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}
182
183static void note_prot_wx(struct pg_state *st, unsigned long addr)
184{
185	pte_t pte = __pte(st->current_flags);
186
187	if (!IS_ENABLED(CONFIG_DEBUG_WX) || !st->check_wx)
188		return;
189
190	if (!pte_write(pte) || !pte_exec(pte))
191		return;
192
193	WARN_ONCE(1, "powerpc/mm: Found insecure W+X mapping at address %p/%pS\n",
194		  (void *)st->start_address, (void *)st->start_address);
195
196	st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
197}
198
199static void note_page_update_state(struct pg_state *st, unsigned long addr, int level, u64 val)
200{
201	u64 flag = level >= 0 ? val & pg_level[level].mask : 0;
202	u64 pa = val & PTE_RPN_MASK;
203
204	st->level = level;
205	st->current_flags = flag;
206	st->start_address = addr;
207	st->start_pa = pa;
208
209	while (addr >= st->marker[1].start_address) {
210		st->marker++;
211		pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
212	}
213}
214
215static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level, u64 val)
216{
217	u64 flag = level >= 0 ? val & pg_level[level].mask : 0;
218	struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
219
220	/* At first no level is set */
221	if (st->level == -1) {
222		pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
223		note_page_update_state(st, addr, level, val);
224	/*
225	 * Dump the section of virtual memory when:
226	 *   - the PTE flags from one entry to the next differs.
227	 *   - we change levels in the tree.
228	 *   - the address is in a different section of memory and is thus
229	 *   used for a different purpose, regardless of the flags.
230	 */
231	} else if (flag != st->current_flags || level != st->level ||
232		   addr >= st->marker[1].start_address) {
233
234		/* Check the PTE flags */
235		if (st->current_flags) {
236			note_prot_wx(st, addr);
237			dump_addr(st, addr);
238
239			/* Dump all the flags */
240			if (pg_level[st->level].flag)
241				dump_flag_info(st, pg_level[st->level].flag,
242					  st->current_flags,
243					  pg_level[st->level].num);
244
245			pt_dump_seq_putc(st->seq, '\n');
246		}
247
248		/*
249		 * Address indicates we have passed the end of the
250		 * current section of virtual memory
251		 */
252		note_page_update_state(st, addr, level, val);
253	}
254}
255
256static void populate_markers(void)
257{
258	int i = 0;
259
260#ifdef CONFIG_PPC64
261	address_markers[i++].start_address = PAGE_OFFSET;
262#else
263	address_markers[i++].start_address = TASK_SIZE;
264#endif
265#ifdef MODULES_VADDR
266	address_markers[i++].start_address = MODULES_VADDR;
267	address_markers[i++].start_address = MODULES_END;
268#endif
269	address_markers[i++].start_address = VMALLOC_START;
270	address_markers[i++].start_address = VMALLOC_END;
271#ifdef CONFIG_PPC64
272	address_markers[i++].start_address = ISA_IO_BASE;
273	address_markers[i++].start_address = ISA_IO_END;
274	address_markers[i++].start_address = PHB_IO_BASE;
275	address_markers[i++].start_address = PHB_IO_END;
276	address_markers[i++].start_address = IOREMAP_BASE;
277	address_markers[i++].start_address = IOREMAP_END;
278	/* What is the ifdef about? */
279#ifdef CONFIG_PPC_BOOK3S_64
280	address_markers[i++].start_address =  H_VMEMMAP_START;
281#else
282	address_markers[i++].start_address =  VMEMMAP_BASE;
283#endif
284#else /* !CONFIG_PPC64 */
285	address_markers[i++].start_address = ioremap_bot;
286	address_markers[i++].start_address = IOREMAP_TOP;
287#ifdef CONFIG_HIGHMEM
288	address_markers[i++].start_address = PKMAP_BASE;
289	address_markers[i++].start_address = PKMAP_ADDR(LAST_PKMAP);
290#endif
291	address_markers[i++].start_address = FIXADDR_START;
292	address_markers[i++].start_address = FIXADDR_TOP;
293#endif /* CONFIG_PPC64 */
294#ifdef CONFIG_KASAN
295	address_markers[i++].start_address = KASAN_SHADOW_START;
296	address_markers[i++].start_address = KASAN_SHADOW_END;
297#endif
298}
299
300static int ptdump_show(struct seq_file *m, void *v)
301{
302	struct pg_state st = {
303		.seq = m,
304		.marker = address_markers,
305		.level = -1,
306		.ptdump = {
307			.note_page = note_page,
308			.range = ptdump_range,
309		}
310	};
311
312	/* Traverse kernel page tables */
313	ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
314	return 0;
315}
316
317DEFINE_SHOW_ATTRIBUTE(ptdump);
318
319static void __init build_pgtable_complete_mask(void)
320{
321	unsigned int i, j;
322
323	for (i = 0; i < ARRAY_SIZE(pg_level); i++)
324		if (pg_level[i].flag)
325			for (j = 0; j < pg_level[i].num; j++)
326				pg_level[i].mask |= pg_level[i].flag[j].mask;
327}
328
329#ifdef CONFIG_DEBUG_WX
330void ptdump_check_wx(void)
331{
332	struct pg_state st = {
333		.seq = NULL,
334		.marker = (struct addr_marker[]) {
335			{ 0, NULL},
336			{ -1, NULL},
337		},
338		.level = -1,
339		.check_wx = true,
340		.ptdump = {
341			.note_page = note_page,
342			.range = ptdump_range,
343		}
344	};
345
346	ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
347
348	if (st.wx_pages)
349		pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n",
350			st.wx_pages);
351	else
352		pr_info("Checked W+X mappings: passed, no W+X pages found\n");
353}
354#endif
355
356static int __init ptdump_init(void)
357{
358#ifdef CONFIG_PPC64
359	if (!radix_enabled())
360		ptdump_range[0].start = KERN_VIRT_START;
361	else
362		ptdump_range[0].start = PAGE_OFFSET;
363
364	ptdump_range[0].end = PAGE_OFFSET + (PGDIR_SIZE * PTRS_PER_PGD);
365#endif
366
367	populate_markers();
368	build_pgtable_complete_mask();
369
370	if (IS_ENABLED(CONFIG_PTDUMP_DEBUGFS))
371		debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops);
372
373	return 0;
374}
375device_initcall(ptdump_init);
376