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 */
28 struct 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
43 struct 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
53 enum 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
80 static 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
115 enum 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
131 static 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 */
printk_prot(struct seq_file * m,pgprotval_t pr,int level,bool dmsg)179 static 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
note_wx(struct pg_state * st,unsigned long addr)227 static 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
effective_prot(struct ptdump_state * pt_st,int level,u64 val)251 static 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
269 /*
270 * This function gets called on a break in a continuous series
271 * of PTE entries; the next one is different so we need to
272 * print what we collected so far.
273 */
note_page(struct ptdump_state * pt_st,unsigned long addr,int level,u64 val)274 static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
275 u64 val)
276 {
277 struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
278 pgprotval_t new_prot, new_eff;
279 pgprotval_t cur, eff;
280 static const char units[] = "BKMGTPE";
281 struct seq_file *m = st->seq;
282
283 new_prot = val & PTE_FLAGS_MASK;
284 if (!val)
285 new_eff = 0;
286 else
287 new_eff = st->prot_levels[level];
288
289 /*
290 * If we have a "break" in the series, we need to flush the state that
291 * we have now. "break" is either changing perms, levels or
292 * address space marker.
293 */
294 cur = st->current_prot;
295 eff = st->effective_prot;
296
297 if (st->level == -1) {
298 /* First entry */
299 st->current_prot = new_prot;
300 st->effective_prot = new_eff;
301 st->level = level;
302 st->marker = address_markers;
303 st->lines = 0;
304 pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
305 st->marker->name);
306 } else if (new_prot != cur || new_eff != eff || level != st->level ||
307 addr >= st->marker[1].start_address) {
308 const char *unit = units;
309 unsigned long delta;
310 int width = sizeof(unsigned long) * 2;
311
312 if (st->check_wx && (eff & _PAGE_RW) && !(eff & _PAGE_NX))
313 note_wx(st, addr);
314
315 /*
316 * Now print the actual finished series
317 */
318 if (!st->marker->max_lines ||
319 st->lines < st->marker->max_lines) {
320 pt_dump_seq_printf(m, st->to_dmesg,
321 "0x%0*lx-0x%0*lx ",
322 width, st->start_address,
323 width, addr);
324
325 delta = addr - st->start_address;
326 while (!(delta & 1023) && unit[1]) {
327 delta >>= 10;
328 unit++;
329 }
330 pt_dump_cont_printf(m, st->to_dmesg, "%9lu%c ",
331 delta, *unit);
332 printk_prot(m, st->current_prot, st->level,
333 st->to_dmesg);
334 }
335 st->lines++;
336
337 /*
338 * We print markers for special areas of address space,
339 * such as the start of vmalloc space etc.
340 * This helps in the interpretation.
341 */
342 if (addr >= st->marker[1].start_address) {
343 if (st->marker->max_lines &&
344 st->lines > st->marker->max_lines) {
345 unsigned long nskip =
346 st->lines - st->marker->max_lines;
347 pt_dump_seq_printf(m, st->to_dmesg,
348 "... %lu entr%s skipped ... \n",
349 nskip,
350 nskip == 1 ? "y" : "ies");
351 }
352 st->marker++;
353 st->lines = 0;
354 pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
355 st->marker->name);
356 }
357
358 st->start_address = addr;
359 st->current_prot = new_prot;
360 st->effective_prot = new_eff;
361 st->level = level;
362 }
363 }
364
