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