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 };
  34
  35 struct addr_marker {
  36         unsigned long start_address;
  37         const char *name;
  38 };
  39
  40 /* Address space markers hints */
  41 static struct addr_marker address_markers[] = {
  42         { 0, "User Space" },
  43 #ifdef CONFIG_X86_64
  44         { 0x8000000000000000UL, "Kernel Space" },
  45         { PAGE_OFFSET,          "Low Kernel Mapping" },
  46         { VMALLOC_START,        "vmalloc() Area" },
  47         { VMEMMAP_START,        "Vmemmap" },
  48         { __START_KERNEL_map,   "High Kernel Mapping" },
  49         { MODULES_VADDR,        "Modules" },
  50         { MODULES_END,          "End Modules" },
  51 #else
  52         { PAGE_OFFSET,          "Kernel Mapping" },
  53         { 0/* VMALLOC_START */, "vmalloc() Area" },
  54         { 0/*VMALLOC_END*/,     "vmalloc() End" },
  55 # ifdef CONFIG_HIGHMEM
  56         { 0/*PKMAP_BASE*/,      "Persisent kmap() Area" },
  57 # endif
  58         { 0/*FIXADDR_START*/,   "Fixmap Area" },
  59 #endif
  60         { -1, NULL }            /* End of list */
  61 };
  62
  63 /* Multipliers for offsets within the PTEs */
  64 #define PTE_LEVEL_MULT (PAGE_SIZE)
  65 #define PMD_LEVEL_MULT (PTRS_PER_PTE * PTE_LEVEL_MULT)
  66 #define PUD_LEVEL_MULT (PTRS_PER_PMD * PMD_LEVEL_MULT)
  67 #define PGD_LEVEL_MULT (PTRS_PER_PUD * PUD_LEVEL_MULT)
  68
  69 /*
  70  * Print a readable form of a pgprot_t to the seq_file
  71  */
  72 static void printk_prot(struct seq_file *m, pgprot_t prot, int level)
  73 {
  74         pgprotval_t pr = pgprot_val(prot);
  75         static const char * const level_name[] =
  76                 { "cr3", "pgd", "pud", "pmd", "pte" };
  77
  78         if (!pgprot_val(prot)) {
  79                 /* Not present */
  80                 seq_printf(m, "                          ");
  81         } else {
  82                 if (pr & _PAGE_USER)
  83                         seq_printf(m, "USR ");
  84                 else
  85                         seq_printf(m, "    ");
  86                 if (pr & _PAGE_RW)
  87                         seq_printf(m, "RW ");
  88                 else
  89                         seq_printf(m, "ro ");
  90                 if (pr & _PAGE_PWT)
  91                         seq_printf(m, "PWT ");
  92                 else
  93                         seq_printf(m, "    ");
  94                 if (pr & _PAGE_PCD)
  95                         seq_printf(m, "PCD ");
  96                 else
  97                         seq_printf(m, "    ");
  98
  99                 /* Bit 9 has a different meaning on level 3 vs 4 */
 100                 if (level <= 3) {
 101                         if (pr & _PAGE_PSE)
 102                                 seq_printf(m, "PSE ");
 103                         else
 104                                 seq_printf(m, "    ");
 105                 } else {
 106                         if (pr & _PAGE_PAT)
 107                                 seq_printf(m, "pat ");
 108                         else
 109                                 seq_printf(m, "    ");
 110                 }
 111                 if (pr & _PAGE_GLOBAL)
 112                         seq_printf(m, "GLB ");
 113                 else
 114                         seq_printf(m, "    ");
 115                 if (pr & _PAGE_NX)
 116                         seq_printf(m, "NX ");
 117                 else
 118                         seq_printf(m, "x  ");
 119         }
 120         seq_printf(m, "%s\n", level_name[level]);
 121 }
 122
 123 /*
 124  * On 64 bits, sign-extend the 48 bit address to 64 bit
 125  */
 126 static unsigned long normalize_addr(unsigned long u)
 127 {
 128 #ifdef CONFIG_X86_64
 129         return (signed long)(u << 16) >> 16;
 130 #else
 131         return u;
 132 #endif
 133 }
 134
 135 /*
 136  * This function gets called on a break in a continuous series
 137  * of PTE entries; the next one is different so we need to
 138  * print what we collected so far.
