  53 # ifdef CONFIG_X86_ESPFIX64
  54         ESPFIX_START_NR,
  55 # endif
  56         HIGH_KERNEL_NR,
  57         MODULES_VADDR_NR,
  58         MODULES_END_NR,
  59 #else
  60         KERNEL_SPACE_NR,
  61         VMALLOC_START_NR,
  62         VMALLOC_END_NR,
  63 # ifdef CONFIG_HIGHMEM
  64         PKMAP_BASE_NR,
  65 # endif
  66         FIXADDR_START_NR,
  67 #endif
  68 };
  69
  70 /* Address space markers hints */
  71 static struct addr_marker address_markers[] = {
  72         { 0, "User Space" },
  73 #ifdef CONFIG_X86_64
  74         { 0x8000000000000000UL, "Kernel Space" },
  75         { PAGE_OFFSET,          "Low Kernel Mapping" },
  76         { VMALLOC_START,        "vmalloc() Area" },
  77         { VMEMMAP_START,        "Vmemmap" },
  78 # ifdef CONFIG_X86_ESPFIX64
  79         { ESPFIX_BASE_ADDR,     "ESPfix Area", 16 },
  80 # endif
  81 # ifdef CONFIG_EFI
  82         { EFI_VA_END,           "EFI Runtime Services" },
  83 # endif
  84         { __START_KERNEL_map,   "High Kernel Mapping" },
  85         { MODULES_VADDR,        "Modules" },
  86         { MODULES_END,          "End Modules" },
  87 #else
  88         { PAGE_OFFSET,          "Kernel Mapping" },
  89         { 0/* VMALLOC_START */, "vmalloc() Area" },
  90         { 0/*VMALLOC_END*/,     "vmalloc() End" },
  91 # ifdef CONFIG_HIGHMEM
  92         { 0/*PKMAP_BASE*/,      "Persisent kmap() Area" },
  93 # endif
  94         { 0/*FIXADDR_START*/,   "Fixmap Area" },
  95 #endif
  96         { -1, NULL }            /* End of list */
  97 };
  98
  99 /* Multipliers for offsets within the PTEs */
 100 #define PTE_LEVEL_MULT (PAGE_SIZE)
 101 #define PMD_LEVEL_MULT (PTRS_PER_PTE * PTE_LEVEL_MULT)
 102 #define PUD_LEVEL_MULT (PTRS_PER_PMD * PMD_LEVEL_MULT)
 103 #define PGD_LEVEL_MULT (PTRS_PER_PUD * PUD_LEVEL_MULT)
 104
 105 #define pt_dump_seq_printf(m, to_dmesg, fmt, args...)           \
 106 ({                                                              \
 107         if (to_dmesg)                                   \
 108                 printk(KERN_INFO fmt, ##args);                  \
 109         else                                                    \
 110                 if (m)                                          \
 111                         seq_printf(m, fmt, ##args);             \
 112 })
 113
 114 #define pt_dump_cont_printf(m, to_dmesg, fmt, args...)          \
 115 ({                                                              \
 116         if (to_dmesg)                                   \
 117                 printk(KERN_CONT fmt, ##args);                  \
 118         else                                                    \
 119                 if (m)                                          \
 120                         seq_printf(m, fmt, ##args);             \
 121 })
 122
 123 /*
 124  * Print a readable form of a pgprot_t to the seq_file
 125  */
 126 static void printk_prot(struct seq_file *m, pgprot_t prot, int level, bool dmsg)
 127 {
 128         pgprotval_t pr = pgprot_val(prot);
 129         static const char * const level_name[] =
 130                 { "cr3", "pgd", "pud", "pmd", "pte" };
 131
 132         if (!pgprot_val(prot)) {
 133                 /* Not present */
 134                 pt_dump_cont_printf(m, dmsg, "                              ");
 135         } else {
 136                 if (pr & _PAGE_USER)
 137                         pt_dump_cont_printf(m, dmsg, "USR ");
 138                 else
 139                         pt_dump_cont_printf(m, dmsg, "    ");
 140                 if (pr & _PAGE_RW)
 141                         pt_dump_cont_printf(m, dmsg, "RW ");
 142                 else
 143                         pt_dump_cont_printf(m, dmsg, "ro ");
 144                 if (pr & _PAGE_PWT)
 145                         pt_dump_cont_printf(m, dmsg, "PWT ");
 146                 else
 147                         pt_dump_cont_printf(m, dmsg, "    ");
 148                 if (pr & _PAGE_PCD)
 149                         pt_dump_cont_printf(m, dmsg, "PCD ");
 150                 else
 151                         pt_dump_cont_printf(m, dmsg, "    ");
 152
 153                 /* Bit 7 has a different meaning on level 3 vs 4 */
 154                 if (level <= 3 && pr & _PAGE_PSE)
 155                         pt_dump_cont_printf(m, dmsg, "PSE ");
 156                 else