ptdump_walk_pgd_level_core(struct seq_file * m,struct mm_struct * mm,pgd_t * pgd,bool checkwx,bool dmesg)365 bool ptdump_walk_pgd_level_core(struct seq_file *m,
366 struct mm_struct *mm, pgd_t *pgd,
367 bool checkwx, bool dmesg)
368 {
369 const struct ptdump_range ptdump_ranges[] = {
370 #ifdef CONFIG_X86_64
371 {0, PTRS_PER_PGD * PGD_LEVEL_MULT / 2},
372 {GUARD_HOLE_END_ADDR, ~0UL},
373 #else
374 {0, ~0UL},
375 #endif
376 {0, 0}
377 };
378
379 struct pg_state st = {
380 .ptdump = {
381 .note_page = note_page,
382 .effective_prot = effective_prot,
383 .range = ptdump_ranges
384 },
385 .level = -1,
386 .to_dmesg = dmesg,
387 .check_wx = checkwx,
388 .seq = m
389 };
390
391 ptdump_walk_pgd(&st.ptdump, mm, pgd);
392
393 if (!checkwx)
394 return true;
395 if (st.wx_pages) {
396 pr_info("x86/mm: Checked W+X mappings: FAILED, %lu W+X pages found.\n",
397 st.wx_pages);
398
399 return false;
400 } else {
401 pr_info("x86/mm: Checked W+X mappings: passed, no W+X pages found.\n");
402
403 return true;
404 }
405 }
406
ptdump_walk_pgd_level(struct seq_file * m,struct mm_struct * mm)407 void ptdump_walk_pgd_level(struct seq_file *m, struct mm_struct *mm)
408 {
409 ptdump_walk_pgd_level_core(m, mm, mm->pgd, false, true);
410 }
411
ptdump_walk_pgd_level_debugfs(struct seq_file * m,struct mm_struct * mm,bool user)412 void ptdump_walk_pgd_level_debugfs(struct seq_file *m, struct mm_struct *mm,
413 bool user)
414 {
415 pgd_t *pgd = mm->pgd;
416 #ifdef CONFIG_MITIGATION_PAGE_TABLE_ISOLATION
417 if (user && boot_cpu_has(X86_FEATURE_PTI))
418 pgd = kernel_to_user_pgdp(pgd);
419 #endif
420 ptdump_walk_pgd_level_core(m, mm, pgd, false, false);
421 }
422 EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level_debugfs);
423
ptdump_walk_user_pgd_level_checkwx(void)424 void ptdump_walk_user_pgd_level_checkwx(void)
425 {
426 #ifdef CONFIG_MITIGATION_PAGE_TABLE_ISOLATION
427 pgd_t *pgd = INIT_PGD;
428
429 if (!(__supported_pte_mask & _PAGE_NX) ||
430 !boot_cpu_has(X86_FEATURE_PTI))
431 return;
432
433 pr_info("x86/mm: Checking user space page tables\n");
434 pgd = kernel_to_user_pgdp(pgd);
435 ptdump_walk_pgd_level_core(NULL, &init_mm, pgd, true, false);
436 #endif
437 }
438
ptdump_walk_pgd_level_checkwx(void)439 bool ptdump_walk_pgd_level_checkwx(void)
440 {
441 if (!(__supported_pte_mask & _PAGE_NX))
442 return true;
443
444 return ptdump_walk_pgd_level_core(NULL, &init_mm, INIT_PGD, true, false);
445 }
446
pt_dump_init(void)447 static int __init pt_dump_init(void)
448 {
449 /*
450 * Various markers are not compile-time constants, so assign them
451 * here.
452 */
453 #ifdef CONFIG_X86_64
454 address_markers[LOW_KERNEL_NR].start_address = PAGE_OFFSET;
455 address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
456 address_markers[VMEMMAP_START_NR].start_address = VMEMMAP_START;
457 #ifdef CONFIG_MODIFY_LDT_SYSCALL
458 address_markers[LDT_NR].start_address = LDT_BASE_ADDR;
459 #endif
460 #ifdef CONFIG_KASAN
461 address_markers[KASAN_SHADOW_START_NR].start_address = KASAN_SHADOW_START;
462 address_markers[KASAN_SHADOW_END_NR].start_address = KASAN_SHADOW_END;
463 #endif
464 #endif
465 #ifdef CONFIG_X86_32
466 address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
467 address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
468 # ifdef CONFIG_HIGHMEM
469 address_markers[PKMAP_BASE_NR].start_address = PKMAP_BASE;
470 # endif
471 address_markers[FIXADDR_START_NR].start_address = FIXADDR_START;
472 address_markers[CPU_ENTRY_AREA_NR].start_address = CPU_ENTRY_AREA_BASE;
473 # ifdef CONFIG_MODIFY_LDT_SYSCALL
474 address_markers[LDT_NR].start_address = LDT_BASE_ADDR;
475 # endif
476 #endif
477 return 0;
478 }
479 __initcall(pt_dump_init);
480