1 // SPDX-License-Identifier: GPL-2.0
2
3 #include <linux/pagewalk.h>
4 #include <linux/debugfs.h>
5 #include <linux/ptdump.h>
6 #include <linux/kasan.h>
7
8 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
9 /*
10 * This is an optimization for KASAN=y case. Since all kasan page tables
11 * eventually point to the kasan_early_shadow_page we could call note_page()
12 * right away without walking through lower level page tables. This saves
13 * us dozens of seconds (minutes for 5-level config) while checking for
14 * W+X mapping or reading kernel_page_tables debugfs file.
15 */
16 static inline int note_kasan_page_table(struct mm_walk *walk,
17 unsigned long addr)
18 {
19 struct ptdump_state *st = walk->private;
20
21 st->note_page(st, addr, 4, pte_val(kasan_early_shadow_pte[0]));
22
23 walk->action = ACTION_CONTINUE;
24
25 return 0;
26 }
27 #endif
28
29 static int ptdump_pgd_entry(pgd_t *pgd, unsigned long addr,
30 unsigned long next, struct mm_walk *walk)
31 {
32 struct ptdump_state *st = walk->private;
33 pgd_t val = READ_ONCE(*pgd);
34
35 #if CONFIG_PGTABLE_LEVELS > 4 && \
36 (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS))
37 if (pgd_page(val) == virt_to_page(lm_alias(kasan_early_shadow_p4d)))
38 return note_kasan_page_table(walk, addr);
39 #endif
40
41 if (st->effective_prot)
42 st->effective_prot(st, 0, pgd_val(val));
43
44 if (pgd_leaf(val)) {
45 st->note_page(st, addr, 0, pgd_val(val));
46 walk->action = ACTION_CONTINUE;
47 }
48
49 return 0;
50 }
51
52 static int ptdump_p4d_entry(p4d_t *p4d, unsigned long addr,
53 unsigned long next, struct mm_walk *walk)
54 {
55 struct ptdump_state *st = walk->private;
56 p4d_t val = READ_ONCE(*p4d);
57
58 #if CONFIG_PGTABLE_LEVELS > 3 && \
59 (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS))
60 if (p4d_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pud)))
61 return note_kasan_page_table(walk, addr);
62 #endif
63
64 if (st->effective_prot)
65 st->effective_prot(st, 1, p4d_val(val));
66
67 if (p4d_leaf(val)) {
68 st->note_page(st, addr, 1, p4d_val(val));
69 walk->action = ACTION_CONTINUE;
70 }
71
72 return 0;
73 }
74
75 static int ptdump_pud_entry(pud_t *pud, unsigned long addr,
76 unsigned long next, struct mm_walk *walk)
77 {
78 struct ptdump_state *st = walk->private;
79 pud_t val = READ_ONCE(*pud);
80
81 #if CONFIG_PGTABLE_LEVELS > 2 && \
82 (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS))
83 if (pud_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pmd)))
84 return note_kasan_page_table(walk, addr);
85 #endif
86
87 if (st->effective_prot)
88 st->effective_prot(st, 2, pud_val(val));
89
90 if (pud_leaf(val)) {
91 st->note_page(st, addr, 2, pud_val(val));
92 walk->action = ACTION_CONTINUE;
93 }
94
95 return 0;
96 }
97
98 static int ptdump_pmd_entry(pmd_t *pmd, unsigned long addr,
99 unsigned long next, struct mm_walk *walk)
100 {
101 struct ptdump_state *st = walk->private;
102 pmd_t val = READ_ONCE(*pmd);
103
104 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
105 if (pmd_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pte)))
106 return note_kasan_page_table(walk, addr);
107 #endif
108
109 if (st->effective_prot)
110 st->effective_prot(st, 3, pmd_val(val));
111 if (pmd_leaf(val)) {
112 st->note_page(st, addr, 3, pmd_val(val));
113 walk->action = ACTION_CONTINUE;
114 }
115
116 return 0;
117 }
118
119 static int ptdump_pte_entry(pte_t *pte, unsigned long addr,
120 unsigned long next, struct mm_walk *walk)
121 {
122 struct ptdump_state *st = walk->private;
123 pte_t val = ptep_get_lockless(pte);
124
125 if (st->effective_prot)
126 st->effective_prot(st, 4, pte_val(val));
127
128 st->note_page(st, addr, 4, pte_val(val));
129
130 return 0;
131 }
132
133 static int ptdump_hole(unsigned long addr, unsigned long next,
134 int depth, struct mm_walk *walk)
135 {
136 struct ptdump_state *st = walk->private;
137
138 st->note_page(st, addr, depth, 0);
139
140 return 0;
141 }
142
143 static const struct mm_walk_ops ptdump_ops = {
144 .pgd_entry = ptdump_pgd_entry,
145 .p4d_entry = ptdump_p4d_entry,
146 .pud_entry = ptdump_pud_entry,
147 .pmd_entry = ptdump_pmd_entry,
148 .pte_entry = ptdump_pte_entry,
149 .pte_hole = ptdump_hole,
150 };
151
152 void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd)
153 {
154 const struct ptdump_range *range = st->range;
155
156 mmap_write_lock(mm);
157 while (range->start != range->end) {
158 walk_page_range_novma(mm, range->start, range->end,
159 &ptdump_ops, pgd, st);
160 range++;
161 }
162 mmap_write_unlock(mm);
163
164 /* Flush out the last page */
165 st->note_page(st, 0, -1, 0);
166 }
167
168 static int check_wx_show(struct seq_file *m, void *v)
169 {
170 if (ptdump_check_wx())
171 seq_puts(m, "SUCCESS\n");
172 else
173 seq_puts(m, "FAILED\n");
174
175 return 0;
176 }
177
178 DEFINE_SHOW_ATTRIBUTE(check_wx);
179
180 static int ptdump_debugfs_init(void)
181 {
182 debugfs_create_file("check_wx_pages", 0400, NULL, NULL, &check_wx_fops);
183
184 return 0;
185 }
186
187 device_initcall(ptdump_debugfs_init);
188
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