1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Debug helper to dump the current kernel pagetables of the system
4 * so that we can see what the various memory ranges are set to.
5 *
6 * (C) Copyright 2008 Intel Corporation
7 *
8 * Author: Arjan van de Ven <arjan@linux.intel.com>
9 */
10
11#include <linux/debugfs.h>
12#include <linux/kasan.h>
13#include <linux/mm.h>
14#include <linux/init.h>
15#include <linux/sched.h>
16#include <linux/seq_file.h>
17#include <linux/highmem.h>
18#include <linux/pci.h>
19#include <linux/ptdump.h>
20
21#include <asm/e820/types.h>
22
23/*
24 * The dumper groups pagetable entries of the same type into one, and for
25 * that it needs to keep some state when walking, and flush this state
26 * when a "break" in the continuity is found.
27 */
28struct pg_state {
29 struct ptdump_state ptdump;
30 int level;
31 pgprotval_t current_prot;
32 pgprotval_t effective_prot;
33 pgprotval_t prot_levels[5];
34 unsigned long start_address;
35 const struct addr_marker *marker;
36 unsigned long lines;
37 bool to_dmesg;
38 bool check_wx;
39 unsigned long wx_pages;
40 struct seq_file *seq;
41};
42
43struct addr_marker {
44 unsigned long start_address;
45 const char *name;
46 unsigned long max_lines;
47};
48
49/* Address space markers hints */
50
51#ifdef CONFIG_X86_64
52
53enum address_markers_idx {
54 USER_SPACE_NR = 0,
55 KERNEL_SPACE_NR,
56#ifdef CONFIG_MODIFY_LDT_SYSCALL
57 LDT_NR,
58#endif
59 LOW_KERNEL_NR,
60 VMALLOC_START_NR,
61 VMEMMAP_START_NR,
62#ifdef CONFIG_KASAN
63 KASAN_SHADOW_START_NR,
64 KASAN_SHADOW_END_NR,
65#endif
66 CPU_ENTRY_AREA_NR,
67#ifdef CONFIG_X86_ESPFIX64
68 ESPFIX_START_NR,
69#endif
70#ifdef CONFIG_EFI
71 EFI_END_NR,
72#endif
73 HIGH_KERNEL_NR,
74 MODULES_VADDR_NR,
75 MODULES_END_NR,
76 FIXADDR_START_NR,
77 END_OF_SPACE_NR,
78};
79
80static struct addr_marker address_markers[] = {
81 [USER_SPACE_NR] = { 0, "User Space" },
82 [KERNEL_SPACE_NR] = { (1UL << 63), "Kernel Space" },
83 [LOW_KERNEL_NR] = { 0UL, "Low Kernel Mapping" },
84 [VMALLOC_START_NR] = { 0UL, "vmalloc() Area" },
85 [VMEMMAP_START_NR] = { 0UL, "Vmemmap" },
86#ifdef CONFIG_KASAN
87 /*
88 * These fields get initialized with the (dynamic)
89 * KASAN_SHADOW_{START,END} values in pt_dump_init().
