1// SPDX-License-Identifier: GPL-2.0
2#include <linux/set_memory.h>
3#include <linux/ptdump.h>
4#include <linux/seq_file.h>
5#include <linux/debugfs.h>
6#include <linux/mm.h>
7#include <linux/kfence.h>
8#include <linux/kasan.h>
9#include <asm/kasan.h>
10#include <asm/abs_lowcore.h>
11#include <asm/nospec-branch.h>
12#include <asm/sections.h>
13#include <asm/maccess.h>
14
15static unsigned long max_addr;
16
17struct addr_marker {
18	unsigned long start_address;
19	const char *name;
20};
21
22enum address_markers_idx {
23	IDENTITY_BEFORE_NR = 0,
24	IDENTITY_BEFORE_END_NR,
25	AMODE31_START_NR,
26	AMODE31_END_NR,
27	KERNEL_START_NR,
28	KERNEL_END_NR,
29#ifdef CONFIG_KFENCE
30	KFENCE_START_NR,
31	KFENCE_END_NR,
32#endif
33	IDENTITY_AFTER_NR,
34	IDENTITY_AFTER_END_NR,
35	VMEMMAP_NR,
36	VMEMMAP_END_NR,
37	VMALLOC_NR,
38	VMALLOC_END_NR,
39	MODULES_NR,
40	MODULES_END_NR,
41	ABS_LOWCORE_NR,
42	ABS_LOWCORE_END_NR,
43	MEMCPY_REAL_NR,
44	MEMCPY_REAL_END_NR,
45#ifdef CONFIG_KASAN
46	KASAN_SHADOW_START_NR,
47	KASAN_SHADOW_END_NR,
48#endif
49};
50
51static struct addr_marker address_markers[] = {
52	[IDENTITY_BEFORE_NR]	= {0, "Identity Mapping Start"},
53	[IDENTITY_BEFORE_END_NR] = {(unsigned long)_stext, "Identity Mapping End"},
54	[AMODE31_START_NR]	= {0, "Amode31 Area Start"},
55	[AMODE31_END_NR]	= {0, "Amode31 Area End"},
56	[KERNEL_START_NR]	= {(unsigned long)_stext, "Kernel Image Start"},
57	[KERNEL_END_NR]		= {(unsigned long)_end, "Kernel Image End"},
58#ifdef CONFIG_KFENCE
59	[KFENCE_START_NR]	= {0, "KFence Pool Start"},
60	[KFENCE_END_NR]		= {0, "KFence Pool End"},
61#endif
62	[IDENTITY_AFTER_NR]	= {(unsigned long)_end, "Identity Mapping Start"},
63	[IDENTITY_AFTER_END_NR]	= {0, "Identity Mapping End"},
64	[VMEMMAP_NR]		= {0, "vmemmap Area Start"},
65	[VMEMMAP_END_NR]	= {0, "vmemmap Area End"},
66	[VMALLOC_NR]		= {0, "vmalloc Area Start"},
67	[VMALLOC_END_NR]	= {0, "vmalloc Area End"},
68	[MODULES_NR]		= {0, "Modules Area Start"},
69	[MODULES_END_NR]	= {0, "Modules Area End"},
70	[ABS_LOWCORE_NR]	= {0, "Lowcore Area Start"},
71	[ABS_LOWCORE_END_NR]	= {0, "Lowcore Area End"},
72	[MEMCPY_REAL_NR]	= {0, "Real Memory Copy Area Start"},
73	[MEMCPY_REAL_END_NR]	= {0, "Real Memory Copy Area End"},
74#ifdef CONFIG_KASAN
75	[KASAN_SHADOW_START_NR]	= {KASAN_SHADOW_START, "Kasan Shadow Start"},
76	[KASAN_SHADOW_END_NR]	= {KASAN_SHADOW_END, "Kasan Shadow End"},
77#endif
78	{ -1, NULL }
79};
80
81struct pg_state {
82	struct ptdump_state ptdump;
83	struct seq_file *seq;
84	int level;
85	unsigned int current_prot;
86	bool check_wx;
87	unsigned long wx_pages;
88	unsigned long start_address;
89	const struct addr_marker *marker;
90};
91
92#define pt_dump_seq_printf(m, fmt, args...)	\
93({						\
94	struct seq_file *__m = (m);		\
95						\
96	if (__m)				\
97		seq_printf(__m, fmt, ##args);	\
98})
99
100#define pt_dump_seq_puts(m, fmt)		\
101({						\
102	struct seq_file *__m = (m);		\
103						\
104	if (__m)				\
105		seq_printf(__m, fmt);		\
106})
107
108static void print_prot(struct seq_file *m, unsigned int pr, int level)
109{
110	static const char * const level_name[] =
111		{ "ASCE", "PGD", "PUD", "PMD", "PTE" };
112
113	pt_dump_seq_printf(m, "%s ", level_name[level]);
114	if (pr & _PAGE_INVALID) {
115		pt_dump_seq_printf(m, "I\n");
116		return;
117	}
118	pt_dump_seq_puts(m, (pr & _PAGE_PROTECT) ? "RO " : "RW ");
