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                 kvm_release_pfn_clean(pfn);
 121                 return;
 122         }
 123
 124         hpa =  pfn << PAGE_SHIFT;
 125         if ((*sptep & PT64_BASE_ADDR_MASK) != hpa)
 126                 audit_printk(vcpu->kvm, "levels %d pfn %llx hpa %llx "
 127                              "ent %llxn", vcpu->arch.mmu.root_level, pfn,
 128                              hpa, *sptep);
 129 }
 130
 131 static void inspect_spte_has_rmap(struct kvm *kvm, u64 *sptep)
 132 {
 133         static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
 134         unsigned long *rmapp;
 135         struct kvm_mmu_page *rev_sp;
 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         if (!gfn_to_memslot(kvm, gfn)) {
 142                 if (!__ratelimit(&ratelimit_state))
 143                         return;
 144                 audit_printk(kvm, "no memslot for gfn %llx\n", gfn);
 145                 audit_printk(kvm, "index %ld of sp (gfn=%llx)\n",
 146                        (long int)(sptep - rev_sp->spt), rev_sp->gfn);
 147                 dump_stack();
 148                 return;
 149         }
 150
 151         rmapp = gfn_to_rmap(kvm, gfn, rev_sp->role.level);
 152         if (!*rmapp) {
 153                 if (!__ratelimit(&ratelimit_state))
 154                         return;
 155                 audit_printk(kvm, "no rmap for writable spte %llx\n",
 156                              *sptep);
 157                 dump_stack();
 158         }
 159 }
 160
 161 static void audit_sptes_have_rmaps(struct kvm_vcpu *vcpu, u64 *sptep, int level)
 162 {
 163         if (is_shadow_present_pte(*sptep) && is_last_spte(*sptep, level))
 164                 inspect_spte_has_rmap(vcpu->kvm, sptep);
 165 }
 166
 167 static void audit_spte_after_sync(struct kvm_vcpu *vcpu, u64 *sptep, int level)
 168 {
 169         struct kvm_mmu_page *sp = page_header(__pa(sptep));
 170
 171         if (vcpu->kvm->arch.audit_point == AUDIT_POST_SYNC && sp->unsync)
 172                 audit_printk(vcpu->kvm, "meet unsync sp(%p) after sync "
 173                              "root.\n", sp);
 174 }
 175
 176 static void check_mappings_rmap(struct kvm *kvm, struct kvm_mmu_page *sp)
 177 {
 178         int i;
 179
 180         if (sp->role.level != PT_PAGE_TABLE_LEVEL)
 181                 return;
 182
 183         for (i = 0; i < PT64_ENT_PER_PAGE; ++i) {
 184                 if (!is_rmap_spte(sp->spt[i]))
 185                         continue;
 186
 187                 inspect_spte_has_rmap(kvm, sp->spt + i);
 188         }
 189 }
 190
 191 static void audit_write_protection(struct kvm *kvm, struct kvm_mmu_page *sp)
 192 {
 193         struct kvm_memory_slot *slot;
 194         unsigned long *rmapp;
 195         u64 *spte;
 196
 197         if (sp->role.direct || sp->unsync || sp->role.invalid)
 198                 return;
 199
 200         slot = gfn_to_memslot(kvm, sp->gfn);
 201         rmapp = &slot->rmap[sp->gfn - slot->base_gfn];
 202
 203         spte = rmap_next(rmapp, NULL);
 204         while (spte) {
 205                 if (is_writable_pte(*spte))
 206                         audit_printk(kvm, "shadow page has writable "
 207                                      "mappings: gfn %llx role %x\n",
 208                                      sp->gfn, sp->role.word);
 209                 spte = rmap_next(rmapp, spte);
 210         }
 211 }
 212
 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
 219 static void audit_all_active_sps(struct kvm *kvm)
 220 {
 221         walk_all_active_sps(kvm, audit_sp);
 222 }
 223
 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
 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
 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
 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
 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
 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
 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 = strict_strtoul(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 struct kernel_param_ops audit_param_ops = {
 299         .set = mmu_audit_set,
 300         .get = param_get_bool,
 301 };
 302
 303 module_param_cb(mmu_audit, &audit_param_ops, &mmu_audit, 0644);