90 */
91 [KASAN_SHADOW_START_NR] = { 0UL, "KASAN shadow" },
92 [KASAN_SHADOW_END_NR] = { 0UL, "KASAN shadow end" },
93#endif
94#ifdef CONFIG_MODIFY_LDT_SYSCALL
95 [LDT_NR] = { 0UL, "LDT remap" },
96#endif
97 [CPU_ENTRY_AREA_NR] = { CPU_ENTRY_AREA_BASE,"CPU entry Area" },
98#ifdef CONFIG_X86_ESPFIX64
99 [ESPFIX_START_NR] = { ESPFIX_BASE_ADDR, "ESPfix Area", 16 },
100#endif
101#ifdef CONFIG_EFI
102 [EFI_END_NR] = { EFI_VA_END, "EFI Runtime Services" },
103#endif
104 [HIGH_KERNEL_NR] = { __START_KERNEL_map, "High Kernel Mapping" },
105 [MODULES_VADDR_NR] = { MODULES_VADDR, "Modules" },
106 [MODULES_END_NR] = { MODULES_END, "End Modules" },
107 [FIXADDR_START_NR] = { FIXADDR_START, "Fixmap Area" },
108 [END_OF_SPACE_NR] = { -1, NULL }
109};
110
111#define INIT_PGD ((pgd_t *) &init_top_pgt)
112
113#else /* CONFIG_X86_64 */
114
115enum address_markers_idx {
116 USER_SPACE_NR = 0,
117 KERNEL_SPACE_NR,
118 VMALLOC_START_NR,
119 VMALLOC_END_NR,
120#ifdef CONFIG_HIGHMEM
121 PKMAP_BASE_NR,
122#endif
123#ifdef CONFIG_MODIFY_LDT_SYSCALL
124 LDT_NR,
125#endif
126 CPU_ENTRY_AREA_NR,
127 FIXADDR_START_NR,
128 END_OF_SPACE_NR,
129};
130
131static struct addr_marker address_markers[] = {
132 [USER_SPACE_NR] = { 0, "User Space" },
133 [KERNEL_SPACE_NR] = { PAGE_OFFSET, "Kernel Mapping" },
134 [VMALLOC_START_NR] = { 0UL, "vmalloc() Area" },
135 [VMALLOC_END_NR] = { 0UL, "vmalloc() End" },
136#ifdef CONFIG_HIGHMEM
137 [PKMAP_BASE_NR] = { 0UL, "Persistent kmap() Area" },
138#endif
139#ifdef CONFIG_MODIFY_LDT_SYSCALL
140 [LDT_NR] = { 0UL, "LDT remap" },
141#endif
142 [CPU_ENTRY_AREA_NR] = { 0UL, "CPU entry area" },
143 [FIXADDR_START_NR] = { 0UL, "Fixmap area" },
144 [END_OF_SPACE_NR] = { -1, NULL }
145};
146
147#define INIT_PGD (swapper_pg_dir)
148
149#endif /* !CONFIG_X86_64 */
150
151/* Multipliers for offsets within the PTEs */
152#define PTE_LEVEL_MULT (PAGE_SIZE)
153#define PMD_LEVEL_MULT (PTRS_PER_PTE * PTE_LEVEL_MULT)
154#define PUD_LEVEL_MULT (PTRS_PER_PMD * PMD_LEVEL_MULT)
155#define P4D_LEVEL_MULT (PTRS_PER_PUD * PUD_LEVEL_MULT)
156#define PGD_LEVEL_MULT (PTRS_PER_P4D * P4D_LEVEL_MULT)
157
158#define pt_dump_seq_printf(m, to_dmesg, fmt, args...) \
159({ \
160 if (to_dmesg) \
161 printk(KERN_INFO fmt, ##args); \
162 else \
163 if (m) \
164 seq_printf(m, fmt, ##args); \
165})
166
167#define pt_dump_cont_printf(m, to_dmesg, fmt, args...) \
168({ \
169 if (to_dmesg) \
170 printk(KERN_CONT fmt, ##args); \
171 else \
172 if (m) \
173 seq_printf(m, fmt, ##args); \
174})
175
176/*
177 * Print a readable form of a pgprot_t to the seq_file
178 */
179static void printk_prot(struct seq_file *m, pgprotval_t pr, int level, bool dmsg)
180{
181 static const char * const level_name[] =
182 { "pgd", "p4d", "pud", "pmd", "pte" };
183
184 if (!(pr & _PAGE_PRESENT)) {
185 /* Not present */
186 pt_dump_cont_printf(m, dmsg, " ");
187 } else {
188 if (pr & _PAGE_USER)
189 pt_dump_cont_printf(m, dmsg, "USR ");
190 else
191 pt_dump_cont_printf(m, dmsg, " ");
192 if (pr & _PAGE_RW)
193 pt_dump_cont_printf(m, dmsg, "RW ");
194 else
195 pt_dump_cont_printf(m, dmsg, "ro ");
196 if (pr & _PAGE_PWT)
197 pt_dump_cont_printf(m, dmsg, "PWT ");
198 else
199 pt_dump_cont_printf(m, dmsg, " ");
200 if (pr & _PAGE_PCD)
201 pt_dump_cont_printf(m, dmsg, "PCD ");
202 else
203 pt_dump_cont_printf(m, dmsg, " ");
204
205 /* Bit 7 has a different meaning on level 3 vs 4 */
