ptdump.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Copyright 2016, Rashmica Gupta, IBM Corp.
  4 *
  5 * This traverses the kernel pagetables and dumps the
  6 * information about the used sections of memory to
  7 * /sys/kernel/debug/kernel_pagetables.
  8 *
  9 * Derived from the arm64 implementation:
 10 * Copyright (c) 2014, The Linux Foundation, Laura Abbott.
 11 * (C) Copyright 2008 Intel Corporation, Arjan van de Ven.
 12 */
 13#include <linux/debugfs.h>
 14#include <linux/fs.h>
 15#include <linux/hugetlb.h>
 16#include <linux/io.h>
 17#include <linux/mm.h>
 18#include <linux/highmem.h>
 19#include <linux/ptdump.h>
 20#include <linux/sched.h>
 21#include <linux/seq_file.h>
 22#include <asm/fixmap.h>
 23#include <linux/const.h>
 24#include <linux/kasan.h>
 25#include <asm/page.h>
 26#include <asm/hugetlb.h>
 27
 28#include <mm/mmu_decl.h>
 29
 30#include "ptdump.h"
 31
 32/*
 33 * To visualise what is happening,
 34 *
 35 *  - PTRS_PER_P** = how many entries there are in the corresponding P**
 36 *  - P**_SHIFT = how many bits of the address we use to index into the
 37 * corresponding P**
 38 *  - P**_SIZE is how much memory we can access through the table - not the
 39 * size of the table itself.
 40 * P**={PGD, PUD, PMD, PTE}
 41 *
 42 *
 43 * Each entry of the PGD points to a PUD. Each entry of a PUD points to a
 44 * PMD. Each entry of a PMD points to a PTE. And every PTE entry points to
 45 * a page.
 46 *
 47 * In the case where there are only 3 levels, the PUD is folded into the
 48 * PGD: every PUD has only one entry which points to the PMD.
 49 *
 50 * The page dumper groups page table entries of the same type into a single
 51 * description. It uses pg_state to track the range information while
 52 * iterating over the PTE entries. When the continuity is broken it then
 53 * dumps out a description of the range - ie PTEs that are virtually contiguous
 54 * with the same PTE flags are chunked together. This is to make it clear how
 55 * different areas of the kernel virtual memory are used.
 56 *
 57 */
 58struct pg_state {
 59	struct ptdump_state ptdump;
 60	struct seq_file *seq;
 61	const struct addr_marker *marker;
 62	unsigned long start_address;
 63	unsigned long start_pa;
 64	int level;
 65	u64 current_flags;
 66	bool check_wx;
 67	unsigned long wx_pages;
 68};
 69
 70struct addr_marker {
 71	unsigned long start_address;
 72	const char *name;
 73};
 74
 75static struct addr_marker address_markers[] = {
 76	{ 0,	"Start of kernel VM" },
 77#ifdef MODULES_VADDR
 78	{ 0,	"modules start" },
 79	{ 0,	"modules end" },
 80#endif
 81	{ 0,	"vmalloc() Area" },
 82	{ 0,	"vmalloc() End" },
 83#ifdef CONFIG_PPC64
 84	{ 0,	"isa I/O start" },
 85	{ 0,	"isa I/O end" },
 86	{ 0,	"phb I/O start" },
 87	{ 0,	"phb I/O end" },
 88	{ 0,	"I/O remap start" },
 89	{ 0,	"I/O remap end" },
 90	{ 0,	"vmemmap start" },
 91#else
 92	{ 0,	"Early I/O remap start" },
 93	{ 0,	"Early I/O remap end" },
 94#ifdef CONFIG_HIGHMEM
 95	{ 0,	"Highmem PTEs start" },
 96	{ 0,	"Highmem PTEs end" },
 97#endif
 98	{ 0,	"Fixmap start" },
 99	{ 0,	"Fixmap end" },
100#endif
101#ifdef CONFIG_KASAN
102	{ 0,	"kasan shadow mem start" },
103	{ 0,	"kasan shadow mem end" },
104#endif
105	{ -1,	NULL },
106};
107
108static struct ptdump_range ptdump_range[] __ro_after_init = {
109	{TASK_SIZE_MAX, ~0UL},
110	{0, 0}
111};
112
113#define pt_dump_seq_printf(m, fmt, args...)	\
114({						\
115	if (m)					\
116		seq_printf(m, fmt, ##args);	\
117})
118
119#define pt_dump_seq_putc(m, c)		\
120({					\
121	if (m)				\
122		seq_putc(m, c);		\
123})
124
125void pt_dump_size(struct seq_file *m, unsigned long size)
126{
127	static const char units[] = " KMGTPE";
128	const char *unit = units;
129
130	/* Work out what appropriate unit to use */
131	while (!(size & 1023) && unit[1]) {
132		size >>= 10;
133		unit++;
134	}
135	pt_dump_seq_printf(m, "%9lu%c ", size, *unit);
136}
137
138static void dump_flag_info(struct pg_state *st, const struct flag_info
139		*flag, u64 pte, int num)
140{
141	unsigned int i;
142
143	for (i = 0; i < num; i++, flag++) {