 139  */
 140 static void note_page(struct seq_file *m, struct pg_state *st,
 141                       pgprot_t new_prot, int level)
 142 {
 143         pgprotval_t prot, cur;
 144         static const char units[] = "KMGTPE";
 145
 146         /*
 147          * If we have a "break" in the series, we need to flush the state that
 148          * we have now. "break" is either changing perms, levels or
 149          * address space marker.
 150          */
 151         prot = pgprot_val(new_prot) & PTE_FLAGS_MASK;
 152         cur = pgprot_val(st->current_prot) & PTE_FLAGS_MASK;
 153
 154         if (!st->level) {
 155                 /* First entry */
 156                 st->current_prot = new_prot;
 157                 st->level = level;
 158                 st->marker = address_markers;
 159                 seq_printf(m, "---[ %s ]---\n", st->marker->name);
 160         } else if (prot != cur || level != st->level ||
 161                    st->current_address >= st->marker[1].start_address) {
 162                 const char *unit = units;
 163                 unsigned long delta;
 164
 165                 /*
 166                  * Now print the actual finished series
 167                  */
 168                 seq_printf(m, "0x%p-0x%p   ",
 169                            (void *)st->start_address,
 170                            (void *)st->current_address);
 171
 172                 delta = (st->current_address - st->start_address) >> 10;
 173                 while (!(delta & 1023) && unit[1]) {
 174                         delta >>= 10;
 175                         unit++;
 176                 }
 177                 seq_printf(m, "%9lu%c ", delta, *unit);
 178                 printk_prot(m, st->current_prot, st->level);
 179
 180                 /*
 181                  * We print markers for special areas of address space,
 182                  * such as the start of vmalloc space etc.
 183                  * This helps in the interpretation.
 184                  */
 185                 if (st->current_address >= st->marker[1].start_address) {
 186                         st->marker++;
 187                         seq_printf(m, "---[ %s ]---\n", st->marker->name);
 188                 }
 189
 190                 st->start_address = st->current_address;
 191                 st->current_prot = new_prot;
 192                 st->level = level;
 193         }
 194 }
 195
 196 static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr,
 197                                                         unsigned long P)
 198 {
 199         int i;
 200         pte_t *start;
 201
 202         start = (pte_t *) pmd_page_vaddr(addr);
 203         for (i = 0; i < PTRS_PER_PTE; i++) {
 204                 pgprot_t prot = pte_pgprot(*start);
 205
 206                 st->current_address = normalize_addr(P + i * PTE_LEVEL_MULT);
 207                 note_page(m, st, prot, 4);
 208                 start++;
 209         }
 210 }
 211
 212 #if PTRS_PER_PMD > 1
 213
 214 static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr,
 215                                                         unsigned long P)
 216 {
 217         int i;
 218         pmd_t *start;
 219
 220         start = (pmd_t *) pud_page_vaddr(addr);
 221         for (i = 0; i < PTRS_PER_PMD; i++) {
 222                 st->current_address = normalize_addr(P + i * PMD_LEVEL_MULT);
 223                 if (!pmd_none(*start)) {
 224                         pgprotval_t prot = pmd_val(*start) & PTE_FLAGS_MASK;
 225
 226                         if (pmd_large(*start) || !pmd_present(*start))
 227                                 note_page(m, st, __pgprot(prot), 3);
 228                         else
 229                                 walk_pte_level(m, st, *start,
 230                                                P + i * PMD_LEVEL_MULT);
 231                 } else
 232                         note_page(m, st, __pgprot(0), 3);
 233                 start++;
 234         }
 235 }
 236
 237 #else
 238 #define walk_pmd_level(m,s,a,p) walk_pte_level(m,s,__pmd(pud_val(a)),p)