206 if (level <= 3 && pr & _PAGE_PSE)
207 pt_dump_cont_printf(m, dmsg, "PSE ");
208 else
209 pt_dump_cont_printf(m, dmsg, " ");
210 if ((level == 4 && pr & _PAGE_PAT) ||
211 ((level == 3 || level == 2) && pr & _PAGE_PAT_LARGE))
212 pt_dump_cont_printf(m, dmsg, "PAT ");
213 else
214 pt_dump_cont_printf(m, dmsg, " ");
215 if (pr & _PAGE_GLOBAL)
216 pt_dump_cont_printf(m, dmsg, "GLB ");
217 else
218 pt_dump_cont_printf(m, dmsg, " ");
219 if (pr & _PAGE_NX)
220 pt_dump_cont_printf(m, dmsg, "NX ");
221 else
222 pt_dump_cont_printf(m, dmsg, "x ");
223 }
224 pt_dump_cont_printf(m, dmsg, "%s\n", level_name[level]);
225}
226
227static void note_wx(struct pg_state *st, unsigned long addr)
228{
229 unsigned long npages;
230
231 npages = (addr - st->start_address) / PAGE_SIZE;
232
233#ifdef CONFIG_PCI_BIOS
234 /*
235 * If PCI BIOS is enabled, the PCI BIOS area is forced to WX.
236 * Inform about it, but avoid the warning.
237 */
238 if (pcibios_enabled && st->start_address >= PAGE_OFFSET + BIOS_BEGIN &&
239 addr <= PAGE_OFFSET + BIOS_END) {
240 pr_warn_once("x86/mm: PCI BIOS W+X mapping %lu pages\n", npages);
241 return;
242 }
243#endif
244 /* Account the WX pages */
245 st->wx_pages += npages;
246 WARN_ONCE(__supported_pte_mask & _PAGE_NX,
247 "x86/mm: Found insecure W+X mapping at address %pS\n",
248 (void *)st->start_address);
249}
250
251static void effective_prot(struct ptdump_state *pt_st, int level, u64 val)
252{
253 struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
254 pgprotval_t prot = val & PTE_FLAGS_MASK;
255 pgprotval_t effective;
256
257 if (level > 0) {
258 pgprotval_t higher_prot = st->prot_levels[level - 1];
259
260 effective = (higher_prot & prot & (_PAGE_USER | _PAGE_RW)) |
261 ((higher_prot | prot) & _PAGE_NX);
262 } else {
263 effective = prot;
264 }
265
266 st->prot_levels[level] = effective;
267}
268
269static void effective_prot_pte(struct ptdump_state *st, pte_t pte)
270{
271 effective_prot(pt_st: st, level: 4, val: pte_val(pte));
272}
273
274static void effective_prot_pmd(struct ptdump_state *st, pmd_t pmd)
275{
276 effective_prot(pt_st: st, level: 3, val: pmd_val(pmd));
277}
278
279static void effective_prot_pud(struct ptdump_state *st, pud_t pud)
280{
281 effective_prot(pt_st: st, level: 2, val: pud_val(pud));
282}
283
284static void effective_prot_p4d(struct ptdump_state *st, p4d_t p4d)
285{
286 effective_prot(pt_st: st, level: 1, val: p4d_val(p4d));
287}
288
289static void effective_prot_pgd(struct ptdump_state *st, pgd_t pgd)
290{
291 effective_prot(pt_st: st, level: 0, val: pgd_val(pgd));
292}
293
294
295/*
296 * This function gets called on a break in a continuous series
297 * of PTE entries; the next one is different so we need to
298 * print what we collected so far.
299 */
300static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
301 u64 val)
302{
303 struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
304 pgprotval_t new_prot, new_eff;
305 pgprotval_t cur, eff;
306 static const char units[] = "BKMGTPE";
307 struct seq_file *m = st->seq;
308
309 new_prot = val & PTE_FLAGS_MASK;
310 if (!val)
311 new_eff = 0;
312 else
313 new_eff = st->prot_levels[level];
314
315 /*
316 * If we have a "break" in the series, we need to flush the state that
317 * we have now. "break" is either changing perms, levels or
318 * address space marker.
