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
__mmu_spte_walk(struct kvm_vcpu * vcpu,struct kvm_mmu_page * sp,inspect_spte_fn fn,int level)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
mmu_spte_walk(struct kvm_vcpu * vcpu,inspect_spte_fn fn)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
walk_all_active_sps(struct kvm * kvm,sp_handler fn)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
audit_mappings(struct kvm_vcpu * vcpu,u64 * sptep,int level)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 = kvm_vcpu_gfn_to_pfn_atomic(vcpu, 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
inspect_spte_has_rmap(struct kvm * kvm,u64 * sptep)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 struct kvm_memslots *slots;
135 struct kvm_memory_slot *slot;
136 gfn_t gfn;
137
138 rev_sp = page_header(__pa(sptep));
139 gfn = kvm_mmu_page_get_gfn(rev_sp, sptep - rev_sp->spt);
140
141 slots = kvm_memslots_for_spte_role(kvm, rev_sp->role);
142 slot = __gfn_to_memslot(slots, gfn);
143 if (!slot) {
144 if (!__ratelimit(&ratelimit_state))
145 return;
146 audit_printk(kvm, "no memslot for gfn %llx\n", gfn);
147 audit_printk(kvm, "index %ld of sp (gfn=%llx)\n",
148 (long int)(sptep - rev_sp->spt), rev_sp->gfn);
149 dump_stack();
150 return;
151 }
152
153 rmapp = __gfn_to_rmap(gfn, rev_sp->role.level, slot);
154 if (!*rmapp) {
155 if (!__ratelimit(&ratelimit_state))
156 return;
157 audit_printk(kvm, "no rmap for writable spte %llx\n",
158 *sptep);
159 dump_stack();
160 }
161 }
162
audit_sptes_have_rmaps(struct kvm_vcpu * vcpu,u64 * sptep,int level)163 static void audit_sptes_have_rmaps(struct kvm_vcpu *vcpu, u64 *sptep, int level)
164 {
165 if (is_shadow_present_pte(*sptep) && is_last_spte(*sptep, level))
166 inspect_spte_has_rmap(vcpu->kvm, sptep);
167 }
168
audit_spte_after_sync(struct kvm_vcpu * vcpu,u64 * sptep,int level)169 static void audit_spte_after_sync(struct kvm_vcpu *vcpu, u64 *sptep, int level)
170 {
171 struct kvm_mmu_page *sp = page_header(__pa(sptep));
172
173 if (vcpu->kvm->arch.audit_point == AUDIT_POST_SYNC && sp->unsync)
174 audit_printk(vcpu->kvm, "meet unsync sp(%p) after sync "
175 "root.\n", sp);
176 }
177
check_mappings_rmap(struct kvm * kvm,struct kvm_mmu_page * sp)178 static void check_mappings_rmap(struct kvm *kvm, struct kvm_mmu_page *sp)
179 {
180 int i;
181
182 if (sp->role.level != PT_PAGE_TABLE_LEVEL)
183 return;
184
185 for (i = 0; i < PT64_ENT_PER_PAGE; ++i) {
186 if (!is_rmap_spte(sp->spt[i]))
187 continue;
188
189 inspect_spte_has_rmap(kvm, sp->spt + i);
190 }
191 }
192
audit_write_protection(struct kvm * kvm,struct kvm_mmu_page * sp)193 static void audit_write_protection(struct kvm *kvm, struct kvm_mmu_page *sp)
194 {
195 unsigned long *rmapp;
196 u64 *sptep;
197 struct rmap_iterator iter;
198 struct kvm_memslots *slots;
199 struct kvm_memory_slot *slot;
200
201 if (sp->role.direct || sp->unsync || sp->role.invalid)
202 return;
203
204 slots = kvm_memslots_for_spte_role(kvm, sp->role);
205 slot = __gfn_to_memslot(slots, sp->gfn);
206 rmapp = __gfn_to_rmap(sp->gfn, PT_PAGE_TABLE_LEVEL, slot);
207
208 for_each_rmap_spte(rmapp, &iter, sptep)
209 if (is_writable_pte(*sptep))
210 audit_printk(kvm, "shadow page has writable "
211 "mappings: gfn %llx role %x\n",
212 sp->gfn, sp->role.word);
213 }
214
audit_sp(struct kvm * kvm,struct kvm_mmu_page * sp)215 static void audit_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
216 {
217 check_mappings_rmap(kvm, sp);
218 audit_write_protection(kvm, sp);
219 }
220
audit_all_active_sps(struct kvm * kvm)221 static void audit_all_active_sps(struct kvm *kvm)
222 {
223 walk_all_active_sps(kvm, audit_sp);
224 }
225
audit_spte(struct kvm_vcpu * vcpu,u64 * sptep,int level)226 static void audit_spte(struct kvm_vcpu *vcpu, u64 *sptep, int level)
227 {
228 audit_sptes_have_rmaps(vcpu, sptep, level);
229 audit_mappings(vcpu, sptep, level);
230 audit_spte_after_sync(vcpu, sptep, level);
231 }
232
audit_vcpu_spte(struct kvm_vcpu * vcpu)233 static void audit_vcpu_spte(struct kvm_vcpu *vcpu)
234 {
235 mmu_spte_walk(vcpu, audit_spte);
236 }
237
238 static bool mmu_audit;
239 static struct static_key mmu_audit_key;
240
__kvm_mmu_audit(struct kvm_vcpu * vcpu,int point)241 static void __kvm_mmu_audit(struct kvm_vcpu *vcpu, int point)
242 {
243 static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
244
245 if (!__ratelimit(&ratelimit_state))
246 return;
247
248 vcpu->kvm->arch.audit_point = point;
249 audit_all_active_sps(vcpu->kvm);
250 audit_vcpu_spte(vcpu);
251 }
252
kvm_mmu_audit(struct kvm_vcpu * vcpu,int point)253 static inline void kvm_mmu_audit(struct kvm_vcpu *vcpu, int point)
254 {
255 if (static_key_false((&mmu_audit_key)))
256 __kvm_mmu_audit(vcpu, point);
257 }
258
mmu_audit_enable(void)259 static void mmu_audit_enable(void)
260 {
261 if (mmu_audit)
262 return;
263
264 static_key_slow_inc(&mmu_audit_key);
265 mmu_audit = true;
266 }
267
mmu_audit_disable(void)268 static void mmu_audit_disable(void)
269 {
270 if (!mmu_audit)
271 return;
272
273 static_key_slow_dec(&mmu_audit_key);
274 mmu_audit = false;
275 }
276
mmu_audit_set(const char * val,const struct kernel_param * kp)277 static int mmu_audit_set(const char *val, const struct kernel_param *kp)
278 {
279 int ret;
280 unsigned long enable;
281
282 ret = kstrtoul(val, 10, &enable);
283 if (ret < 0)
284 return -EINVAL;
285
286 switch (enable) {
287 case 0:
288 mmu_audit_disable();
289 break;
290 case 1:
291 mmu_audit_enable();
292 break;
293 default:
294 return -EINVAL;
295 }
296
297 return 0;
298 }
299
300 static const struct kernel_param_ops audit_param_ops = {
301 .set = mmu_audit_set,
302 .get = param_get_bool,
303 };
304
305 arch_param_cb(mmu_audit, &audit_param_ops, &mmu_audit, 0644);
306