From: Mihai Donțu <mdo...@bitdefender.com>
This event is sent when a #PF occurs due to a failed permission check
in the shadow page tables, for a page in which the introspection tool
has shown interest.
Signed-off-by: Mihai Donțu <mdo...@bitdefender.com>
Co-developed-by: Adalbert Lazăr <ala...@bitdefender.com>
Signed-off-by: Adalbert Lazăr <ala...@bitdefender.com>
---
Documentation/virt/kvm/kvmi.rst | 66 ++++++++++
arch/x86/include/asm/kvmi_host.h | 1 +
arch/x86/kvm/kvmi.c | 122 ++++++++++++++++++
include/uapi/linux/kvmi.h | 10 ++
.../testing/selftests/kvm/x86_64/kvmi_test.c | 76 +++++++++++
virt/kvm/introspection/kvmi.c | 116 +++++++++++++++++
virt/kvm/introspection/kvmi_int.h | 7 +
virt/kvm/introspection/kvmi_msg.c | 19 +++
8 files changed, 417 insertions(+)
diff --git a/Documentation/virt/kvm/kvmi.rst b/Documentation/virt/kvm/kvmi.rst
index dc96f935320a..c5afb4c91ca2 100644
--- a/Documentation/virt/kvm/kvmi.rst
+++ b/Documentation/virt/kvm/kvmi.rst
@@ -543,6 +543,7 @@ the following events::
KVMI_VCPU_EVENT_DESCRIPTOR
KVMI_VCPU_EVENT_HYPERCALL
KVMI_VCPU_EVENT_MSR
+ KVMI_VCPU_EVENT_PF
KVMI_VCPU_EVENT_XSETBV
When an event is enabled, the introspection tool is notified and
@@ -1398,3 +1399,68 @@ register (see **KVMI_VCPU_CONTROL_EVENTS**).
``kvmi_vcpu_event`` (with the vCPU state), the MSR number (``msr``),
the old value (``old_value``) and the new value (``new_value``) are sent
to the introspection tool. The *CONTINUE* action will set the ``new_val``.
+
+10. KVMI_VCPU_EVENT_PF
+----------------------
+
+:Architectures: x86
+:Versions: >= 1
+:Actions: CONTINUE, CRASH, RETRY
+:Parameters:
+
+::
+
+ struct kvmi_vcpu_event;
+ struct kvmi_vcpu_event_pf {
+ __u64 gva;
+ __u64 gpa;
+ __u8 access;
+ __u8 padding1;
+ __u16 padding2;
+ __u32 padding3;
+ };
+
+:Returns:
+
+::
+
+ struct kvmi_vcpu_hdr;
+ struct kvmi_vcpu_event_reply;
+
+This event is sent when a hypervisor page fault occurs due to a failed
+permission checks, the introspection has been enabled for this event
+(see *KVMI_VCPU_CONTROL_EVENTS*) and the event was generated for a
+page in which the introspection tool has shown interest (ie. has
+previously touched it by adjusting the spte permissions; see
+*KVMI_VM_SET_PAGE_ACCESS*).
+
+These permissions can be used by the introspection tool to guarantee
+the purpose of code areas inside the guest (code, rodata, stack, heap
+etc.) Each attempt at an operation unfitting for a certain memory
+range (eg. execute code in heap) triggers a page fault and gives the
+introspection tool the chance to audit the code attempting the operation.
+
+``kvmi_vcpu_event`` (with the vCPU state), guest virtual address (``gva``)
+if available or ~0 (UNMAPPED_GVA), guest physical address (``gpa``)
+and the ``access`` flags (e.g. KVMI_PAGE_ACCESS_R) are sent to the
+introspection tool.
+
+In case of a restricted read access, the guest address is the location
+of the memory being read. On write access, the guest address is the
+location of the memory being written. On execute access, the guest
+address is the location of the instruction being executed
+(``gva == kvmi_vcpu_event.arch.regs.rip``).
+
+In the current implementation, most of these events are sent during
+emulation. If the page fault has set more than one access bit
+(e.g. r-x/-rw), the introspection tool may receive more than one
+KVMI_VCPU_EVENT_PF and the order depends on the KVM emulator. Another
+cause of multiple events is when the page fault is triggered on access
+crossing the page boundary.
