LXR linux/arch/x86/mm/dump

   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 */
  29struct 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
  41struct 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 */
  48enum 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 */
  77static 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 P4D_LEVEL_MULT (PTRS_PER_PUD * PUD_LEVEL_MULT)
 114#define PGD_LEVEL_MULT (PTRS_PER_P4D * P4D_LEVEL_MULT)
 115
 116#define pt_dump_seq_printf(m, to_dmesg, fmt, args...)           \
 117({                                                              \
 118        if (to_dmesg)                                   \
 119                printk(KERN_INFO fmt, ##args);                  \
 120        else                                                    \
 121                if (m)                                          \
 122                        seq_printf(m, fmt, ##args);             \
 123})
 124
 125#define pt_dump_cont_printf(m, to_dmesg, fmt, args...)          \
 126({                                                              \
 127        if (to_dmesg)                                   \
 128                printk(KERN_CONT fmt, ##args);                  \
 129        else                                                    \
 130                if (m)                                          \
 131                        seq_printf(m, fmt, ##args);             \
 132})
 133
 134/*
 135 * Print a readable form of a pgprot_t to the seq_file
 136 */
 137static void printk_prot(struct seq_file *m, pgprot_t prot, int level, bool dmsg)
 138{
 139        pgprotval_t pr = pgprot_val(prot);
 140        static const char * const level_name[] =
 141                { "cr3", "pgd", "pud", "pmd", "pte" };
 142
 143        if (!pgprot_val(prot)) {
 144                /* Not present */
 145                pt_dump_cont_printf(m, dmsg, "                              ");
 146        } else {
 147                if (pr & _PAGE_USER)
 148                        pt_dump_cont_printf(m, dmsg, "USR ");
 149                else
 150                        pt_dump_cont_printf(m, dmsg, "    ");
 151                if (pr & _PAGE_RW)
 152                        pt_dump_cont_printf(m, dmsg, "RW ");
 153                else
 154                        pt_dump_cont_printf(m, dmsg, "ro ");
 155                if (pr & _PAGE_PWT)
 156                        pt_dump_cont_printf(m, dmsg, "PWT ");
 157                else
 158                        pt_dump_cont_printf(m, dmsg, "    ");
 159                if (pr & _PAGE_PCD)
 160                        pt_dump_cont_printf(m, dmsg, "PCD ");
 161                else
 162                        pt_dump_cont_printf(m, dmsg, "    ");
 163
 164                /* Bit 7 has a different meaning on level 3 vs 4 */
 165                if (level <= 3 && pr & _PAGE_PSE)
 166                        pt_dump_cont_printf(m, dmsg, "PSE ");
 167                else
 168                        pt_dump_cont_printf(m, dmsg, "    ");
 169                if ((level == 4 && pr & _PAGE_PAT) ||
 170                    ((level == 3 || level == 2) && pr & _PAGE_PAT_LARGE))
 171                        pt_dump_cont_printf(m, dmsg, "PAT ");
 172                else
 173                        pt_dump_cont_printf(m, dmsg, "    ");
 174                if (pr & _PAGE_GLOBAL)
 175                        pt_dump_cont_printf(m, dmsg, "GLB ");
 176                else
 177                        pt_dump_cont_printf(m, dmsg, "    ");
 178                if (pr & _PAGE_NX)
 179                        pt_dump_cont_printf(m, dmsg, "NX ");
 180                else
 181                        pt_dump_cont_printf(m, dmsg, "x  ");
 182        }
 183        pt_dump_cont_printf(m, dmsg, "%s\n", level_name[level]);
 184}
 185
 186/*
 187 * On 64 bits, sign-extend the 48 bit address to 64 bit
 188 */
 189static unsigned long normalize_addr(unsigned long u)
 190{
 191#ifdef CONFIG_X86_64
 192        return (signed long)(u << 16) >> 16;
 193#else
 194        return u;
 195#endif
 196}
 197
 198/*
 199 * This function gets called on a break in a continuous series
 200 * of PTE entries; the next one is different so we need to
 201 * print what we collected so far.
 202 */
 203static void note_page(struct seq_file *m, struct pg_state *st,
 204                      pgprot_t new_prot, int level)
 205{
 206        pgprotval_t prot, cur;
 207        static const char units[] = "BKMGTPE";
 208
 209        /*
 210         * If we have a "break" in the series, we need to flush the state that
 211         * we have now. "break" is either changing perms, levels or
 212         * address space marker.
