xref: /openbmc/linux/arch/x86/mm/dump_pagetables.c (revision 4f139972b489f8bc2c821aa25ac65018d92af3f7) 
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  */
29 struct 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 
41 struct 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 */
48 enum 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 */
77 static 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 PGD_LEVEL_MULT (PTRS_PER_PUD * PUD_LEVEL_MULT)
114 
115 #define pt_dump_seq_printf(m, to_dmesg, fmt, args...)		\
116 ({								\
117 	if (to_dmesg)					\
118 		printk(KERN_INFO fmt, ##args);			\
119 	else							\
120 		if (m)						\
121 			seq_printf(m, fmt, ##args);		\
122 })
123 
124 #define pt_dump_cont_printf(m, to_dmesg, fmt, args...)		\
125 ({								\
126 	if (to_dmesg)					\
127 		printk(KERN_CONT fmt, ##args);			\
128 	else							\
129 		if (m)						\
130 			seq_printf(m, fmt, ##args);		\
131 })
132 
133 /*
134  * Print a readable form of a pgprot_t to the seq_file
135  */
136 static void printk_prot(struct seq_file *m, pgprot_t prot, int level, bool dmsg)
137 {
138 	pgprotval_t pr = pgprot_val(prot);
139 	static const char * const level_name[] =
140 		{ "cr3", "pgd", "pud", "pmd", "pte" };
141 
142 	if (!pgprot_val(prot)) {
143 		/* Not present */
144 		pt_dump_cont_printf(m, dmsg, "                              ");
145 	} else {
146 		if (pr & _PAGE_USER)
147 			pt_dump_cont_printf(m, dmsg, "USR ");
148 		else
149 			pt_dump_cont_printf(m, dmsg, "    ");
150 		if (pr & _PAGE_RW)
151 			pt_dump_cont_printf(m, dmsg, "RW ");
152 		else
153 			pt_dump_cont_printf(m, dmsg, "ro ");
154 		if (pr & _PAGE_PWT)
155 			pt_dump_cont_printf(m, dmsg, "PWT ");
156 		else
157 			pt_dump_cont_printf(m, dmsg, "    ");
158 		if (pr & _PAGE_PCD)
159 			pt_dump_cont_printf(m, dmsg, "PCD ");
160 		else
161 			pt_dump_cont_printf(m, dmsg, "    ");
162 
163 		/* Bit 7 has a different meaning on level 3 vs 4 */
164 		if (level <= 3 && pr & _PAGE_PSE)
165 			pt_dump_cont_printf(m, dmsg, "PSE ");
166 		else
167 			pt_dump_cont_printf(m, dmsg, "    ");
168 		if ((level == 4 && pr & _PAGE_PAT) ||
169 		    ((level == 3 || level == 2) && pr & _PAGE_PAT_LARGE))
170 			pt_dump_cont_printf(m, dmsg, "PAT ");
171 		else
172 			pt_dump_cont_printf(m, dmsg, "    ");
173 		if (pr & _PAGE_GLOBAL)
174 			pt_dump_cont_printf(m, dmsg, "GLB ");
175 		else
176 			pt_dump_cont_printf(m, dmsg, "    ");
177 		if (pr & _PAGE_NX)
178 			pt_dump_cont_printf(m, dmsg, "NX ");
179 		else
180 			pt_dump_cont_printf(m, dmsg, "x  ");
181 	}
182 	pt_dump_cont_printf(m, dmsg, "%s\n", level_name[level]);
183 }
184 
185 /*
186  * On 64 bits, sign-extend the 48 bit address to 64 bit
187  */
188 static unsigned long normalize_addr(unsigned long u)
189 {
190 #ifdef CONFIG_X86_64
191 	return (signed long)(u << 16) >> 16;
192 #else
193 	return u;
194 #endif
195 }
196 
197 /*
198  * This function gets called on a break in a continuous series
199  * of PTE entries; the next one is different so we need to
200  * print what we collected so far.
201  */
202 static void note_page(struct seq_file *m, struct pg_state *st,
203 		      pgprot_t new_prot, int level)
204 {
205 	pgprotval_t prot, cur;
206 	static const char units[] = "BKMGTPE";
207 
208 	/*
209 	 * If we have a "break" in the series, we need to flush the state that
210 	 * we have now. "break" is either changing perms, levels or
211 	 * address space marker.