119	pt_dump_seq_puts(m, (pr & _PAGE_NOEXEC) ? "NX\n" : "X\n");
120}
121
122static void note_prot_wx(struct pg_state *st, unsigned long addr)
123{
124	if (!st->check_wx)
125		return;
126	if (st->current_prot & _PAGE_INVALID)
127		return;
128	if (st->current_prot & _PAGE_PROTECT)
129		return;
130	if (st->current_prot & _PAGE_NOEXEC)
131		return;
132	/*
133	 * The first lowcore page is W+X if spectre mitigations are using
134	 * trampolines or the BEAR enhancements facility is not installed,
135	 * in which case we have two lpswe instructions in lowcore that need
136	 * to be executable.
137	 */
138	if (addr == PAGE_SIZE && (nospec_uses_trampoline() || !static_key_enabled(&cpu_has_bear)))
139		return;
140	WARN_ONCE(IS_ENABLED(CONFIG_DEBUG_WX),
141		  "s390/mm: Found insecure W+X mapping at address %pS\n",
142		  (void *)st->start_address);
143	st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
144}
145
146static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level, u64 val)
147{
148	int width = sizeof(unsigned long) * 2;
149	static const char units[] = "KMGTPE";
150	const char *unit = units;
151	unsigned long delta;
152	struct pg_state *st;
153	struct seq_file *m;
154	unsigned int prot;
155
156	st = container_of(pt_st, struct pg_state, ptdump);
157	m = st->seq;
158	prot = val & (_PAGE_PROTECT | _PAGE_NOEXEC);
159	if (level == 4 && (val & _PAGE_INVALID))
160		prot = _PAGE_INVALID;
161	/* For pmd_none() & friends val gets passed as zero. */
162	if (level != 4 && !val)
163		prot = _PAGE_INVALID;
164	/* Final flush from generic code. */
165	if (level == -1)
166		addr = max_addr;
167	if (st->level == -1) {
168		pt_dump_seq_printf(m, "---[ %s ]---\n", st->marker->name);
169		st->start_address = addr;
170		st->current_prot = prot;
171		st->level = level;
172	} else if (prot != st->current_prot || level != st->level ||
173		   addr >= st->marker[1].start_address) {
174		note_prot_wx(st, addr);
175		pt_dump_seq_printf(m, "0x%0*lx-0x%0*lx ",
176				   width, st->start_address,
177				   width, addr);
178		delta = (addr - st->start_address) >> 10;
179		while (!(delta & 0x3ff) && unit[1]) {
180			delta >>= 10;
181			unit++;
182		}
183		pt_dump_seq_printf(m, "%9lu%c ", delta, *unit);
184		print_prot(m, st->current_prot, st->level);
185		while (addr >= st->marker[1].start_address) {
186			st->marker++;
187			pt_dump_seq_printf(m, "---[ %s ]---\n", st->marker->name);
188		}
189		st->start_address = addr;
190		st->current_prot = prot;
191		st->level = level;
192	}
193}
194
195bool ptdump_check_wx(void)
196{
197	struct pg_state st = {
198		.ptdump = {
199			.note_page = note_page,
200			.range = (struct ptdump_range[]) {
201				{.start = 0, .end = max_addr},
202				{.start = 0, .end = 0},
203			}
204		},
205		.seq = NULL,
206		.level = -1,
207		.current_prot = 0,
208		.check_wx = true,
209		.wx_pages = 0,
210		.start_address = 0,
211		.marker = (struct addr_marker[]) {
212			{ .start_address =  0, .name = NULL},
213			{ .start_address = -1, .name = NULL},
214		},
215	};
216
217	if (!MACHINE_HAS_NX)
218		return true;
219	ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
220	if (st.wx_pages) {
221		pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n", st.wx_pages);
222
223		return false;
224	} else {
225		pr_info("Checked W+X mappings: passed, no %sW+X pages found\n",
226			(nospec_uses_trampoline() || !static_key_enabled(&cpu_has_bear)) ?