+
+The *CONTINUE* action will continue the page fault handling (e.g. via
+emulation).
+
+The *RETRY* action is used by the introspection tool to retry the
+execution of the current instruction, usually because it changed the
+instruction pointer or the page restrictions.
diff --git a/arch/x86/include/asm/kvmi_host.h b/arch/x86/include/asm/kvmi_host.h
index 420358c4a9ae..31500d3ff69d 100644
--- a/arch/x86/include/asm/kvmi_host.h
+++ b/arch/x86/include/asm/kvmi_host.h
@@ -53,6 +53,7 @@ struct kvm_vcpu_arch_introspection {
};
struct kvm_arch_introspection {
+ struct kvm_page_track_notifier_node kptn_node;
};
#define SLOTS_SIZE BITS_TO_LONGS(KVM_MEM_SLOTS_NUM)
diff --git a/arch/x86/kvm/kvmi.c b/arch/x86/kvm/kvmi.c
index acd4756e0d78..cd64762643d6 100644
--- a/arch/x86/kvm/kvmi.c
+++ b/arch/x86/kvm/kvmi.c
@@ -17,10 +17,26 @@ void kvmi_arch_init_vcpu_events_mask(unsigned long
*supported)
set_bit(KVMI_VCPU_EVENT_HYPERCALL, supported);
set_bit(KVMI_VCPU_EVENT_DESCRIPTOR, supported);
set_bit(KVMI_VCPU_EVENT_MSR, supported);
+ set_bit(KVMI_VCPU_EVENT_PF, supported);
set_bit(KVMI_VCPU_EVENT_TRAP, supported);
set_bit(KVMI_VCPU_EVENT_XSETBV, supported);
}
+static bool kvmi_track_preread(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva,
+ int bytes,
+ struct kvm_page_track_notifier_node *node);
+static bool kvmi_track_prewrite(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva,
+ const u8 *new, int bytes,
+ struct kvm_page_track_notifier_node *node);
+static bool kvmi_track_preexec(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva,
+ struct kvm_page_track_notifier_node *node);
+static void kvmi_track_create_slot(struct kvm *kvm,
+ struct kvm_memory_slot *slot,
+ unsigned long npages,
+ struct kvm_page_track_notifier_node *node);
+static void kvmi_track_flush_slot(struct kvm *kvm, struct kvm_memory_slot
*slot,
+ struct kvm_page_track_notifier_node *node);
+
static unsigned int kvmi_vcpu_mode(const struct kvm_vcpu *vcpu,
const struct kvm_sregs *sregs)
{
@@ -959,3 +975,109 @@ void kvmi_arch_update_page_tracking(struct kvm *kvm,
}
}
}
+
+void kvmi_arch_hook(struct kvm *kvm)
+{
+ struct kvm_introspection *kvmi = KVMI(kvm);
+
+ kvmi->arch.kptn_node.track_preread = kvmi_track_preread;
+ kvmi->arch.kptn_node.track_prewrite = kvmi_track_prewrite;
+ kvmi->arch.kptn_node.track_preexec = kvmi_track_preexec;
+ kvmi->arch.kptn_node.track_create_slot = kvmi_track_create_slot;
+ kvmi->arch.kptn_node.track_flush_slot = kvmi_track_flush_slot;
+
+ kvm_page_track_register_notifier(kvm, &kvmi->arch.kptn_node);
+}
+
+void kvmi_arch_unhook(struct kvm *kvm)
+{
+ struct kvm_introspection *kvmi = KVMI(kvm);
+
+ kvm_page_track_unregister_notifier(kvm, &kvmi->arch.kptn_node);
+}
+
+static bool kvmi_track_preread(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva,