 157                         pt_dump_cont_printf(m, dmsg, "    ");
 158                 if ((level == 4 && pr & _PAGE_PAT) ||
 159                     ((level == 3 || level == 2) && pr & _PAGE_PAT_LARGE))
 160                         pt_dump_cont_printf(m, dmsg, "PAT ");
 161                 else
 162                         pt_dump_cont_printf(m, dmsg, "    ");
 163                 if (pr & _PAGE_GLOBAL)
 164                         pt_dump_cont_printf(m, dmsg, "GLB ");
 165                 else
 166                         pt_dump_cont_printf(m, dmsg, "    ");
 167                 if (pr & _PAGE_NX)
 168                         pt_dump_cont_printf(m, dmsg, "NX ");
 169                 else
 170                         pt_dump_cont_printf(m, dmsg, "x  ");
 171         }
 172         pt_dump_cont_printf(m, dmsg, "%s\n", level_name[level]);
 173 }
 174
 175 /*
 176  * On 64 bits, sign-extend the 48 bit address to 64 bit
 177  */
 178 static unsigned long normalize_addr(unsigned long u)
 179 {
 180 #ifdef CONFIG_X86_64
 181         return (signed long)(u << 16) >> 16;
 182 #else
 183         return u;
 184 #endif
 185 }
 186
 187 /*
 188  * This function gets called on a break in a continuous series
 189  * of PTE entries; the next one is different so we need to
 190  * print what we collected so far.
 191  */
 192 static void note_page(struct seq_file *m, struct pg_state *st,
 193                       pgprot_t new_prot, int level)
 194 {
 195         pgprotval_t prot, cur;
 196         static const char units[] = "BKMGTPE";
 197
 198         /*
 199          * If we have a "break" in the series, we need to flush the state that
 200          * we have now. "break" is either changing perms, levels or
 201          * address space marker.
 202          */
 203         prot = pgprot_val(new_prot);
 204         cur = pgprot_val(st->current_prot);
 205
 206         if (!st->level) {
 207                 /* First entry */
 208                 st->current_prot = new_prot;
 209                 st->level = level;
 210                 st->marker = address_markers;
 211                 st->lines = 0;
 212                 pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
 213                                    st->marker->name);
 214         } else if (prot != cur || level != st->level ||
 215                    st->current_address >= st->marker[1].start_address) {
 216                 const char *unit = units;
 217                 unsigned long delta;
 218                 int width = sizeof(unsigned long) * 2;
 219                 pgprotval_t pr = pgprot_val(st->current_prot);
 220
 221                 if (st->check_wx && (pr & _PAGE_RW) && !(pr & _PAGE_NX)) {
 222                         WARN_ONCE(1,
 223                                   "x86/mm: Found insecure W+X mapping at address %p/%pS\n",
 224                                   (void *)st->start_address,
 225                                   (void *)st->start_address);
 226                         st->wx_pages += (st->current_address -
 227                                          st->start_address) / PAGE_SIZE;
 228                 }
 229
 230                 /*
 231                  * Now print the actual finished series
 232                  */
 233                 if (!st->marker->max_lines ||
 234                     st->lines < st->marker->max_lines) {
 235                         pt_dump_seq_printf(m, st->to_dmesg,
 236                                            "0x%0*lx-0x%0*lx   ",
 237                                            width, st->start_address,
 238                                            width, st->current_address);
 239
 240                         delta = st->current_address - st->start_address;
 241                         while (!(delta & 1023) && unit[1]) {
 242                                 delta >>= 10;
 243                                 unit++;
 244                         }
 245                         pt_dump_cont_printf(m, st->to_dmesg, "%9lu%c ",
 246                                             delta, *unit);
 247                         printk_prot(m, st->current_prot, st->level,
 248                                     st->to_dmesg);
 249                 }
 250                 st->lines++;
 251
 252                 /*
 253                  * We print markers for special areas of address space,
 254                  * such as the start of vmalloc space etc.
