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/sort.h>
7 #include <linux/mm.h>
8 #include <linux/kfence.h>
9 #include <linux/kasan.h>
10 #include <asm/kasan.h>
11 #include <asm/abs_lowcore.h>
12 #include <asm/nospec-branch.h>
13 #include <asm/sections.h>
14 #include <asm/maccess.h>
15 
16 static unsigned long max_addr;
17 
18 struct addr_marker {
19 	int is_start;
20 	unsigned long start_address;
21 	unsigned long size;
22 	const char *name;
23 };
24 
25 static struct addr_marker *markers;
26 static unsigned int markers_cnt;
27 
28 struct pg_state {
29 	struct ptdump_state ptdump;
30 	struct seq_file *seq;
31 	int level;
32 	unsigned int current_prot;
33 	bool check_wx;
34 	unsigned long wx_pages;
35 	unsigned long start_address;
36 	const struct addr_marker *marker;
37 };
38 
39 #define pt_dump_seq_printf(m, fmt, args...)	\
40 ({						\
41 	struct seq_file *__m = (m);		\
42 						\
43 	if (__m)				\
44 		seq_printf(__m, fmt, ##args);	\
45 })
46 
47 #define pt_dump_seq_puts(m, fmt)		\
48 ({						\
49 	struct seq_file *__m = (m);		\
50 						\
51 	if (__m)				\
52 		seq_printf(__m, fmt);		\
53 })
54 
print_prot(struct seq_file * m,unsigned int pr,int level)55 static void print_prot(struct seq_file *m, unsigned int pr, int level)
56 {
57 	static const char * const level_name[] =
58 		{ "ASCE", "PGD", "PUD", "PMD", "PTE" };
59 
60 	pt_dump_seq_printf(m, "%s ", level_name[level]);
61 	if (pr & _PAGE_INVALID) {
62 		pt_dump_seq_printf(m, "I\n");
63 		return;
64 	}
65 	pt_dump_seq_puts(m, (pr & _PAGE_PROTECT) ? "RO " : "RW ");
66 	pt_dump_seq_puts(m, (pr & _PAGE_NOEXEC) ? "NX\n" : "X\n");
67 }
68 
note_prot_wx(struct pg_state * st,unsigned long addr)69 static void note_prot_wx(struct pg_state *st, unsigned long addr)
70 {
71 	if (!st->check_wx)
72 		return;
73 	if (st->current_prot & _PAGE_INVALID)
74 		return;
75 	if (st->current_prot & _PAGE_PROTECT)
76 		return;
77 	if (st->current_prot & _PAGE_NOEXEC)
78 		return;
79 	/*
80 	 * The first lowcore page is W+X if spectre mitigations are using
81 	 * trampolines or the BEAR enhancements facility is not installed,
82 	 * in which case we have two lpswe instructions in lowcore that need
83 	 * to be executable.
84 	 */
85 	if (addr == PAGE_SIZE && (nospec_uses_trampoline() || !static_key_enabled(&cpu_has_bear)))
86 		return;
87 	WARN_ONCE(IS_ENABLED(CONFIG_DEBUG_WX),
88 		  "s390/mm: Found insecure W+X mapping at address %pS\n",
89 		  (void *)st->start_address);
90 	st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
91 }
92 
note_page_update_state(struct pg_state * st,unsigned long addr,unsigned int prot,int level)93 static void note_page_update_state(struct pg_state *st, unsigned long addr, unsigned int prot, int level)
94 {
95 	struct seq_file *m = st->seq;
96 
97 	while (addr >= st->marker[1].start_address) {
98 		st->marker++;
99 		pt_dump_seq_printf(m, "---[ %s %s ]---\n", st->marker->name,
100 				   st->marker->is_start ? "Start" : "End");
101 	}
102 	st->start_address = addr;
103 	st->current_prot = prot;
104 	st->level = level;
105 }
106 
note_page(struct ptdump_state * pt_st,unsigned long addr,int level,u64 val)107 static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level, u64 val)
108 {
109 	int width = sizeof(unsigned long) * 2;
110 	static const char units[] = "KMGTPE";
111 	const char *unit = units;
112 	unsigned long delta;
113 	struct pg_state *st;
114 	struct seq_file *m;