227			"unexpected " : "");
228
229		return true;
230	}
231}
232
233#ifdef CONFIG_PTDUMP_DEBUGFS
234static int ptdump_show(struct seq_file *m, void *v)
235{
236	struct pg_state st = {
237		.ptdump = {
238			.note_page = note_page,
239			.range = (struct ptdump_range[]) {
240				{.start = 0, .end = max_addr},
241				{.start = 0, .end = 0},
242			}
243		},
244		.seq = m,
245		.level = -1,
246		.current_prot = 0,
247		.check_wx = false,
248		.wx_pages = 0,
249		.start_address = 0,
250		.marker = address_markers,
251	};
252
253	get_online_mems();
254	mutex_lock(&cpa_mutex);
255	ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
256	mutex_unlock(&cpa_mutex);
257	put_online_mems();
258	return 0;
259}
260DEFINE_SHOW_ATTRIBUTE(ptdump);
261#endif /* CONFIG_PTDUMP_DEBUGFS */
262
263/*
264 * Heapsort from lib/sort.c is not a stable sorting algorithm, do a simple
265 * insertion sort to preserve the original order of markers with the same
266 * start address.
267 */
268static void sort_address_markers(void)
269{
270	struct addr_marker tmp;
271	int i, j;
272
273	for (i = 1; i < ARRAY_SIZE(address_markers) - 1; i++) {
274		tmp = address_markers[i];
275		for (j = i - 1; j >= 0 && address_markers[j].start_address > tmp.start_address; j--)
276			address_markers[j + 1] = address_markers[j];
277		address_markers[j + 1] = tmp;
278	}
279}
280
281static int pt_dump_init(void)
282{
283#ifdef CONFIG_KFENCE
284	unsigned long kfence_start = (unsigned long)__kfence_pool;
285#endif
286	/*
287	 * Figure out the maximum virtual address being accessible with the
288	 * kernel ASCE. We need this to keep the page table walker functions
289	 * from accessing non-existent entries.
290	 */
291	max_addr = (S390_lowcore.kernel_asce.val & _REGION_ENTRY_TYPE_MASK) >> 2;
292	max_addr = 1UL << (max_addr * 11 + 31);
293	address_markers[IDENTITY_AFTER_END_NR].start_address = ident_map_size;
294	address_markers[AMODE31_START_NR].start_address = (unsigned long)__samode31;
295	address_markers[AMODE31_END_NR].start_address = (unsigned long)__eamode31;
296	address_markers[MODULES_NR].start_address = MODULES_VADDR;
297	address_markers[MODULES_END_NR].start_address = MODULES_END;
298	address_markers[ABS_LOWCORE_NR].start_address = __abs_lowcore;
299	address_markers[ABS_LOWCORE_END_NR].start_address = __abs_lowcore + ABS_LOWCORE_MAP_SIZE;
300	address_markers[MEMCPY_REAL_NR].start_address = __memcpy_real_area;
301	address_markers[MEMCPY_REAL_END_NR].start_address = __memcpy_real_area + MEMCPY_REAL_SIZE;
302	address_markers[VMEMMAP_NR].start_address = (unsigned long) vmemmap;
303	address_markers[VMEMMAP_END_NR].start_address = (unsigned long)vmemmap + vmemmap_size;
304	address_markers[VMALLOC_NR].start_address = VMALLOC_START;
305	address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
306#ifdef CONFIG_KFENCE
307	address_markers[KFENCE_START_NR].start_address = kfence_start;
308	address_markers[KFENCE_END_NR].start_address = kfence_start + KFENCE_POOL_SIZE;
309#endif
310	sort_address_markers();
311#ifdef CONFIG_PTDUMP_DEBUGFS
312	debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops);
313#endif /* CONFIG_PTDUMP_DEBUGFS */
314	return 0;
315}
316device_initcall(pt_dump_init);
317