144		const char *s = NULL;
145		u64 val;
146
147		/* flag not defined so don't check it */
148		if (flag->mask == 0)
149			continue;
150		/* Some 'flags' are actually values */
151		if (flag->is_val) {
152			val = pte & flag->val;
153			if (flag->shift)
154				val = val >> flag->shift;
155			pt_dump_seq_printf(st->seq, "  %s:%llx", flag->set, val);
156		} else {
157			if ((pte & flag->mask) == flag->val)
158				s = flag->set;
159			else
160				s = flag->clear;
161			if (s)
162				pt_dump_seq_printf(st->seq, "  %s", s);
163		}
164		st->current_flags &= ~flag->mask;
165	}
166	if (st->current_flags != 0)
167		pt_dump_seq_printf(st->seq, "  unknown flags:%llx", st->current_flags);
168}
169
170static void dump_addr(struct pg_state *st, unsigned long addr)
171{
172#ifdef CONFIG_PPC64
173#define REG		"0x%016lx"
174#else
175#define REG		"0x%08lx"
176#endif
177
178	pt_dump_seq_printf(st->seq, REG "-" REG " ", st->start_address, addr - 1);
179	pt_dump_seq_printf(st->seq, " " REG " ", st->start_pa);
180	pt_dump_size(st->seq, addr - st->start_address);
181	pt_dump_seq_printf(st->seq, "%s ", pg_level[st->level].name);
182}
183
184static void note_prot_wx(struct pg_state *st, unsigned long addr)
185{
186	pte_t pte = __pte(st->current_flags);
187
188	if (!st->check_wx)
189		return;
190
191	if (!pte_write(pte) || !pte_exec(pte))
192		return;
193
194	WARN_ONCE(IS_ENABLED(CONFIG_DEBUG_WX),
195		  "powerpc/mm: Found insecure W+X mapping at address %p/%pS\n",
196		  (void *)st->start_address, (void *)st->start_address);
197
198	st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
199}
200
201static void note_page_update_state(struct pg_state *st, unsigned long addr, int level, u64 val)
202{
203	u64 flag = level >= 0 ? val & pg_level[level].mask : 0;
204	u64 pa = val & PTE_RPN_MASK;
205
206	st->level = level;
207	st->current_flags = flag;
208	st->start_address = addr;
209	st->start_pa = pa;
210
211	while (addr >= st->marker[1].start_address) {
212		st->marker++;
213		pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
214	}
215}
216
217static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level, u64 val)
218{
219	u64 flag = level >= 0 ? val & pg_level[level].mask : 0;
220	struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
221
222	/* At first no level is set */
223	if (st->level == -1) {
224		pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
225		note_page_update_state(st, addr, level, val);
226	/*
227	 * Dump the section of virtual memory when:
228	 *   - the PTE flags from one entry to the next differs.
229	 *   - we change levels in the tree.
230	 *   - the address is in a different section of memory and is thus
231	 *   used for a different purpose, regardless of the flags.
232	 */
233	} else if (flag != st->current_flags || level != st->level ||
234		   addr >= st->marker[1].start_address) {
235
236		/* Check the PTE flags */
237		if (st->current_flags) {
238			note_prot_wx(st, addr);
239			dump_addr(st, addr);
240
241			/* Dump all the flags */
242			if (pg_level[st->level].flag)
243				dump_flag_info(st, pg_level[st->level].flag,
244					  st->current_flags,
245					  pg_level[st->level].num);
246
247			pt_dump_seq_putc(st->seq, '\n');
248		}
249
250		/*
251		 * Address indicates we have passed the end of the
252		 * current section of virtual memory
253		 */
254		note_page_update_state(st, addr, level, val);
255	}
256}
257
258static void populate_markers(void)
259{
260	int i = 0;
261
262#ifdef CONFIG_PPC64
263	address_markers[i++].start_address = PAGE_OFFSET;
264#else
265	address_markers[i++].start_address = TASK_SIZE;
266#endif
267#ifdef MODULES_VADDR
268	address_markers[i++].start_address = MODULES_VADDR;
269	address_markers[i++].start_address = MODULES_END;
270#endif
271	address_markers[i++].start_address = VMALLOC_START;
272	address_markers[i++].start_address = VMALLOC_END;
273#ifdef CONFIG_PPC64
274	address_markers[i++].start_address = ISA_IO_BASE;
275	address_markers[i++].start_address = ISA_IO_END;
276	address_markers[i++].start_address = PHB_IO_BASE;
277	address_markers[i++].start_address = PHB_IO_END;