115 	unsigned int prot;
116 
117 	st = container_of(pt_st, struct pg_state, ptdump);
118 	m = st->seq;
119 	prot = val & (_PAGE_PROTECT | _PAGE_NOEXEC);
120 	if (level == 4 && (val & _PAGE_INVALID))
121 		prot = _PAGE_INVALID;
122 	/* For pmd_none() & friends val gets passed as zero. */
123 	if (level != 4 && !val)
124 		prot = _PAGE_INVALID;
125 	/* Final flush from generic code. */
126 	if (level == -1)
127 		addr = max_addr;
128 	if (st->level == -1) {
129 		pt_dump_seq_puts(m, "---[ Kernel Virtual Address Space ]---\n");
130 		note_page_update_state(st, addr, prot, level);
131 	} else if (prot != st->current_prot || level != st->level ||
132 		   addr >= st->marker[1].start_address) {
133 		note_prot_wx(st, addr);
134 		pt_dump_seq_printf(m, "0x%0*lx-0x%0*lx ",
135 				   width, st->start_address,
136 				   width, addr);
137 		delta = (addr - st->start_address) >> 10;
138 		while (!(delta & 0x3ff) && unit[1]) {
139 			delta >>= 10;
140 			unit++;
141 		}
142 		pt_dump_seq_printf(m, "%9lu%c ", delta, *unit);
143 		print_prot(m, st->current_prot, st->level);
144 		note_page_update_state(st, addr, prot, level);
145 	}
146 }
147 
ptdump_check_wx(void)148 bool ptdump_check_wx(void)
149 {
150 	struct pg_state st = {
151 		.ptdump = {
152 			.note_page = note_page,
153 			.range = (struct ptdump_range[]) {
154 				{.start = 0, .end = max_addr},
155 				{.start = 0, .end = 0},
156 			}
157 		},
158 		.seq = NULL,
159 		.level = -1,
160 		.current_prot = 0,
161 		.check_wx = true,
162 		.wx_pages = 0,
163 		.start_address = 0,
164 		.marker = (struct addr_marker[]) {
165 			{ .start_address =  0, .name = NULL},
166 			{ .start_address = -1, .name = NULL},
167 		},
168 	};
169 
170 	if (!MACHINE_HAS_NX)
171 		return true;
172 	ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
173 	if (st.wx_pages) {
174 		pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n", st.wx_pages);
175 
176 		return false;
177 	} else {
178 		pr_info("Checked W+X mappings: passed, no %sW+X pages found\n",
179 			(nospec_uses_trampoline() || !static_key_enabled(&cpu_has_bear)) ?
180 			"unexpected " : "");
181 
182 		return true;
183 	}
184 }
185 
186 #ifdef CONFIG_PTDUMP_DEBUGFS
ptdump_show(struct seq_file * m,void * v)187 static int ptdump_show(struct seq_file *m, void *v)
188 {
189 	struct pg_state st = {
190 		.ptdump = {
191 			.note_page = note_page,
192 			.range = (struct ptdump_range[]) {
193 				{.start = 0, .end = max_addr},
194 				{.start = 0, .end = 0},
195 			}
196 		},
197 		.seq = m,
198 		.level = -1,
199 		.current_prot = 0,
200 		.check_wx = false,
201 		.wx_pages = 0,
202 		.start_address = 0,
203 		.marker = markers,
204 	};
205 
206 	get_online_mems();
207 	mutex_lock(&cpa_mutex);
208 	ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
209 	mutex_unlock(&cpa_mutex);
210 	put_online_mems();
211 	return 0;
212 }
213 DEFINE_SHOW_ATTRIBUTE(ptdump);
214 #endif /* CONFIG_PTDUMP_DEBUGFS */
215 
ptdump_cmp(const void * a,const void * b)216 static int ptdump_cmp(const void *a, const void *b)
217 {
218 	const struct addr_marker *ama = a;
219 	const struct addr_marker *amb = b;
220 
221 	if (ama->start_address > amb->start_address)
222 		return 1;
223 	if (ama->start_address < amb->start_address)
224 		return -1;
225 	/*
226 	 * If the start addresses of two markers are identical sort markers in an
227 	 * order that considers areas contained within other areas correctly.
