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1 | /* | |
2 | * mmu_audit.c: | |
3 | * | |
4 | * Audit code for KVM MMU | |
5 | * | |
6 | * Copyright (C) 2006 Qumranet, Inc. | |
7 | * Copyright 2010 Red Hat, Inc. and/or its affiliates. | |
8 | * | |
9 | * Authors: | |
10 | * Yaniv Kamay <yaniv@qumranet.com> | |
11 | * Avi Kivity <avi@qumranet.com> | |
12 | * Marcelo Tosatti <mtosatti@redhat.com> | |
13 | * Xiao Guangrong <xiaoguangrong@cn.fujitsu.com> | |
14 | * | |
15 | * This work is licensed under the terms of the GNU GPL, version 2. See | |
16 | * the COPYING file in the top-level directory. | |
17 | * | |
18 | */ | |
19 | ||
20 | #include <linux/ratelimit.h> | |
21 | ||
22 | char const *audit_point_name[] = { | |
23 | "pre page fault", | |
24 | "post page fault", | |
25 | "pre pte write", | |
26 | "post pte write", | |
27 | "pre sync", | |
28 | "post sync" | |
29 | }; | |
30 | ||
31 | #define audit_printk(kvm, fmt, args...) \ | |
32 | printk(KERN_ERR "audit: (%s) error: " \ | |
33 | fmt, audit_point_name[kvm->arch.audit_point], ##args) | |
34 | ||
35 | typedef void (*inspect_spte_fn) (struct kvm_vcpu *vcpu, u64 *sptep, int level); | |
36 | ||
37 | static void __mmu_spte_walk(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, | |
38 | inspect_spte_fn fn, int level) | |
39 | { | |
40 | int i; | |
41 | ||
42 | for (i = 0; i < PT64_ENT_PER_PAGE; ++i) { | |
43 | u64 *ent = sp->spt; | |
44 | ||
45 | fn(vcpu, ent + i, level); | |
46 | ||
47 | if (is_shadow_present_pte(ent[i]) && | |
48 | !is_last_spte(ent[i], level)) { | |
49 | struct kvm_mmu_page *child; | |
50 | ||
51 | child = page_header(ent[i] & PT64_BASE_ADDR_MASK); | |
52 | __mmu_spte_walk(vcpu, child, fn, level - 1); | |
53 | } | |
54 | } | |
55 | } | |
56 | ||
57 | static void mmu_spte_walk(struct kvm_vcpu *vcpu, inspect_spte_fn fn) | |
58 | { | |
59 | int i; | |
60 | struct kvm_mmu_page *sp; | |
61 | ||
62 | if (!VALID_PAGE(vcpu->arch.mmu.root_hpa)) | |
63 | return; | |
64 | ||
65 | if (vcpu->arch.mmu.root_level == PT64_ROOT_LEVEL) { | |
66 | hpa_t root = vcpu->arch.mmu.root_hpa; | |
67 | ||
68 | sp = page_header(root); | |
69 | __mmu_spte_walk(vcpu, sp, fn, PT64_ROOT_LEVEL); | |
70 | return; | |
71 | } | |
72 | ||
73 | for (i = 0; i < 4; ++i) { | |
74 | hpa_t root = vcpu->arch.mmu.pae_root[i]; | |
75 | ||
76 | if (root && VALID_PAGE(root)) { | |
77 | root &= PT64_BASE_ADDR_MASK; | |
78 | sp = page_header(root); | |
79 | __mmu_spte_walk(vcpu, sp, fn, 2); | |
80 | } | |
81 | } | |
82 | ||
83 | return; | |
84 | } | |
85 | ||
86 | typedef void (*sp_handler) (struct kvm *kvm, struct kvm_mmu_page *sp); | |
87 | ||
88 | static void walk_all_active_sps(struct kvm *kvm, sp_handler fn) | |
89 | { | |
90 | struct kvm_mmu_page *sp; | |
91 | ||
92 | list_for_each_entry(sp, &kvm->arch.active_mmu_pages, link) | |
93 | fn(kvm, sp); | |
94 | } | |
95 | ||
96 | static void audit_mappings(struct kvm_vcpu *vcpu, u64 *sptep, int level) | |
97 | { | |
98 | struct kvm_mmu_page *sp; | |
99 | gfn_t gfn; | |
100 | pfn_t pfn; | |
101 | hpa_t hpa; | |