+ int bytes,
+ struct kvm_page_track_notifier_node *node)
+{
+ struct kvm_introspection *kvmi;
+ bool ret = true;
+
+ kvmi = kvmi_get(vcpu->kvm);
+ if (!kvmi)
+ return true;
+
+ if (is_vcpu_event_enabled(vcpu, KVMI_VCPU_EVENT_PF))
+ ret = kvmi_pf_event(vcpu, gpa, gva, KVMI_PAGE_ACCESS_R);
+
+ kvmi_put(vcpu->kvm);
+
+ return ret;
+}
+
+static bool kvmi_track_prewrite(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva,
+ const u8 *new, int bytes,
+ struct kvm_page_track_notifier_node *node)
+{
+ struct kvm_introspection *kvmi;
+ bool ret = true;
+
+ kvmi = kvmi_get(vcpu->kvm);
+ if (!kvmi)
+ return true;
+
+ if (is_vcpu_event_enabled(vcpu, KVMI_VCPU_EVENT_PF))
+ ret = kvmi_pf_event(vcpu, gpa, gva, KVMI_PAGE_ACCESS_W);
+
+ kvmi_put(vcpu->kvm);
+
+ return ret;
+}
+
+static bool kvmi_track_preexec(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva,
+ struct kvm_page_track_notifier_node *node)
+{
+ struct kvm_introspection *kvmi;
+ bool ret = true;
+
+ kvmi = kvmi_get(vcpu->kvm);
+ if (!kvmi)
+ return true;
+
+ if (is_vcpu_event_enabled(vcpu, KVMI_VCPU_EVENT_PF))
+ ret = kvmi_pf_event(vcpu, gpa, gva, KVMI_PAGE_ACCESS_X);
+
+ kvmi_put(vcpu->kvm);
+
+ return ret;
+}
+
+static void kvmi_track_create_slot(struct kvm *kvm,
+ struct kvm_memory_slot *slot,
+ unsigned long npages,
+ struct kvm_page_track_notifier_node *node)
+{
+ struct kvm_introspection *kvmi;
+
+ kvmi = kvmi_get(kvm);
+ if (!kvmi)
+ return;
+
+ kvmi_add_memslot(kvm, slot, npages);
+
+ kvmi_put(kvm);
+}
+
+static void kvmi_track_flush_slot(struct kvm *kvm, struct kvm_memory_slot
*slot,
+ struct kvm_page_track_notifier_node *node)
+{
+ struct kvm_introspection *kvmi;
+
+ kvmi = kvmi_get(kvm);
+ if (!kvmi)
+ return;
+
+ kvmi_remove_memslot(kvm, slot);
+
+ kvmi_put(kvm);
+}
diff --git a/include/uapi/linux/kvmi.h b/include/uapi/linux/kvmi.h
index 42c8e6342fcf..3b432b37b17c 100644
--- a/include/uapi/linux/kvmi.h
+++ b/include/uapi/linux/kvmi.h
@@ -72,6 +72,7 @@ enum {
KVMI_VCPU_EVENT_XSETBV = KVMI_VCPU_EVENT_ID(5),
KVMI_VCPU_EVENT_DESCRIPTOR = KVMI_VCPU_EVENT_ID(6),
KVMI_VCPU_EVENT_MSR = KVMI_VCPU_EVENT_ID(7),
+ KVMI_VCPU_EVENT_PF = KVMI_VCPU_EVENT_ID(8),
KVMI_NEXT_VCPU_EVENT
};
@@ -210,4 +211,13 @@ struct kvmi_vm_set_page_access {
struct kvmi_page_access_entry entries[0];
};
+struct kvmi_vcpu_event_pf {
+ __u64 gva;
+ __u64 gpa;
+ __u8 access;
+ __u8 padding1;
+ __u16 padding2;
+ __u32 padding3;
+};
+
#endif /* _UAPI__LINUX_KVMI_H */
diff --git a/tools/testing/selftests/kvm/x86_64/kvmi_test.c
b/tools/testing/selftests/kvm/x86_64/kvmi_test.c
index c9d6ee57d506..e36b574c264e 100644
--- a/tools/testing/selftests/kvm/x86_64/kvmi_test.c
+++ b/tools/testing/selftests/kvm/x86_64/kvmi_test.c
@@ -47,6 +47,11 @@ struct vcpu_reply {