 239 #define pud_large(a) pmd_large(__pmd(pud_val(a)))
 240 #define pud_none(a)  pmd_none(__pmd(pud_val(a)))
 241 #endif
 242
 243 #if PTRS_PER_PUD > 1
 244
 245 static void walk_pud_level(struct seq_file *m, struct pg_state *st, pgd_t addr,
 246                                                         unsigned long P)
 247 {
 248         int i;
 249         pud_t *start;
 250
 251         start = (pud_t *) pgd_page_vaddr(addr);
 252
 253         for (i = 0; i < PTRS_PER_PUD; i++) {
 254                 st->current_address = normalize_addr(P + i * PUD_LEVEL_MULT);
 255                 if (!pud_none(*start)) {
 256                         pgprotval_t prot = pud_val(*start) & PTE_FLAGS_MASK;
 257
 258                         if (pud_large(*start) || !pud_present(*start))
 259                                 note_page(m, st, __pgprot(prot), 2);
 260                         else
 261                                 walk_pmd_level(m, st, *start,
 262                                                P + i * PUD_LEVEL_MULT);
 263                 } else
 264                         note_page(m, st, __pgprot(0), 2);
 265
 266                 start++;
 267         }
 268 }
 269
 270 #else
 271 #define walk_pud_level(m,s,a,p) walk_pmd_level(m,s,__pud(pgd_val(a)),p)
 272 #define pgd_large(a) pud_large(__pud(pgd_val(a)))
 273 #define pgd_none(a)  pud_none(__pud(pgd_val(a)))
 274 #endif
 275
 276 static void walk_pgd_level(struct seq_file *m)
 277 {
 278 #ifdef CONFIG_X86_64
 279         pgd_t *start = (pgd_t *) &init_level4_pgt;
 280 #else
 281         pgd_t *start = swapper_pg_dir;
 282 #endif
 283         int i;
 284         struct pg_state st;
 285
 286         memset(&st, 0, sizeof(st));
 287
 288         for (i = 0; i < PTRS_PER_PGD; i++) {
 289                 st.current_address = normalize_addr(i * PGD_LEVEL_MULT);
 290                 if (!pgd_none(*start)) {
 291                         pgprotval_t prot = pgd_val(*start) & PTE_FLAGS_MASK;
 292
 293                         if (pgd_large(*start) || !pgd_present(*start))
 294                                 note_page(m, &st, __pgprot(prot), 1);
 295                         else
 296                                 walk_pud_level(m, &st, *start,
 297                                                i * PGD_LEVEL_MULT);
 298                 } else
 299                         note_page(m, &st, __pgprot(0), 1);
 300
 301                 start++;
 302         }
 303
 304         /* Flush out the last page */
 305         st.current_address = normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT);
 306         note_page(m, &st, __pgprot(0), 0);
 307 }
 308
 309 static int ptdump_show(struct seq_file *m, void *v)
 310 {
 311         walk_pgd_level(m);
 312         return 0;
 313 }
 314
 315 static int ptdump_open(struct inode *inode, struct file *filp)
 316 {
 317         return single_open(filp, ptdump_show, NULL);
 318 }
 319
 320 static const struct file_operations ptdump_fops = {
 321         .open           = ptdump_open,
 322         .read           = seq_read,
 323         .llseek         = seq_lseek,
 324         .release        = single_release,
 325 };
 326
 327 static int pt_dump_init(void)
 328 {
 329         struct dentry *pe;
 330
 331 #ifdef CONFIG_X86_32
 332         /* Not a compile-time constant on x86-32 */
 333         address_markers[2].start_address = VMALLOC_START;
 334         address_markers[3].start_address = VMALLOC_END;
 335 # ifdef CONFIG_HIGHMEM
 336         address_markers[4].start_address = PKMAP_BASE;
 337         address_markers[5].start_address = FIXADDR_START;
 338 # else
 339         address_markers[4].start_address = FIXADDR_START;
 340 # endif
 341 #endif
 342
 343         pe = debugfs_create_file("kernel_page_tables", 0600, NULL, NULL,
 344                                  &ptdump_fops);
 345         if (!pe)
 346                 return -ENOMEM;
 347
 348         return 0;
 349 }
 350
 351 __initcall(pt_dump_init);
 352 MODULE_LICENSE("GPL");
 353 MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>");
 354 MODULE_DESCRIPTION("Kernel debugging helper that dumps pagetables");