102 | ||
103 | sp = page_header(__pa(sptep)); | |
104 | ||
105 | if (sp->unsync) { | |
106 | if (level != PT_PAGE_TABLE_LEVEL) { | |
107 | audit_printk(vcpu->kvm, "unsync sp: %p " | |
108 | "level = %d\n", sp, level); | |
109 | return; | |
110 | } | |
111 | } | |
112 | ||
113 | if (!is_shadow_present_pte(*sptep) || !is_last_spte(*sptep, level)) | |
114 | return; | |
115 | ||
116 | gfn = kvm_mmu_page_get_gfn(sp, sptep - sp->spt); | |
117 | pfn = gfn_to_pfn_atomic(vcpu->kvm, gfn); | |
118 | ||
119 | if (is_error_pfn(pfn)) | |
120 | return; | |
121 | ||
122 | hpa = pfn << PAGE_SHIFT; | |
123 | if ((*sptep & PT64_BASE_ADDR_MASK) != hpa) | |
124 | audit_printk(vcpu->kvm, "levels %d pfn %llx hpa %llx " | |
125 | "ent %llxn", vcpu->arch.mmu.root_level, pfn, | |
126 | hpa, *sptep); | |
127 | } | |
128 | ||
129 | static void inspect_spte_has_rmap(struct kvm *kvm, u64 *sptep) | |
130 | { | |
131 | static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10); | |
132 | unsigned long *rmapp; | |
133 | struct kvm_mmu_page *rev_sp; | |
134 | gfn_t gfn; | |
135 | ||
136 | rev_sp = page_header(__pa(sptep)); | |
137 | gfn = kvm_mmu_page_get_gfn(rev_sp, sptep - rev_sp->spt); | |
138 | ||
139 | if (!gfn_to_memslot(kvm, gfn)) { | |
140 | if (!__ratelimit(&ratelimit_state)) | |
141 | return; | |
142 | audit_printk(kvm, "no memslot for gfn %llx\n", gfn); | |
143 | audit_printk(kvm, "index %ld of sp (gfn=%llx)\n", | |
144 | (long int)(sptep - rev_sp->spt), rev_sp->gfn); | |
145 | dump_stack(); | |
146 | return; | |
147 | } | |
148 | ||
149 | rmapp = gfn_to_rmap(kvm, gfn, rev_sp->role.level); | |
150 | if (!*rmapp) { | |
151 | if (!__ratelimit(&ratelimit_state)) | |
152 | return; | |
153 | audit_printk(kvm, "no rmap for writable spte %llx\n", | |
154 | *sptep); | |
155 | dump_stack(); | |
156 | } | |
157 | } | |
158 | ||
159 | static void audit_sptes_have_rmaps(struct kvm_vcpu *vcpu, u64 *sptep, int level) | |
160 | { | |
161 | if (is_shadow_present_pte(*sptep) && is_last_spte(*sptep, level)) | |
162 | inspect_spte_has_rmap(vcpu->kvm, sptep); | |
163 | } | |
164 | ||
165 | static void audit_spte_after_sync(struct kvm_vcpu *vcpu, u64 *sptep, int level) | |
166 | { | |
167 | struct kvm_mmu_page *sp = page_header(__pa(sptep)); | |
168 | ||
169 | if (vcpu->kvm->arch.audit_point == AUDIT_POST_SYNC && sp->unsync) | |
170 | audit_printk(vcpu->kvm, "meet unsync sp(%p) after sync " | |
171 | "root.\n", sp); | |
172 | } | |
173 | ||
174 | static void check_mappings_rmap(struct kvm *kvm, struct kvm_mmu_page *sp) | |
175 | { | |
176 | int i; | |
177 | ||
178 | if (sp->role.level != PT_PAGE_TABLE_LEVEL) | |
179 | return; | |
180 | ||
181 | for (i = 0; i < PT64_ENT_PER_PAGE; ++i) { | |
182 | if (!is_rmap_spte(sp->spt[i])) | |
183 | continue; | |
184 | ||
185 | inspect_spte_has_rmap(kvm, sp->spt + i); | |
186 | } | |
187 | } | |
188 | ||
189 | static void audit_write_protection(struct kvm *kvm, struct kvm_mmu_page *sp) | |
190 | { | |
191 | unsigned long *rmapp; | |
192 | u64 *sptep; | |
193 | struct rmap_iterator iter; | |
