1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * mmu_audit.c:
4 *
5 * Audit code for KVM MMU
6 *
7 * Copyright (C) 2006 Qumranet, Inc.
8 * Copyright 2010 Red Hat, Inc. and/or its affiliates.
9 *
10 * Authors:
11 * Yaniv Kamay <yaniv@qumranet.com>
12 * Avi Kivity <avi@qumranet.com>
13 * Marcelo Tosatti <mtosatti@redhat.com>
14 * Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
15 */
16
17 #include <linux/ratelimit.h>
18
19 static char const *audit_point_name[] = {
20 "pre page fault",
21 "post page fault",
22 "pre pte write",
23 "post pte write",
24 "pre sync",
25 "post sync"
26 };
27
28 #define audit_printk(kvm, fmt, args...) \
29 printk(KERN_ERR "audit: (%s) error: " \
30 fmt, audit_point_name[kvm->arch.audit_point], ##args)
31
32 typedef void (*inspect_spte_fn) (struct kvm_vcpu *vcpu, u64 *sptep, int level);
33
__mmu_spte_walk(struct kvm_vcpu * vcpu,struct kvm_mmu_page * sp,inspect_spte_fn fn,int level)34 static void __mmu_spte_walk(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
35 inspect_spte_fn fn, int level)
36 {
37 int i;
38
39 for (i = 0; i < PT64_ENT_PER_PAGE; ++i) {
40 u64 *ent = sp->spt;
41
42 fn(vcpu, ent + i, level);
43
44 if (is_shadow_present_pte(ent[i]) &&
45 !is_last_spte(ent[i], level)) {
46 struct kvm_mmu_page *child;
47
48 child = to_shadow_page(ent[i] & PT64_BASE_ADDR_MASK);
49 __mmu_spte_walk(vcpu, child, fn, level - 1);
50 }
51 }
52 }
53
mmu_spte_walk(struct kvm_vcpu * vcpu,inspect_spte_fn fn)54 static void mmu_spte_walk(struct kvm_vcpu *vcpu, inspect_spte_fn fn)
55 {
56 int i;
57 struct kvm_mmu_page *sp;
58
59 if (!VALID_PAGE(vcpu->arch.mmu->root_hpa))
60 return;
61
62 if (vcpu->arch.mmu->root_level >= PT64_ROOT_4LEVEL) {
63 hpa_t root = vcpu->arch.mmu->root_hpa;
64
65 sp = to_shadow_page(root);
66 __mmu_spte_walk(vcpu, sp, fn, vcpu->arch.mmu->root_level);
67 return;
68 }
69
70 for (i = 0; i < 4; ++i) {
71 hpa_t root = vcpu->arch.mmu->pae_root[i];
72
73 if (root && VALID_PAGE(root)) {
74 root &= PT64_BASE_ADDR_MASK;
75 sp = to_shadow_page(root);
76 __mmu_spte_walk(vcpu, sp, fn, 2);
77 }
78 }
79
80 return;
81 }
82
83 typedef void (*sp_handler) (struct kvm *kvm, struct kvm_mmu_page *sp);
84
walk_all_active_sps(struct kvm * kvm,sp_handler fn)85 static void walk_all_active_sps(struct kvm *kvm, sp_handler fn)
86 {
87 struct kvm_mmu_page *sp;
88
89 list_for_each_entry(sp, &kvm->arch.active_mmu_pages, link)
90 fn(kvm, sp);
91 }
92
audit_mappings(struct kvm_vcpu * vcpu,u64 * sptep,int level)93 static void audit_mappings(struct kvm_vcpu *vcpu, u64 *sptep, int level)
94 {
95 struct kvm_mmu_page *sp;
96 gfn_t gfn;
97 kvm_pfn_t pfn;
98 hpa_t hpa;
99
100 sp = sptep_to_sp(sptep);
101
102 if (sp->unsync) {
103 if (level != PG_LEVEL_4K) {
104 audit_printk(vcpu->kvm, "unsync sp: %p "
105 "level = %d\n", sp, level);
106 return;
107 }
108 }
109
