arch/x86/kvm/mmu_audit.c

   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 = strict_strtoul(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);