194 | ||
195 | if (sp->role.direct || sp->unsync || sp->role.invalid) | |
196 | return; | |
197 | ||
198 | rmapp = gfn_to_rmap(kvm, sp->gfn, PT_PAGE_TABLE_LEVEL); | |
199 | ||
200 | for (sptep = rmap_get_first(*rmapp, &iter); sptep; | |
201 | sptep = rmap_get_next(&iter)) { | |
202 | if (is_writable_pte(*sptep)) | |
203 | audit_printk(kvm, "shadow page has writable " | |
204 | "mappings: gfn %llx role %x\n", | |
205 | sp->gfn, sp->role.word); | |
206 | } | |
207 | } | |
208 | ||
209 | static void audit_sp(struct kvm *kvm, struct kvm_mmu_page *sp) | |
210 | { | |
211 | check_mappings_rmap(kvm, sp); | |
212 | audit_write_protection(kvm, sp); | |
213 | } | |
214 | ||
215 | static void audit_all_active_sps(struct kvm *kvm) | |
216 | { | |
217 | walk_all_active_sps(kvm, audit_sp); | |
218 | } | |
219 | ||
220 | static void audit_spte(struct kvm_vcpu *vcpu, u64 *sptep, int level) | |
221 | { | |
222 | audit_sptes_have_rmaps(vcpu, sptep, level); | |
223 | audit_mappings(vcpu, sptep, level); | |
224 | audit_spte_after_sync(vcpu, sptep, level); | |
225 | } | |
226 | ||
227 | static void audit_vcpu_spte(struct kvm_vcpu *vcpu) | |
228 | { | |
229 | mmu_spte_walk(vcpu, audit_spte); | |
230 | } | |
231 | ||
232 | static bool mmu_audit; | |
233 | static struct static_key mmu_audit_key; | |
234 | ||
235 | static void __kvm_mmu_audit(struct kvm_vcpu *vcpu, int point) | |
236 | { | |
237 | static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10); | |
238 | ||
239 | if (!__ratelimit(&ratelimit_state)) | |
240 | return; | |
241 | ||
242 | vcpu->kvm->arch.audit_point = point; | |
243 | audit_all_active_sps(vcpu->kvm); | |
244 | audit_vcpu_spte(vcpu); | |
245 | } | |
246 | ||
247 | static inline void kvm_mmu_audit(struct kvm_vcpu *vcpu, int point) | |
248 | { | |
249 | if (static_key_false((&mmu_audit_key))) | |
250 | __kvm_mmu_audit(vcpu, point); | |
251 | } | |
252 | ||
253 | static void mmu_audit_enable(void) | |
254 | { | |
255 | if (mmu_audit) | |
256 | return; | |
257 | ||
258 | static_key_slow_inc(&mmu_audit_key); | |
259 | mmu_audit = true; | |
260 | } | |
261 | ||
262 | static void mmu_audit_disable(void) | |
263 | { | |
264 | if (!mmu_audit) | |
265 | return; | |
266 | ||
267 | static_key_slow_dec(&mmu_audit_key); | |
268 | mmu_audit = false; | |
269 | } | |
270 | ||
271 | static int mmu_audit_set(const char *val, const struct kernel_param *kp) | |
272 | { | |
273 | int ret; | |
274 | unsigned long enable; | |
275 | ||
276 | ret = kstrtoul(val, 10, &enable); | |
277 | if (ret < 0) | |
278 | return -EINVAL; | |
279 | ||
280 | switch (enable) { | |
281 | case 0: | |
282 | mmu_audit_disable(); | |
283 | break; | |
284 | case 1: | |
285 | mmu_audit_enable(); | |
286 | break; | |
287 | default: | |
288 | return -EINVAL; | |
289 | } | |
290 | ||
291 | return 0; | |
292 | } | |
293 | ||
294 | static struct kernel_param_ops audit_param_ops = { | |
295 | .set = mmu_audit_set, | |
296 | .get = param_get_bool, | |
297 | }; | |
298 | ||
299 | arch_param_cb(mmu_audit, &audit_param_ops, &mmu_audit, 0644); |