 213         */
 214        prot = pgprot_val(new_prot);
 215        cur = pgprot_val(st->current_prot);
 216
 217        if (!st->level) {
 218                /* First entry */
 219                st->current_prot = new_prot;
 220                st->level = level;
 221                st->marker = address_markers;
 222                st->lines = 0;
 223                pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
 224                                   st->marker->name);
 225        } else if (prot != cur || level != st->level ||
 226                   st->current_address >= st->marker[1].start_address) {
 227                const char *unit = units;
 228                unsigned long delta;
 229                int width = sizeof(unsigned long) * 2;
 230                pgprotval_t pr = pgprot_val(st->current_prot);
 231
 232                if (st->check_wx && (pr & _PAGE_RW) && !(pr & _PAGE_NX)) {
 233                        WARN_ONCE(1,
 234                                  "x86/mm: Found insecure W+X mapping at address %p/%pS\n",
 235                                  (void *)st->start_address,
 236                                  (void *)st->start_address);
 237                        st->wx_pages += (st->current_address -
 238                                         st->start_address) / PAGE_SIZE;
 239                }
 240
 241                /*
 242                 * Now print the actual finished series
 243                 */
 244                if (!st->marker->max_lines ||
 245                    st->lines < st->marker->max_lines) {
 246                        pt_dump_seq_printf(m, st->to_dmesg,
 247                                           "0x%0*lx-0x%0*lx   ",
 248                                           width, st->start_address,
 249                                           width, st->current_address);
 250
 251                        delta = st->current_address - st->start_address;
 252                        while (!(delta & 1023) && unit[1]) {
 253                                delta >>= 10;
 254                                unit++;
 255                        }
 256                        pt_dump_cont_printf(m, st->to_dmesg, "%9lu%c ",
 257                                            delta, *unit);
 258                        printk_prot(m, st->current_prot, st->level,
 259                                    st->to_dmesg);
 260                }
 261                st->lines++;
 262
 263                /*
 264                 * We print markers for special areas of address space,
 265                 * such as the start of vmalloc space etc.
 266                 * This helps in the interpretation.
 267                 */
 268                if (st->current_address >= st->marker[1].start_address) {
 269                        if (st->marker->max_lines &&
 270                            st->lines > st->marker->max_lines) {
 271                                unsigned long nskip =
 272                                        st->lines - st->marker->max_lines;
 273                                pt_dump_seq_printf(m, st->to_dmesg,
 274                                                   "... %lu entr%s skipped ... \n",
 275                                                   nskip,
 276                                                   nskip == 1 ? "y" : "ies");
 277                        }
 278                        st->marker++;
 279                        st->lines = 0;
 280                        pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
 281                                           st->marker->name);
 282                }
 283
 284                st->start_address = st->current_address;
 285                st->current_prot = new_prot;
 286                st->level = level;
 287        }
 288}
 289
 290static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr, 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
 307static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr, unsigned long P)
 308{
 309        int i;
 310        pmd_t *start;
 311        pgprotval_t prot;
 312
 313        start = (pmd_t *)pud_page_vaddr(addr);
 314        for (i = 0; i < PTRS_PER_PMD; i++) {
 315                st->current_address = normalize_addr(P + i * PMD_LEVEL_MULT);
 316                if (!pmd_none(*start)) {
 317                        if (pmd_large(*start) || !pmd_present(*start)) {
 318                                prot = pmd_flags(*start);
 319                                note_page(m, st, __pgprot(prot), 3);
 320                        } else {
 321                                walk_pte_level(m, st, *start,
 322                                               P + i * PMD_LEVEL_MULT);
 323                        }
 324                } else
 325                        note_page(m, st, __pgprot(0), 3);
 326                start++;
 327        }
 328}
 329
 330#else
 331#define walk_pmd_level(m,s,a,p) walk_pte_level(m,s,__pmd(pud_val(a)),p)
 332#define pud_large(a) pmd_large(__pmd(pud_val(a)))
 333#define pud_none(a)  pmd_none(__pmd(pud_val(a)))
 334#endif
 335
 336#if PTRS_PER_PUD > 1
 337
 338/*
 339 * This is an optimization for CONFIG_DEBUG_WX=y + CONFIG_KASAN=y
 340 * KASAN fills page tables with the same values. Since there is no
 341 * point in checking page table more than once we just skip repeated
 342 * entries. This saves us dozens of seconds during boot.