228 	 */
229 	if (ama->is_start && amb->is_start) {
230 		if (ama->size > amb->size)
231 			return -1;
232 		if (ama->size < amb->size)
233 			return 1;
234 		return 0;
235 	}
236 	if (!ama->is_start && !amb->is_start) {
237 		if (ama->size > amb->size)
238 			return 1;
239 		if (ama->size < amb->size)
240 			return -1;
241 		return 0;
242 	}
243 	if (ama->is_start)
244 		return 1;
245 	if (amb->is_start)
246 		return -1;
247 	return 0;
248 }
249 
add_marker(unsigned long start,unsigned long end,const char * name)250 static int add_marker(unsigned long start, unsigned long end, const char *name)
251 {
252 	size_t oldsize, newsize;
253 
254 	oldsize = markers_cnt * sizeof(*markers);
255 	newsize = oldsize + 2 * sizeof(*markers);
256 	if (!oldsize)
257 		markers = kvmalloc(newsize, GFP_KERNEL);
258 	else
259 		markers = kvrealloc(markers, newsize, GFP_KERNEL);
260 	if (!markers)
261 		goto error;
262 	markers[markers_cnt].is_start = 1;
263 	markers[markers_cnt].start_address = start;
264 	markers[markers_cnt].size = end - start;
265 	markers[markers_cnt].name = name;
266 	markers_cnt++;
267 	markers[markers_cnt].is_start = 0;
268 	markers[markers_cnt].start_address = end;
269 	markers[markers_cnt].size = end - start;
270 	markers[markers_cnt].name = name;
271 	markers_cnt++;
272 	return 0;
273 error:
274 	markers_cnt = 0;
275 	return -ENOMEM;
276 }
277 
pt_dump_init(void)278 static int pt_dump_init(void)
279 {
280 #ifdef CONFIG_KFENCE
281 	unsigned long kfence_start = (unsigned long)__kfence_pool;
282 #endif
283 	unsigned long lowcore = (unsigned long)get_lowcore();
284 	int rc;
285 
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 = (get_lowcore()->kernel_asce.val & _REGION_ENTRY_TYPE_MASK) >> 2;
292 	max_addr = 1UL << (max_addr * 11 + 31);
293 	/* start + end markers - must be added first */
294 	rc = add_marker(0, -1UL, NULL);
295 	rc |= add_marker((unsigned long)_stext, (unsigned long)_end, "Kernel Image");
296 	rc |= add_marker(lowcore, lowcore + sizeof(struct lowcore), "Lowcore");
297 	rc |= add_marker(__identity_base, __identity_base + ident_map_size, "Identity Mapping");
298 	rc |= add_marker((unsigned long)__samode31, (unsigned long)__eamode31, "Amode31 Area");
299 	rc |= add_marker(MODULES_VADDR, MODULES_END, "Modules Area");
300 	rc |= add_marker(__abs_lowcore, __abs_lowcore + ABS_LOWCORE_MAP_SIZE, "Lowcore Area");
301 	rc |= add_marker(__memcpy_real_area, __memcpy_real_area + MEMCPY_REAL_SIZE, "Real Memory Copy Area");
302 	rc |= add_marker((unsigned long)vmemmap, (unsigned long)vmemmap + vmemmap_size, "vmemmap Area");
303 	rc |= add_marker(VMALLOC_START, VMALLOC_END, "vmalloc Area");
304 #ifdef CONFIG_KFENCE
305 	rc |= add_marker(kfence_start, kfence_start + KFENCE_POOL_SIZE, "KFence Pool");
306 #endif
307 #ifdef CONFIG_KMSAN
308 	rc |= add_marker(KMSAN_VMALLOC_SHADOW_START, KMSAN_VMALLOC_SHADOW_END, "Kmsan vmalloc Shadow");
309 	rc |= add_marker(KMSAN_VMALLOC_ORIGIN_START, KMSAN_VMALLOC_ORIGIN_END, "Kmsan vmalloc Origins");
310 	rc |= add_marker(KMSAN_MODULES_SHADOW_START, KMSAN_MODULES_SHADOW_END, "Kmsan Modules Shadow");
311 	rc |= add_marker(KMSAN_MODULES_ORIGIN_START, KMSAN_MODULES_ORIGIN_END, "Kmsan Modules Origins");
312 #endif
313 #ifdef CONFIG_KASAN
314 	rc |= add_marker(KASAN_SHADOW_START, KASAN_SHADOW_END, "Kasan Shadow");
315 #endif
316 	if (rc)
317 		goto error;
318 	sort(&markers[1], markers_cnt - 1, sizeof(*markers), ptdump_cmp, NULL);
319 #ifdef CONFIG_PTDUMP_DEBUGFS
320 	debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops);
321 #endif /* CONFIG_PTDUMP_DEBUGFS */
322 	return 0;
323 error:
324 	kvfree(markers);
325 	return -ENOMEM;
326 }
327 device_initcall(pt_dump_init);
328