arch/x86/kvm/mmu_audit.c

   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
  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 = page_header(ent[i] & PT64_BASE_ADDR_MASK);
  49                         __mmu_spte_walk(vcpu, child, fn, level - 1);
  50                 }
  51         }
  52 }
  53
  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 = page_header(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 = page_header(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
  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
  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 = page_header(__pa(sptep));
 101
 102         if (sp->unsync) {
 103                 if (level != PT_PAGE_TABLE_LEVEL) {
 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
 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 = page_header(__pa(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
 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
 166 static void audit_spte_after_sync(struct kvm_vcpu *vcpu, u64 *sptep, int level)
 167 {
 168         struct kvm_mmu_page *sp = page_header(__pa(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
 175 static void check_mappings_rmap(struct kvm *kvm, struct kvm_mmu_page *sp)
 176 {
 177         int i;
 178
 179         if (sp->role.level != PT_PAGE_TABLE_LEVEL)
 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
 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, PT_PAGE_TABLE_LEVEL, 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
 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 = 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);