278	address_markers[i++].start_address = IOREMAP_BASE;
279	address_markers[i++].start_address = IOREMAP_END;
280	/* What is the ifdef about? */
281#ifdef CONFIG_PPC_BOOK3S_64
282	address_markers[i++].start_address =  H_VMEMMAP_START;
283#else
284	address_markers[i++].start_address =  VMEMMAP_BASE;
285#endif
286#else /* !CONFIG_PPC64 */
287	address_markers[i++].start_address = ioremap_bot;
288	address_markers[i++].start_address = IOREMAP_TOP;
289#ifdef CONFIG_HIGHMEM
290	address_markers[i++].start_address = PKMAP_BASE;
291	address_markers[i++].start_address = PKMAP_ADDR(LAST_PKMAP);
292#endif
293	address_markers[i++].start_address = FIXADDR_START;
294	address_markers[i++].start_address = FIXADDR_TOP;
295#endif /* CONFIG_PPC64 */
296#ifdef CONFIG_KASAN
297	address_markers[i++].start_address = KASAN_SHADOW_START;
298	address_markers[i++].start_address = KASAN_SHADOW_END;
299#endif
300}
301
302static void note_page_pte(struct ptdump_state *pt_st, unsigned long addr, pte_t pte)
303{
304	note_page(pt_st, addr, 4, pte_val(pte));
305}
306
307static void note_page_pmd(struct ptdump_state *pt_st, unsigned long addr, pmd_t pmd)
308{
309	note_page(pt_st, addr, 3, pmd_val(pmd));
310}
311
312static void note_page_pud(struct ptdump_state *pt_st, unsigned long addr, pud_t pud)
313{
314	note_page(pt_st, addr, 2, pud_val(pud));
315}
316
317static void note_page_p4d(struct ptdump_state *pt_st, unsigned long addr, p4d_t p4d)
318{
319	note_page(pt_st, addr, 1, p4d_val(p4d));
320}
321
322static void note_page_pgd(struct ptdump_state *pt_st, unsigned long addr, pgd_t pgd)
323{
324	note_page(pt_st, addr, 0, pgd_val(pgd));
325}
326
327static void note_page_flush(struct ptdump_state *pt_st)
328{
329	pte_t pte_zero = {0};
330
331	note_page(pt_st, 0, -1, pte_val(pte_zero));
332}
333
334static int ptdump_show(struct seq_file *m, void *v)
335{
336	struct pg_state st = {
337		.seq = m,
338		.marker = address_markers,
339		.level = -1,
340		.ptdump = {
341			.note_page_pte = note_page_pte,
342			.note_page_pmd = note_page_pmd,
343			.note_page_pud = note_page_pud,
344			.note_page_p4d = note_page_p4d,
345			.note_page_pgd = note_page_pgd,
346			.note_page_flush = note_page_flush,
347			.range = ptdump_range,
348		}
349	};
350
351	/* Traverse kernel page tables */
352	ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
353	return 0;
354}
355
356DEFINE_SHOW_ATTRIBUTE(ptdump);
357
358static void __init build_pgtable_complete_mask(void)
359{
360	unsigned int i, j;
361
362	for (i = 0; i < ARRAY_SIZE(pg_level); i++)
363		if (pg_level[i].flag)
364			for (j = 0; j < pg_level[i].num; j++)
365				pg_level[i].mask |= pg_level[i].flag[j].mask;
366}
367
368bool ptdump_check_wx(void)
369{
370	struct pg_state st = {
371		.seq = NULL,
372		.marker = (struct addr_marker[]) {
373			{ 0, NULL},
374			{ -1, NULL},
375		},
376		.level = -1,
377		.check_wx = true,
378		.ptdump = {
379			.note_page_pte = note_page_pte,
380			.note_page_pmd = note_page_pmd,
381			.note_page_pud = note_page_pud,
382			.note_page_p4d = note_page_p4d,
383			.note_page_pgd = note_page_pgd,
384			.note_page_flush = note_page_flush,
385			.range = ptdump_range,
386		}
387	};
388
389	if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && !mmu_has_feature(MMU_FTR_KERNEL_RO))
390		return true;
391
392	ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
393
394	if (st.wx_pages) {
395		pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n",
396			st.wx_pages);
397
398		return false;
399	} else {
400		pr_info("Checked W+X mappings: passed, no W+X pages found\n");
401
402		return true;
403	}
404}
405
406static int __init ptdump_init(void)
407{
408#ifdef CONFIG_PPC64
409	if (!radix_enabled())
410		ptdump_range[0].start = KERN_VIRT_START;
411	else
412		ptdump_range[0].start = PAGE_OFFSET;
413
414	ptdump_range[0].end = PAGE_OFFSET + (PGDIR_SIZE * PTRS_PER_PGD);
415#endif
416
417	populate_markers();
418	build_pgtable_complete_mask();
419
420	if (IS_ENABLED(CONFIG_PTDUMP_DEBUGFS))
421		debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops);
422
423	return 0;
424}
425device_initcall(ptdump_init);