212 	 */
213 	prot = pgprot_val(new_prot);
214 	cur = pgprot_val(st->current_prot);
215 
216 	if (!st->level) {
217 		/* First entry */
218 		st->current_prot = new_prot;
219 		st->level = level;
220 		st->marker = address_markers;
221 		st->lines = 0;
222 		pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
223 				   st->marker->name);
224 	} else if (prot != cur || level != st->level ||
225 		   st->current_address >= st->marker[1].start_address) {
226 		const char *unit = units;
227 		unsigned long delta;
228 		int width = sizeof(unsigned long) * 2;
229 		pgprotval_t pr = pgprot_val(st->current_prot);
230 
231 		if (st->check_wx && (pr & _PAGE_RW) && !(pr & _PAGE_NX)) {
232 			WARN_ONCE(1,
233 				  "x86/mm: Found insecure W+X mapping at address %p/%pS\n",
234 				  (void *)st->start_address,
235 				  (void *)st->start_address);
236 			st->wx_pages += (st->current_address -
237 					 st->start_address) / PAGE_SIZE;
238 		}
239 
240 		/*
241 		 * Now print the actual finished series
242 		 */
243 		if (!st->marker->max_lines ||
244 		    st->lines < st->marker->max_lines) {
245 			pt_dump_seq_printf(m, st->to_dmesg,
246 					   "0x%0*lx-0x%0*lx   ",
247 					   width, st->start_address,
248 					   width, st->current_address);
249 
250 			delta = st->current_address - st->start_address;
251 			while (!(delta & 1023) && unit[1]) {
252 				delta >>= 10;
253 				unit++;
254 			}
255 			pt_dump_cont_printf(m, st->to_dmesg, "%9lu%c ",
256 					    delta, *unit);
257 			printk_prot(m, st->current_prot, st->level,
258 				    st->to_dmesg);
259 		}
260 		st->lines++;
261 
262 		/*
263 		 * We print markers for special areas of address space,
264 		 * such as the start of vmalloc space etc.
265 		 * This helps in the interpretation.
266 		 */
267 		if (st->current_address >= st->marker[1].start_address) {
268 			if (st->marker->max_lines &&
269 			    st->lines > st->marker->max_lines) {
270 				unsigned long nskip =
271 					st->lines - st->marker->max_lines;
272 				pt_dump_seq_printf(m, st->to_dmesg,
273 						   "... %lu entr%s skipped ... \n",
274 						   nskip,
275 						   nskip == 1 ? "y" : "ies");
276 			}
277 			st->marker++;
278 			st->lines = 0;
279 			pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
280 					   st->marker->name);
281 		}
282 
283 		st->start_address = st->current_address;
284 		st->current_prot = new_prot;
285 		st->level = level;
286 	}
287 }
288 
289 static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr,
290 							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 
307 static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr,
308 							unsigned long P)
309 {
310 	int i;
311 	pmd_t *start;
312 	pgprotval_t prot;
313 
314 	start = (pmd_t *) pud_page_vaddr(addr);
315 	for (i = 0; i < PTRS_PER_PMD; i++) {
316 		st->current_address = normalize_addr(P + i * PMD_LEVEL_MULT);
317 		if (!pmd_none(*start)) {
318 			if (pmd_large(*start) || !pmd_present(*start)) {
319 				prot = pmd_flags(*start);
320 				note_page(m, st, __pgprot(prot), 3);
321 			} else {
322 				walk_pte_level(m, st, *start,
323 					       P + i * PMD_LEVEL_MULT);
324 			}
325 		} else
326 			note_page(m, st, __pgprot(0), 3);
327 		start++;
328 	}
329 }
330 
331 #else
332 #define walk_pmd_level(m,s,a,p) walk_pte_level(m,s,__pmd(pud_val(a)),p)
333 #define pud_large(a) pmd_large(__pmd(pud_val(a)))
334 #define pud_none(a)  pmd_none(__pmd(pud_val(a)))
335 #endif
336 
337 #if PTRS_PER_PUD > 1
338 
339 /*
340  * This is an optimization for CONFIG_DEBUG_WX=y + CONFIG_KASAN=y
341  * KASAN fills page tables with the same values. Since there is no
342  * point in checking page table more than once we just skip repeated
343  * entries. This saves us dozens of seconds during boot.