struct kvmi_vcpu_event_reply reply;
};
+struct pf_ev {
+ struct vcpu_event vcpu_ev;
+ struct kvmi_vcpu_event_pf pf;
+};
+
struct vcpu_worker_data {
struct kvm_vm *vm;
int vcpu_id;
@@ -54,6 +59,10 @@ struct vcpu_worker_data {
bool restart_on_shutdown;
};
+typedef void (*fct_pf_event)(struct kvm_vm *vm, struct kvmi_msg_hdr *hdr,
+ struct pf_ev *ev,
+ struct vcpu_reply *rpl);
+
enum {
GUEST_TEST_NOOP = 0,
GUEST_TEST_BP,
@@ -61,6 +70,7 @@ enum {
GUEST_TEST_DESCRIPTOR,
GUEST_TEST_HYPERCALL,
GUEST_TEST_MSR,
+ GUEST_TEST_PF,
GUEST_TEST_XSETBV,
};
@@ -114,6 +124,11 @@ static void guest_msr_test(void)
wrmsr(MSR_MISC_FEATURES_ENABLES, msr);
}
+static void guest_pf_test(void)
+{
+ *((uint8_t *)test_gva) = GUEST_TEST_PF;
+}
+
/* from fpu/internal.h */
static u64 xgetbv(u32 index)
{
@@ -174,6 +189,9 @@ static void guest_code(void)
case GUEST_TEST_MSR:
guest_msr_test();
break;
+ case GUEST_TEST_PF:
+ guest_pf_test();
+ break;
case GUEST_TEST_XSETBV:
guest_xsetbv_test();
break;
@@ -1738,6 +1756,63 @@ static void test_cmd_vm_set_page_access(struct kvm_vm
*vm)
set_page_access(gpa, full_access);
}
+static void test_pf(struct kvm_vm *vm, fct_pf_event cbk)
+{
+ __u16 event_id = KVMI_VCPU_EVENT_PF;
+ struct vcpu_worker_data data = {
+ .vm = vm,
+ .vcpu_id = VCPU_ID,
+ .test_id = GUEST_TEST_PF,
+ };
+ struct kvmi_msg_hdr hdr;
+ struct vcpu_reply rpl = {};
+ pthread_t vcpu_thread;
+ struct pf_ev ev;
+
+ set_page_access(test_gpa, KVMI_PAGE_ACCESS_R);
+ enable_vcpu_event(vm, event_id);
+
+ *((uint8_t *)test_hva) = ~GUEST_TEST_PF;
+
+ vcpu_thread = start_vcpu_worker(&data);
+
+ receive_vcpu_event(&hdr, &ev.vcpu_ev, sizeof(ev), event_id);
+
+ pr_debug("PF event, gpa 0x%llx, gva 0x%llx, access 0x%x\n",
+ ev.pf.gpa, ev.pf.gva, ev.pf.access);
+
+ TEST_ASSERT(ev.pf.gpa == test_gpa && ev.pf.gva == test_gva,
+ "Unexpected #PF event, gpa 0x%llx (expended 0x%lx), gva 0x%llx
(expected 0x%lx)\n",
+ ev.pf.gpa, test_gpa, ev.pf.gva, test_gva);
+
+ cbk(vm, &hdr, &ev, &rpl);
+
+ wait_vcpu_worker(vcpu_thread);
+
+ TEST_ASSERT(*((uint8_t *)test_hva) == GUEST_TEST_PF,
+ "Write failed, expected 0x%x, result 0x%x\n",
+ GUEST_TEST_PF, *((uint8_t *)test_hva));
+
+ disable_vcpu_event(vm, event_id);
+ set_page_access(test_gpa, KVMI_PAGE_ACCESS_R |
+ KVMI_PAGE_ACCESS_W |
+ KVMI_PAGE_ACCESS_X);
+}
+
+static void cbk_test_event_pf(struct kvm_vm *vm, struct kvmi_msg_hdr *hdr,
+ struct pf_ev *ev, struct vcpu_reply *rpl)
+{
+ set_page_access(test_gpa, KVMI_PAGE_ACCESS_R | KVMI_PAGE_ACCESS_W);
+
+ reply_to_event(hdr, &ev->vcpu_ev, KVMI_EVENT_ACTION_RETRY,
+ rpl, sizeof(*rpl));
+}
+
+static void test_event_pf(struct kvm_vm *vm)
+{
+ test_pf(vm, cbk_test_event_pf);
+}
+
static void test_introspection(struct kvm_vm *vm)
{
srandom(time(0));