110 if (!is_shadow_present_pte(*sptep) || !is_last_spte(*sptep, level))
111 return;
112
113 gfn = kvm_mmu_page_get_gfn(sp, sptep - sp->spt);
114 pfn = kvm_vcpu_gfn_to_pfn_atomic(vcpu, gfn);
115
116 if (is_error_pfn(pfn))
117 return;
118
119 hpa = pfn << PAGE_SHIFT;
120 if ((*sptep & PT64_BASE_ADDR_MASK) != hpa)
121 audit_printk(vcpu->kvm, "levels %d pfn %llx hpa %llx "
122 "ent %llxn", vcpu->arch.mmu->root_level, pfn,
123 hpa, *sptep);
124 }
125
inspect_spte_has_rmap(struct kvm * kvm,u64 * sptep)126 static void inspect_spte_has_rmap(struct kvm *kvm, u64 *sptep)
127 {
128 static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
129 struct kvm_rmap_head *rmap_head;
130 struct kvm_mmu_page *rev_sp;
131 struct kvm_memslots *slots;
132 struct kvm_memory_slot *slot;
133 gfn_t gfn;
134
135 rev_sp = sptep_to_sp(sptep);
136 gfn = kvm_mmu_page_get_gfn(rev_sp, sptep - rev_sp->spt);
137
138 slots = kvm_memslots_for_spte_role(kvm, rev_sp->role);
139 slot = __gfn_to_memslot(slots, gfn);
140 if (!slot) {
141 if (!__ratelimit(&ratelimit_state))
142 return;
143 audit_printk(kvm, "no memslot for gfn %llx\n", gfn);
144 audit_printk(kvm, "index %ld of sp (gfn=%llx)\n",
145 (long int)(sptep - rev_sp->spt), rev_sp->gfn);
146 dump_stack();
147 return;
148 }
149
150 rmap_head = __gfn_to_rmap(gfn, rev_sp->role.level, slot);
151 if (!rmap_head->val) {
152 if (!__ratelimit(&ratelimit_state))
153 return;
154 audit_printk(kvm, "no rmap for writable spte %llx\n",
155 *sptep);
156 dump_stack();
157 }
158 }
159
audit_sptes_have_rmaps(struct kvm_vcpu * vcpu,u64 * sptep,int level)160 static void audit_sptes_have_rmaps(struct kvm_vcpu *vcpu, u64 *sptep, int level)
161 {
162 if (is_shadow_present_pte(*sptep) && is_last_spte(*sptep, level))
163 inspect_spte_has_rmap(vcpu->kvm, sptep);
164 }
165
audit_spte_after_sync(struct kvm_vcpu * vcpu,u64 * sptep,int level)166 static void audit_spte_after_sync(struct kvm_vcpu *vcpu, u64 *sptep, int level)
167 {
168 struct kvm_mmu_page *sp = sptep_to_sp(sptep);
169
170 if (vcpu->kvm->arch.audit_point == AUDIT_POST_SYNC && sp->unsync)
171 audit_printk(vcpu->kvm, "meet unsync sp(%p) after sync "
172 "root.\n", sp);
173 }
174
check_mappings_rmap(struct kvm * kvm,struct kvm_mmu_page * sp)175 static void check_mappings_rmap(struct kvm *kvm, struct kvm_mmu_page *sp)
176 {
177 int i;
178
179 if (sp->role.level != PG_LEVEL_4K)
180 return;
181
182 for (i = 0; i < PT64_ENT_PER_PAGE; ++i) {
183 if (!is_shadow_present_pte(sp->spt[i]))
184 continue;
185
186 inspect_spte_has_rmap(kvm, sp->spt + i);
187 }
188 }
189
audit_write_protection(struct kvm * kvm,struct kvm_mmu_page * sp)190 static void audit_write_protection(struct kvm *kvm, struct kvm_mmu_page *sp)
191 {
192 struct kvm_rmap_head *rmap_head;
193 u64 *sptep;
194 struct rmap_iterator iter;
195 struct kvm_memslots *slots;
196 struct kvm_memory_slot *slot;
197
198 if (sp->role.direct || sp->unsync || sp->role.invalid)