344  */
345 static bool pud_already_checked(pud_t *prev_pud, pud_t *pud, bool checkwx)
346 {
347 	return checkwx && prev_pud && (pud_val(*prev_pud) == pud_val(*pud));
348 }
349 
350 static void walk_pud_level(struct seq_file *m, struct pg_state *st, pgd_t addr,
351 							unsigned long P)
352 {
353 	int i;
354 	pud_t *start;
355 	pgprotval_t prot;
356 	pud_t *prev_pud = NULL;
357 
358 	start = (pud_t *) pgd_page_vaddr(addr);
359 
360 	for (i = 0; i < PTRS_PER_PUD; i++) {
361 		st->current_address = normalize_addr(P + i * PUD_LEVEL_MULT);
362 		if (!pud_none(*start) &&
363 		    !pud_already_checked(prev_pud, start, st->check_wx)) {
364 			if (pud_large(*start) || !pud_present(*start)) {
365 				prot = pud_flags(*start);
366 				note_page(m, st, __pgprot(prot), 2);
367 			} else {
368 				walk_pmd_level(m, st, *start,
369 					       P + i * PUD_LEVEL_MULT);
370 			}
371 		} else
372 			note_page(m, st, __pgprot(0), 2);
373 
374 		prev_pud = start;
375 		start++;
376 	}
377 }
378 
379 #else
380 #define walk_pud_level(m,s,a,p) walk_pmd_level(m,s,__pud(pgd_val(a)),p)
381 #define pgd_large(a) pud_large(__pud(pgd_val(a)))
382 #define pgd_none(a)  pud_none(__pud(pgd_val(a)))
383 #endif
384 
385 static inline bool is_hypervisor_range(int idx)
386 {
387 #ifdef CONFIG_X86_64
388 	/*
389 	 * ffff800000000000 - ffff87ffffffffff is reserved for
390 	 * the hypervisor.
391 	 */
392 	return	(idx >= pgd_index(__PAGE_OFFSET) - 16) &&
393 		(idx <  pgd_index(__PAGE_OFFSET));
394 #else
395 	return false;
396 #endif
397 }
398 
399 static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
400 				       bool checkwx)
401 {
402 #ifdef CONFIG_X86_64
403 	pgd_t *start = (pgd_t *) &init_level4_pgt;
404 #else
405 	pgd_t *start = swapper_pg_dir;
406 #endif
407 	pgprotval_t prot;
408 	int i;
409 	struct pg_state st = {};
410 
411 	if (pgd) {
412 		start = pgd;
413 		st.to_dmesg = true;
414 	}
415 
416 	st.check_wx = checkwx;
417 	if (checkwx)
418 		st.wx_pages = 0;
419 
420 	for (i = 0; i < PTRS_PER_PGD; i++) {
421 		st.current_address = normalize_addr(i * PGD_LEVEL_MULT);
422 		if (!pgd_none(*start) && !is_hypervisor_range(i)) {
423 			if (pgd_large(*start) || !pgd_present(*start)) {
424 				prot = pgd_flags(*start);
425 				note_page(m, &st, __pgprot(prot), 1);
426 			} else {
427 				walk_pud_level(m, &st, *start,
428 					       i * PGD_LEVEL_MULT);
429 			}
430 		} else
431 			note_page(m, &st, __pgprot(0), 1);
432 
433 		cond_resched();
434 		start++;
435 	}
436 
437 	/* Flush out the last page */
438 	st.current_address = normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT);
439 	note_page(m, &st, __pgprot(0), 0);
440 	if (!checkwx)
441 		return;
442 	if (st.wx_pages)
443 		pr_info("x86/mm: Checked W+X mappings: FAILED, %lu W+X pages found.\n",
444 			st.wx_pages);
445 	else
446 		pr_info("x86/mm: Checked W+X mappings: passed, no W+X pages found.\n");
447 }
448 
449 void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd)
450 {
451 	ptdump_walk_pgd_level_core(m, pgd, false);
452 }
453 EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level);
454 
455 void ptdump_walk_pgd_level_checkwx(void)
456 {
457 	ptdump_walk_pgd_level_core(NULL, NULL, true);
458 }
459 
460 static int __init pt_dump_init(void)
461 {
462 	/*
463 	 * Various markers are not compile-time constants, so assign them
464 	 * here.
465 	 */
466 #ifdef CONFIG_X86_64
467 	address_markers[LOW_KERNEL_NR].start_address = PAGE_OFFSET;
468 	address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
469 	address_markers[VMEMMAP_START_NR].start_address = VMEMMAP_START;
470 #endif
471 #ifdef CONFIG_X86_32
472 	address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
473 	address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
474 # ifdef CONFIG_HIGHMEM
475 	address_markers[PKMAP_BASE_NR].start_address = PKMAP_BASE;
476 # endif
477 	address_markers[FIXADDR_START_NR].start_address = FIXADDR_START;
478 #endif
479 
480 	return 0;
481 }
482 __initcall(pt_dump_init);
483