@@ -1771,6 +1846,7 @@ static void test_introspection(struct kvm_vm *vm)
test_event_descriptor(vm);
test_cmd_vcpu_control_msr(vm);
test_cmd_vm_set_page_access(vm);
+ test_event_pf(vm);
unhook_introspection(vm);
}
diff --git a/virt/kvm/introspection/kvmi.c b/virt/kvm/introspection/kvmi.c
index c21c705ccddf..841779143609 100644
--- a/virt/kvm/introspection/kvmi.c
+++ b/virt/kvm/introspection/kvmi.c
@@ -376,6 +376,8 @@ static void __kvmi_unhook(struct kvm *kvm)
struct kvm_introspection *kvmi = KVMI(kvm);
wait_for_completion_killable(&kvm->kvmi_complete);
+
+ kvmi_arch_unhook(kvm);
kvmi_sock_put(kvmi);
}
@@ -423,6 +425,8 @@ static int __kvmi_hook(struct kvm *kvm,
if (!kvmi_sock_get(kvmi, hook->fd))
return -EINVAL;
+ kvmi_arch_hook(kvm);
+
return 0;
}
@@ -1055,3 +1059,115 @@ int kvmi_set_gfn_access(struct kvm *kvm, gfn_t gfn, u8
access)
return err;
}
+
+static int kvmi_get_gfn_access(struct kvm_introspection *kvmi, const gfn_t gfn,
+ u8 *access)
+{
+ struct kvmi_mem_access *m;
+
+ read_lock(&kvmi->access_tree_lock);
+ m = __kvmi_get_gfn_access(kvmi, gfn);
+ if (m)
+ *access = m->access;
+ read_unlock(&kvmi->access_tree_lock);
+
+ return m ? 0 : -1;
+}
+
+static bool kvmi_restricted_page_access(struct kvm_introspection *kvmi,
+ gpa_t gpa, u8 access)
+{
+ u8 allowed_access;
+ int err;
+
+ err = kvmi_get_gfn_access(kvmi, gpa_to_gfn(gpa), &allowed_access);
+ if (err)
+ return false;
+
+ /*
+ * We want to be notified only for violations involving access
+ * bits that we've specifically cleared
+ */
+ if (access & (~allowed_access))
+ return true;
+
+ return false;
+}
+
+bool kvmi_pf_event(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva, u8 access)
+{
+ bool ret = false;
+ u32 action;
+
+ if (!kvmi_restricted_page_access(KVMI(vcpu->kvm), gpa, access))
+ return true;
+
+ action = kvmi_msg_send_vcpu_pf(vcpu, gpa, gva, access);
+ switch (action) {
+ case KVMI_EVENT_ACTION_CONTINUE:
+ ret = true;
+ break;
+ case KVMI_EVENT_ACTION_RETRY:
+ break;
+ default:
+ kvmi_handle_common_event_actions(vcpu, action);
+ }
+
+ return ret;
+}
+
+void kvmi_add_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
+ unsigned long npages)
+{
+ struct kvm_introspection *kvmi = KVMI(kvm);
+ gfn_t start = slot->base_gfn;
+ gfn_t end = start + npages;
+ int idx;
+
+ idx = srcu_read_lock(&kvm->srcu);
+ spin_lock(&kvm->mmu_lock);
+ read_lock(&kvmi->access_tree_lock);
+
+ while (start < end) {
+ struct kvmi_mem_access *m;
+
+ m = __kvmi_get_gfn_access(kvmi, start);
+ if (m)
+ kvmi_arch_update_page_tracking(kvm, slot, m);
+ start++;
+ }
+
+ read_unlock(&kvmi->access_tree_lock);
+ spin_unlock(&kvm->mmu_lock);
+ srcu_read_unlock(&kvm->srcu, idx);
+}
+
+void kvmi_remove_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+ struct kvm_introspection *kvmi = KVMI(kvm);