319 */
320 cur = st->current_prot;
321 eff = st->effective_prot;
322
323 if (st->level == -1) {
324 /* First entry */
325 st->current_prot = new_prot;
326 st->effective_prot = new_eff;
327 st->level = level;
328 st->marker = address_markers;
329 st->lines = 0;
330 pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
331 st->marker->name);
332 } else if (new_prot != cur || new_eff != eff || level != st->level ||
333 addr >= st->marker[1].start_address) {
334 const char *unit = units;
335 unsigned long delta;
336 int width = sizeof(unsigned long) * 2;
337
338 if (st->check_wx && (eff & _PAGE_RW) && !(eff & _PAGE_NX))
339 note_wx(st, addr);
340
341 /*
342 * Now print the actual finished series
343 */
344 if (!st->marker->max_lines ||
345 st->lines < st->marker->max_lines) {
346 pt_dump_seq_printf(m, st->to_dmesg,
347 "0x%0*lx-0x%0*lx ",
348 width, st->start_address,
349 width, addr);
350
351 delta = addr - st->start_address;
352 while (!(delta & 1023) && unit[1]) {
353 delta >>= 10;
354 unit++;
355 }
356 pt_dump_cont_printf(m, st->to_dmesg, "%9lu%c ",
357 delta, *unit);
358 printk_prot(m, pr: st->current_prot, level: st->level,
359 dmsg: st->to_dmesg);
360 }
361 st->lines++;
362
363 /*
364 * We print markers for special areas of address space,
365 * such as the start of vmalloc space etc.
366 * This helps in the interpretation.
367 */
368 if (addr >= st->marker[1].start_address) {
369 if (st->marker->max_lines &&
370 st->lines > st->marker->max_lines) {
371 unsigned long nskip =
372 st->lines - st->marker->max_lines;
373 pt_dump_seq_printf(m, st->to_dmesg,
374 "... %lu entr%s skipped ... \n",
375 nskip,
376 nskip == 1 ? "y" : "ies");
377 }
378 st->marker++;
379 st->lines = 0;
380 pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
381 st->marker->name);
382 }
383
384 st->start_address = addr;
385 st->current_prot = new_prot;
386 st->effective_prot = new_eff;
387 st->level = level;
388 }
389}
390
391static void note_page_pte(struct ptdump_state *pt_st, unsigned long addr, pte_t pte)
392{
393 note_page(pt_st, addr, level: 4, val: pte_val(pte));
394}
395
396static void note_page_pmd(struct ptdump_state *pt_st, unsigned long addr, pmd_t pmd)
397{
398 note_page(pt_st, addr, level: 3, val: pmd_val(pmd));
399}
400
401static void note_page_pud(struct ptdump_state *pt_st, unsigned long addr, pud_t pud)
402{
403 note_page(pt_st, addr, level: 2, val: pud_val(pud));
404}
405
406static void note_page_p4d(struct ptdump_state *pt_st, unsigned long addr, p4d_t p4d)
407{
408 note_page(pt_st, addr, level: 1, val: p4d_val(p4d));
409}
410
411static void note_page_pgd(struct ptdump_state *pt_st, unsigned long addr, pgd_t pgd)
412{
413 note_page(pt_st, addr, level: 0, val: pgd_val(pgd));
414}
415
416static void note_page_flush(struct ptdump_state *pt_st)
417{
418 pte_t pte_zero = {0};
419
420 note_page(pt_st, addr: 0, level: -1, val: pte_val(pte: pte_zero));
421}
422
423bool ptdump_walk_pgd_level_core(struct seq_file *m,
424 struct mm_struct *mm, pgd_t *pgd,
425 bool checkwx, bool dmesg)
426{
427 const struct ptdump_range ptdump_ranges[] = {
428#ifdef CONFIG_X86_64
429 {0, PTRS_PER_PGD * PGD_LEVEL_MULT / 2},
430 {GUARD_HOLE_END_ADDR, ~0UL},
431#else
432 {0, ~0UL},
433#endif
434 {0, 0}
435};
436
437 struct pg_state st = {
438 .ptdump = {
439 .note_page_pte = note_page_pte,
440 .note_page_pmd = note_page_pmd,