 343 */
 344static bool pud_already_checked(pud_t *prev_pud, pud_t *pud, bool checkwx)
 345{
 346        return checkwx && prev_pud && (pud_val(*prev_pud) == pud_val(*pud));
 347}
 348
 349static void walk_pud_level(struct seq_file *m, struct pg_state *st, p4d_t addr, unsigned long P)
 350{
 351        int i;
 352        pud_t *start;
 353        pgprotval_t prot;
 354        pud_t *prev_pud = NULL;
 355
 356        start = (pud_t *)p4d_page_vaddr(addr);
 357
 358        for (i = 0; i < PTRS_PER_PUD; i++) {
 359                st->current_address = normalize_addr(P + i * PUD_LEVEL_MULT);
 360                if (!pud_none(*start) &&
 361                    !pud_already_checked(prev_pud, start, st->check_wx)) {
 362                        if (pud_large(*start) || !pud_present(*start)) {
 363                                prot = pud_flags(*start);
 364                                note_page(m, st, __pgprot(prot), 2);
 365                        } else {
 366                                walk_pmd_level(m, st, *start,
 367                                               P + i * PUD_LEVEL_MULT);
 368                        }
 369                } else
 370                        note_page(m, st, __pgprot(0), 2);
 371
 372                prev_pud = start;
 373                start++;
 374        }
 375}
 376
 377#else
 378#define walk_pud_level(m,s,a,p) walk_pmd_level(m,s,__pud(p4d_val(a)),p)
 379#define p4d_large(a) pud_large(__pud(p4d_val(a)))
 380#define p4d_none(a)  pud_none(__pud(p4d_val(a)))
 381#endif
 382
 383#if PTRS_PER_P4D > 1
 384
 385static void walk_p4d_level(struct seq_file *m, struct pg_state *st, pgd_t addr, unsigned long P)
 386{
 387        int i;
 388        p4d_t *start;
 389        pgprotval_t prot;
 390
 391        start = (p4d_t *)pgd_page_vaddr(addr);
 392
 393        for (i = 0; i < PTRS_PER_P4D; i++) {
 394                st->current_address = normalize_addr(P + i * P4D_LEVEL_MULT);
 395                if (!p4d_none(*start)) {
 396                        if (p4d_large(*start) || !p4d_present(*start)) {
 397                                prot = p4d_flags(*start);
 398                                note_page(m, st, __pgprot(prot), 2);
 399                        } else {
 400                                walk_pud_level(m, st, *start,
 401                                               P + i * P4D_LEVEL_MULT);
 402                        }
 403                } else
 404                        note_page(m, st, __pgprot(0), 2);
 405
 406                start++;
 407        }
 408}
 409
 410#else
 411#define walk_p4d_level(m,s,a,p) walk_pud_level(m,s,__p4d(pgd_val(a)),p)
 412#define pgd_large(a) p4d_large(__p4d(pgd_val(a)))
 413#define pgd_none(a)  p4d_none(__p4d(pgd_val(a)))
 414#endif
 415
 416static inline bool is_hypervisor_range(int idx)
 417{
 418#ifdef CONFIG_X86_64
 419        /*
 420         * ffff800000000000 - ffff87ffffffffff is reserved for
 421         * the hypervisor.
 422         */
 423        return  (idx >= pgd_index(__PAGE_OFFSET) - 16) &&
 424                (idx <  pgd_index(__PAGE_OFFSET));
 425#else
 426        return false;
 427#endif
 428}
 429
 430static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 431                                       bool checkwx)
 432{
 433#ifdef CONFIG_X86_64
 434        pgd_t *start = (pgd_t *) &init_top_pgt;
 435#else
 436        pgd_t *start = swapper_pg_dir;
 437#endif
 438        pgprotval_t prot;
 439        int i;
 440        struct pg_state st = {};
 441
 442        if (pgd) {
 443                start = pgd;
 444                st.to_dmesg = true;
 445        }
 446
 447        st.check_wx = checkwx;
 448        if (checkwx)
 449                st.wx_pages = 0;
 450
 451        for (i = 0; i < PTRS_PER_PGD; i++) {
 452                st.current_address = normalize_addr(i * PGD_LEVEL_MULT);
 453                if (!pgd_none(*start) && !is_hypervisor_range(i)) {
 454                        if (pgd_large(*start) || !pgd_present(*start)) {
 455                                prot = pgd_flags(*start);
 456                                note_page(m, &st, __pgprot(prot), 1);
 457                        } else {
 458                                walk_p4d_level(m, &st, *start,
 459                                               i * PGD_LEVEL_MULT);
 460                        }
 461                } else
 462                        note_page(m, &st, __pgprot(0), 1);
 463
 464                cond_resched();
 465                start++;
 466        }
 467
 468        /* Flush out the last page */
 469        st.current_address = normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT);
 470        note_page(m, &st, __pgprot(0), 0);
 471        if (!checkwx)
 472                return;
 473        if (st.wx_pages)
 474                pr_info("x86/mm: Checked W+X mappings: FAILED, %lu W+X pages found.\n",
 475                        st.wx_pages);
 476        else
 477                pr_info("x86/mm: Checked W+X mappings: passed, no W+X pages found.\n");
 478}
 479
 480void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd)
 481{
 482        ptdump_walk_pgd_level_core(m, pgd, false);
 483}
 484EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level);
 485
 486void ptdump_walk_pgd_level_checkwx(void)
 487{
 488        ptdump_walk_pgd_level_core(NULL, NULL, true);
 489}
 490
 491static int __init pt_dump_init(void)
 492{
 493        /*
 494         * Various markers are not compile-time constants, so assign them
 495         * here.
 496         */
 497#ifdef CONFIG_X86_64
 498        address_markers[LOW_KERNEL_NR].start_address = PAGE_OFFSET;
 499        address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
 500        address_markers[VMEMMAP_START_NR].start_address = VMEMMAP_START;
 501#endif
 502#ifdef CONFIG_X86_32
 503        address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
 504        address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
 505# ifdef CONFIG_HIGHMEM
 506        address_markers[PKMAP_BASE_NR].start_address = PKMAP_BASE;
 507# endif
 508        address_markers[FIXADDR_START_NR].start_address = FIXADDR_START;
 509#endif
 510
 511        return 0;
 512}
 513__initcall(pt_dump_init);
 514