+ gfn_t start = slot->base_gfn;
+ gfn_t end = start + slot->npages;
+ int idx;
+
+ idx = srcu_read_lock(&kvm->srcu);
+ spin_lock(&kvm->mmu_lock);
+ write_lock(&kvmi->access_tree_lock);
+
+ while (start < end) {
+ struct kvmi_mem_access *m;
+
+ m = __kvmi_get_gfn_access(kvmi, start);
+ if (m) {
+ u8 prev_access = m->access;
+
+ m->access = full_access;
+ kvmi_arch_update_page_tracking(kvm, slot, m);
+ m->access = prev_access;
+ }
+ start++;
+ }
+
+ write_unlock(&kvmi->access_tree_lock);
+ spin_unlock(&kvm->mmu_lock);
+ srcu_read_unlock(&kvm->srcu, idx);
+}
diff --git a/virt/kvm/introspection/kvmi_int.h
b/virt/kvm/introspection/kvmi_int.h
index 41720b194458..bf6545e66425 100644
--- a/virt/kvm/introspection/kvmi_int.h
+++ b/virt/kvm/introspection/kvmi_int.h
@@ -63,6 +63,7 @@ int kvmi_msg_vcpu_reply(const struct kvmi_vcpu_msg_job *job,
u32 kvmi_msg_send_vcpu_pause(struct kvm_vcpu *vcpu);
u32 kvmi_msg_send_vcpu_hypercall(struct kvm_vcpu *vcpu);
u32 kvmi_msg_send_vcpu_bp(struct kvm_vcpu *vcpu, u64 gpa, u8 insn_len);
+u32 kvmi_msg_send_vcpu_pf(struct kvm_vcpu *vcpu, u64 gpa, u64 gva, u8 access);
/* kvmi.c */
void *kvmi_msg_alloc(void);
@@ -93,6 +94,10 @@ int kvmi_cmd_write_physical(struct kvm *kvm, u64 gpa, size_t
size,
const void *buf);
int kvmi_cmd_vcpu_pause(struct kvm_vcpu *vcpu, bool wait);
int kvmi_set_gfn_access(struct kvm *kvm, gfn_t gfn, u8 access);
+bool kvmi_pf_event(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva, u8 access);
+void kvmi_add_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
+ unsigned long npages);
+void kvmi_remove_memslot(struct kvm *kvm, struct kvm_memory_slot *slot);
/* arch */
void kvmi_arch_init_vcpu_events_mask(unsigned long *supported);
@@ -114,5 +119,7 @@ void kvmi_arch_send_pending_event(struct kvm_vcpu *vcpu);
void kvmi_arch_update_page_tracking(struct kvm *kvm,
struct kvm_memory_slot *slot,
struct kvmi_mem_access *m);
+void kvmi_arch_hook(struct kvm *kvm);
+void kvmi_arch_unhook(struct kvm *kvm);
#endif
diff --git a/virt/kvm/introspection/kvmi_msg.c
b/virt/kvm/introspection/kvmi_msg.c
index 2cba745db7e3..1388b5c768af 100644
--- a/virt/kvm/introspection/kvmi_msg.c
+++ b/virt/kvm/introspection/kvmi_msg.c
@@ -875,3 +875,22 @@ u32 kvmi_msg_send_vcpu_bp(struct kvm_vcpu *vcpu, u64 gpa,
u8 insn_len)
return action;
}
+
+u32 kvmi_msg_send_vcpu_pf(struct kvm_vcpu *vcpu, u64 gpa, u64 gva, u8 access)
+{
+ struct kvmi_vcpu_event_pf e;
+ u32 action;
+ int err;
+
+ memset(&e, 0, sizeof(e));
+ e.gpa = gpa;
+ e.gva = gva;
+ e.access = access;
+
+ err = kvmi_send_vcpu_event(vcpu, KVMI_VCPU_EVENT_PF, &e, sizeof(e),
+ NULL, 0, &action);
+ if (err)
+ return KVMI_EVENT_ACTION_CONTINUE;
+
+ return action;
+}
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