199 return;
200
201 slots = kvm_memslots_for_spte_role(kvm, sp->role);
202 slot = __gfn_to_memslot(slots, sp->gfn);
203 rmap_head = __gfn_to_rmap(sp->gfn, PG_LEVEL_4K, slot);
204
205 for_each_rmap_spte(rmap_head, &iter, sptep) {
206 if (is_writable_pte(*sptep))
207 audit_printk(kvm, "shadow page has writable "
208 "mappings: gfn %llx role %x\n",
209 sp->gfn, sp->role.word);
210 }
211 }
212
audit_sp(struct kvm * kvm,struct kvm_mmu_page * sp)213 static void audit_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
214 {
215 check_mappings_rmap(kvm, sp);
216 audit_write_protection(kvm, sp);
217 }
218
audit_all_active_sps(struct kvm * kvm)219 static void audit_all_active_sps(struct kvm *kvm)
220 {
221 walk_all_active_sps(kvm, audit_sp);
222 }
223
audit_spte(struct kvm_vcpu * vcpu,u64 * sptep,int level)224 static void audit_spte(struct kvm_vcpu *vcpu, u64 *sptep, int level)
225 {
226 audit_sptes_have_rmaps(vcpu, sptep, level);
227 audit_mappings(vcpu, sptep, level);
228 audit_spte_after_sync(vcpu, sptep, level);
229 }
230
audit_vcpu_spte(struct kvm_vcpu * vcpu)231 static void audit_vcpu_spte(struct kvm_vcpu *vcpu)
232 {
233 mmu_spte_walk(vcpu, audit_spte);
234 }
235
236 static bool mmu_audit;
237 static struct static_key mmu_audit_key;
238
__kvm_mmu_audit(struct kvm_vcpu * vcpu,int point)239 static void __kvm_mmu_audit(struct kvm_vcpu *vcpu, int point)
240 {
241 static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
242
243 if (!__ratelimit(&ratelimit_state))
244 return;
245
246 vcpu->kvm->arch.audit_point = point;
247 audit_all_active_sps(vcpu->kvm);
248 audit_vcpu_spte(vcpu);
249 }
250
kvm_mmu_audit(struct kvm_vcpu * vcpu,int point)251 static inline void kvm_mmu_audit(struct kvm_vcpu *vcpu, int point)
252 {
253 if (static_key_false((&mmu_audit_key)))
254 __kvm_mmu_audit(vcpu, point);
255 }
256
mmu_audit_enable(void)257 static void mmu_audit_enable(void)
258 {
259 if (mmu_audit)
260 return;
261
262 static_key_slow_inc(&mmu_audit_key);
263 mmu_audit = true;
264 }
265
mmu_audit_disable(void)266 static void mmu_audit_disable(void)
267 {
268 if (!mmu_audit)
269 return;
270
271 static_key_slow_dec(&mmu_audit_key);
272 mmu_audit = false;
273 }
274
mmu_audit_set(const char * val,const struct kernel_param * kp)275 static int mmu_audit_set(const char *val, const struct kernel_param *kp)
276 {
277 int ret;
278 unsigned long enable;
279
280 ret = kstrtoul(val, 10, &enable);
281 if (ret < 0)
282 return -EINVAL;
283
284 switch (enable) {
285 case 0:
286 mmu_audit_disable();
287 break;
288 case 1:
289 mmu_audit_enable();
290 break;
291 default:
292 return -EINVAL;
293 }
294
295 return 0;
296 }
297
298 static const struct kernel_param_ops audit_param_ops = {
299 .set = mmu_audit_set,
300 .get = param_get_bool,
301 };
302
303 arch_param_cb(mmu_audit, &audit_param_ops, &mmu_audit, 0644);
304