 255                  * This helps in the interpretation.
 256                  */
 257                 if (st->current_address >= st->marker[1].start_address) {
 258                         if (st->marker->max_lines &&
 259                             st->lines > st->marker->max_lines) {
 260                                 unsigned long nskip =
 261                                         st->lines - st->marker->max_lines;
 262                                 pt_dump_seq_printf(m, st->to_dmesg,
 263                                                    "... %lu entr%s skipped ... \n",
 264                                                    nskip,
 265                                                    nskip == 1 ? "y" : "ies");
 266                         }
 267                         st->marker++;
 268                         st->lines = 0;
 269                         pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
 270                                            st->marker->name);
 271                 }
 272
 273                 st->start_address = st->current_address;
 274                 st->current_prot = new_prot;
 275                 st->level = level;
 276         }
 277 }
 278
 279 static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr,
 280                                                         unsigned long P)
 281 {
 282         int i;
 283         pte_t *start;
 284         pgprotval_t prot;
 285
 286         start = (pte_t *) pmd_page_vaddr(addr);
 287         for (i = 0; i < PTRS_PER_PTE; i++) {
 288                 prot = pte_flags(*start);
 289                 st->current_address = normalize_addr(P + i * PTE_LEVEL_MULT);
 290                 note_page(m, st, __pgprot(prot), 4);
 291                 start++;
 292         }
 293 }
 294
 295 #if PTRS_PER_PMD > 1
 296
 297 static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr,
 298                                                         unsigned long P)
 299 {
 300         int i;
 301         pmd_t *start;
 302         pgprotval_t prot;
 303
 304         start = (pmd_t *) pud_page_vaddr(addr);
 305         for (i = 0; i < PTRS_PER_PMD; i++) {
 306                 st->current_address = normalize_addr(P + i * PMD_LEVEL_MULT);
 307                 if (!pmd_none(*start)) {
 308                         if (pmd_large(*start) || !pmd_present(*start)) {
 309                                 prot = pmd_flags(*start);
 310                                 note_page(m, st, __pgprot(prot), 3);
 311                         } else {
 312                                 walk_pte_level(m, st, *start,
 313                                                P + i * PMD_LEVEL_MULT);
 314                         }
 315                 } else
 316                         note_page(m, st, __pgprot(0), 3);
 317                 start++;
 318         }
 319 }
 320
 321 #else
 322 #define walk_pmd_level(m,s,a,p) walk_pte_level(m,s,__pmd(pud_val(a)),p)
 323 #define pud_large(a) pmd_large(__pmd(pud_val(a)))
 324 #define pud_none(a)  pmd_none(__pmd(pud_val(a)))
 325 #endif
 326
 327 #if PTRS_PER_PUD > 1
 328
 329 static void walk_pud_level(struct seq_file *m, struct pg_state *st, pgd_t addr,
 330                                                         unsigned long P)
 331 {
 332         int i;
 333         pud_t *start;
 334         pgprotval_t prot;
 335
 336         start = (pud_t *) pgd_page_vaddr(addr);
 337
 338         for (i = 0; i < PTRS_PER_PUD; i++) {
 339                 st->current_address = normalize_addr(P + i * PUD_LEVEL_MULT);
 340                 if (!pud_none(*start)) {
 341                         if (pud_large(*start) || !pud_present(*start)) {
 342                                 prot = pud_flags(*start);
 343                                 note_page(m, st, __pgprot(prot), 2);
 344                         } else {
 345                                 walk_pmd_level(m, st, *start,
 346                                                P + i * PUD_LEVEL_MULT);
 347                         }
 348                 } else
