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 static 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_4LEVEL) {
  66                 hpa_t root = vcpu->arch.mmu.root_hpa;
  67
  68                 sp = page_header(root);
  69                 __mmu_spte_walk(vcpu, sp, fn, vcpu->arch.mmu.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         kvm_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
 129 static void inspect_spte_has_rmap(struct kvm *kvm, u64 *sptep)
 130 {
 131         static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
 132         struct kvm_rmap_head *rmap_head;
 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         rmap_head = __gfn_to_rmap(gfn, rev_sp->role.level, slot);
 154         if (!rmap_head->val) {
 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
 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
 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
 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_shadow_present_pte(sp->spt[i]))
 187                         continue;
 188
 189                 inspect_spte_has_rmap(kvm, sp->spt + i);
 190         }
 191 }
 192
 193 static void audit_write_protection(struct kvm *kvm, struct kvm_mmu_page *sp)
 194 {
 195         struct kvm_rmap_head *rmap_head;
 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         rmap_head = __gfn_to_rmap(sp->gfn, PT_PAGE_TABLE_LEVEL, slot);
 207
 208         for_each_rmap_spte(rmap_head, &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 }
 215
 216 static void audit_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
 217 {
 218         check_mappings_rmap(kvm, sp);
 219         audit_write_protection(kvm, sp);
 220 }
 221
 222 static void audit_all_active_sps(struct kvm *kvm)
 223 {
 224         walk_all_active_sps(kvm, audit_sp);
 225 }
 226
 227 static void audit_spte(struct kvm_vcpu *vcpu, u64 *sptep, int level)
 228 {
 229         audit_sptes_have_rmaps(vcpu, sptep, level);
 230         audit_mappings(vcpu, sptep, level);
 231         audit_spte_after_sync(vcpu, sptep, level);
 232 }
 233
 234 static void audit_vcpu_spte(struct kvm_vcpu *vcpu)
 235 {
 236         mmu_spte_walk(vcpu, audit_spte);
 237 }
 238
 239 static bool mmu_audit;
 240 static struct static_key mmu_audit_key;
 241
 242 static void __kvm_mmu_audit(struct kvm_vcpu *vcpu, int point)
 243 {
 244         static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
 245
 246         if (!__ratelimit(&ratelimit_state))
 247                 return;
 248
 249         vcpu->kvm->arch.audit_point = point;
 250         audit_all_active_sps(vcpu->kvm);
 251         audit_vcpu_spte(vcpu);
 252 }
 253
 254 static inline void kvm_mmu_audit(struct kvm_vcpu *vcpu, int point)
 255 {
 256         if (static_key_false((&mmu_audit_key)))
 257                 __kvm_mmu_audit(vcpu, point);
 258 }
 259
 260 static void mmu_audit_enable(void)
 261 {
 262         if (mmu_audit)
 263                 return;
 264
 265         static_key_slow_inc(&mmu_audit_key);
 266         mmu_audit = true;
 267 }
 268
 269 static void mmu_audit_disable(void)
 270 {
 271         if (!mmu_audit)
 272                 return;
 273
 274         static_key_slow_dec(&mmu_audit_key);
 275         mmu_audit = false;
 276 }
 277
 278 static int mmu_audit_set(const char *val, const struct kernel_param *kp)
 279 {
 280         int ret;
 281         unsigned long enable;
 282
 283         ret = kstrtoul(val, 10, &enable);
 284         if (ret < 0)
 285                 return -EINVAL;
 286
 287         switch (enable) {
 288         case 0:
 289                 mmu_audit_disable();
 290                 break;
 291         case 1:
 292                 mmu_audit_enable();
 293                 break;
 294         default:
 295                 return -EINVAL;
 296         }
 297
 298         return 0;
 299 }
 300
 301 static const struct kernel_param_ops audit_param_ops = {
 302         .set = mmu_audit_set,
 303         .get = param_get_bool,
 304 };
 305
 306 arch_param_cb(mmu_audit, &audit_param_ops, &mmu_audit, 0644);