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