441 .note_page_pud = note_page_pud,
442 .note_page_p4d = note_page_p4d,
443 .note_page_pgd = note_page_pgd,
444 .note_page_flush = note_page_flush,
445 .effective_prot_pte = effective_prot_pte,
446 .effective_prot_pmd = effective_prot_pmd,
447 .effective_prot_pud = effective_prot_pud,
448 .effective_prot_p4d = effective_prot_p4d,
449 .effective_prot_pgd = effective_prot_pgd,
450 .range = ptdump_ranges
451 },
452 .level = -1,
453 .to_dmesg = dmesg,
454 .check_wx = checkwx,
455 .seq = m
456 };
457
458 ptdump_walk_pgd(st: &st.ptdump, mm, pgd);
459
460 if (!checkwx)
461 return true;
462 if (st.wx_pages) {
463 pr_info("x86/mm: Checked W+X mappings: FAILED, %lu W+X pages found.\n",
464 st.wx_pages);
465
466 return false;
467 } else {
468 pr_info("x86/mm: Checked W+X mappings: passed, no W+X pages found.\n");
469
470 return true;
471 }
472}
473
474void ptdump_walk_pgd_level(struct seq_file *m, struct mm_struct *mm)
475{
476 ptdump_walk_pgd_level_core(m, mm, pgd: mm->pgd, checkwx: false, dmesg: true);
477}
478
479void ptdump_walk_pgd_level_debugfs(struct seq_file *m, struct mm_struct *mm,
480 bool user)
481{
482 pgd_t *pgd = mm->pgd;
483#ifdef CONFIG_MITIGATION_PAGE_TABLE_ISOLATION
484 if (user && boot_cpu_has(X86_FEATURE_PTI))
485 pgd = kernel_to_user_pgdp(pgdp: pgd);
486#endif
487 ptdump_walk_pgd_level_core(m, mm, pgd, checkwx: false, dmesg: false);
488}
489
490void ptdump_walk_user_pgd_level_checkwx(void)
491{
492#ifdef CONFIG_MITIGATION_PAGE_TABLE_ISOLATION
493 pgd_t *pgd = INIT_PGD;
494
495 if (!(__supported_pte_mask & _PAGE_NX) ||
496 !boot_cpu_has(X86_FEATURE_PTI))
497 return;
498
499 pr_info("x86/mm: Checking user space page tables\n");
500 pgd = kernel_to_user_pgdp(pgdp: pgd);
501 ptdump_walk_pgd_level_core(NULL, mm: &init_mm, pgd, checkwx: true, dmesg: false);
502#endif
503}
504
505bool ptdump_walk_pgd_level_checkwx(void)
506{
507 if (!(__supported_pte_mask & _PAGE_NX))
508 return true;
509
510 return ptdump_walk_pgd_level_core(NULL, mm: &init_mm, INIT_PGD, checkwx: true, dmesg: false);
511}
512
513static int __init pt_dump_init(void)
514{
515 /*
516 * Various markers are not compile-time constants, so assign them
517 * here.
518 */
519#ifdef CONFIG_X86_64
520 address_markers[LOW_KERNEL_NR].start_address = PAGE_OFFSET;
521 address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
522 address_markers[VMEMMAP_START_NR].start_address = VMEMMAP_START;
523#ifdef CONFIG_MODIFY_LDT_SYSCALL
524 address_markers[LDT_NR].start_address = LDT_BASE_ADDR;
525#endif
526#ifdef CONFIG_KASAN
527 address_markers[KASAN_SHADOW_START_NR].start_address = KASAN_SHADOW_START;
528 address_markers[KASAN_SHADOW_END_NR].start_address = KASAN_SHADOW_END;
529#endif
530#endif
531#ifdef CONFIG_X86_32
532 address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
533 address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
534# ifdef CONFIG_HIGHMEM
535 address_markers[PKMAP_BASE_NR].start_address = PKMAP_BASE;
536# endif
537 address_markers[FIXADDR_START_NR].start_address = FIXADDR_START;
538 address_markers[CPU_ENTRY_AREA_NR].start_address = CPU_ENTRY_AREA_BASE;
539# ifdef CONFIG_MODIFY_LDT_SYSCALL
540 address_markers[LDT_NR].start_address = LDT_BASE_ADDR;
541# endif
542#endif
543 return 0;
544}
545__initcall(pt_dump_init);
546

source code of linux/arch/x86/mm/dump_pagetables.c