 349                         note_page(m, st, __pgprot(0), 2);
 350
 351                 start++;
 352         }
 353 }
 354
 355 #else
 356 #define walk_pud_level(m,s,a,p) walk_pmd_level(m,s,__pud(pgd_val(a)),p)
 357 #define pgd_large(a) pud_large(__pud(pgd_val(a)))
 358 #define pgd_none(a)  pud_none(__pud(pgd_val(a)))
 359 #endif
 360
 361 static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 362                                        bool checkwx)
 363 {
 364 #ifdef CONFIG_X86_64
 365         pgd_t *start = (pgd_t *) &init_level4_pgt;
 366 #else
 367         pgd_t *start = swapper_pg_dir;
 368 #endif
 369         pgprotval_t prot;
 370         int i;
 371         struct pg_state st = {};
 372
 373         if (pgd) {
 374                 start = pgd;
 375                 st.to_dmesg = true;
 376         }
 377
 378         st.check_wx = checkwx;
 379         if (checkwx)
 380                 st.wx_pages = 0;
 381
 382         for (i = 0; i < PTRS_PER_PGD; i++) {
 383                 st.current_address = normalize_addr(i * PGD_LEVEL_MULT);
 384                 if (!pgd_none(*start)) {
 385                         if (pgd_large(*start) || !pgd_present(*start)) {
 386                                 prot = pgd_flags(*start);
 387                                 note_page(m, &st, __pgprot(prot), 1);
 388                         } else {
 389                                 walk_pud_level(m, &st, *start,
 390                                                i * PGD_LEVEL_MULT);
 391                         }
 392                 } else
 393                         note_page(m, &st, __pgprot(0), 1);
 394
 395                 start++;
 396         }
 397
 398         /* Flush out the last page */
 399         st.current_address = normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT);
 400         note_page(m, &st, __pgprot(0), 0);
 401         if (!checkwx)
 402                 return;
 403         if (st.wx_pages)
 404                 pr_info("x86/mm: Checked W+X mappings: FAILED, %lu W+X pages found.\n",
 405                         st.wx_pages);
 406         else
 407                 pr_info("x86/mm: Checked W+X mappings: passed, no W+X pages found.\n");
 408 }
 409
 410 void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd)
 411 {
 412         ptdump_walk_pgd_level_core(m, pgd, false);
 413 }
 414
 415 void ptdump_walk_pgd_level_checkwx(void)
 416 {
 417         ptdump_walk_pgd_level_core(NULL, NULL, true);
 418 }
 419
 420 #ifdef CONFIG_X86_PTDUMP
 421 static int ptdump_show(struct seq_file *m, void *v)
 422 {
 423         ptdump_walk_pgd_level(m, NULL);
 424         return 0;
 425 }
 426
 427 static int ptdump_open(struct inode *inode, struct file *filp)
 428 {
 429         return single_open(filp, ptdump_show, NULL);
 430 }
 431
 432 static const struct file_operations ptdump_fops = {
 433         .open           = ptdump_open,
 434         .read           = seq_read,
 435         .llseek         = seq_lseek,
 436         .release        = single_release,
 437 };
 438 #endif
 439
 440 static int pt_dump_init(void)
 441 {
 442 #ifdef CONFIG_X86_PTDUMP
 443         struct dentry *pe;
 444 #endif
 445
 446 #ifdef CONFIG_X86_32
 447         /* Not a compile-time constant on x86-32 */
 448         address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
 449         address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
 450 # ifdef CONFIG_HIGHMEM
 451         address_markers[PKMAP_BASE_NR].start_address = PKMAP_BASE;
 452 # endif
 453         address_markers[FIXADDR_START_NR].start_address = FIXADDR_START;
 454 #endif
 455
 456 #ifdef CONFIG_X86_PTDUMP
 457         pe = debugfs_create_file("kernel_page_tables", 0600, NULL, NULL,
 458                                  &ptdump_fops);
 459         if (!pe)
 460                 return -ENOMEM;
 461 #endif
 462
 463         return 0;
 464 }
 465
 466 __initcall(pt_dump_init);
 467 MODULE_LICENSE("GPL");
 468 MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>");
 469 MODULE_DESCRIPTION("Kernel debugging helper that dumps pagetables");