From: Nicușor Cîțu <ncitu@xxxxxxxxxxxxxxx>
This event is sent when IDTR, GDTR, LDTR or TR are accessed.
These could be used to implement a tiny agent which runs in the context
of an introspected guest and uses virtualized exceptions (#VE) and
alternate EPT views (VMFUNC #0) to filter converted VMEXITS. The events
of interested will be suppressed (after some appropriate guest-side
handling) while the rest will be sent to the introspector via a VMCALL.
Signed-off-by: Nicușor Cîțu <ncitu@xxxxxxxxxxxxxxx>
Co-developed-by: Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>
Signed-off-by: Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>
---
Documentation/virt/kvm/kvmi.rst | 39 ++++++++++++
arch/x86/include/asm/kvmi_host.h | 3 +
arch/x86/include/uapi/asm/kvmi.h | 11 ++++
arch/x86/kvm/kvmi.c | 57 ++++++++++++++++++
arch/x86/kvm/svm.c | 45 ++++++++++++++
arch/x86/kvm/vmx/vmx.c | 37 +++++++++++-
include/uapi/linux/kvmi.h | 1 +
.../testing/selftests/kvm/x86_64/kvmi_test.c | 60 +++++++++++++++++++
virt/kvm/introspection/kvmi_int.h | 2 +
virt/kvm/introspection/kvmi_msg.c | 17 ++++++
10 files changed, 270 insertions(+), 2 deletions(-)
diff --git a/Documentation/virt/kvm/kvmi.rst b/Documentation/virt/kvm/kvmi.rst
index ae8e242c4721..0a0e5305a0af 100644
--- a/Documentation/virt/kvm/kvmi.rst
+++ b/Documentation/virt/kvm/kvmi.rst
@@ -532,6 +532,7 @@ the following events::
KVMI_EVENT_BREAKPOINT
KVMI_EVENT_CR
+ KVMI_EVENT_DESCRIPTOR
KVMI_EVENT_HYPERCALL
KVMI_EVENT_TRAP
KVMI_EVENT_XSETBV
@@ -1088,3 +1089,41 @@ to be changed and the introspection has been enabled for this event
(see *KVMI_VCPU_CONTROL_EVENTS*).
``kvmi_event`` is sent to the introspection tool.
+
+8. KVMI_EVENT_DESCRIPTOR
+------------------------
+
+:Architecture: x86
+:Versions: >= 1
+:Actions: CONTINUE, RETRY, CRASH
+:Parameters:
+
+::
+
+ struct kvmi_event;
+ struct kvmi_event_descriptor {
+ __u8 descriptor;
+ __u8 write;
+ __u8 padding[6];
+ };
+
+:Returns:
+
+::
+
+ struct kvmi_vcpu_hdr;
+ struct kvmi_event_reply;
+
+This event is sent when a descriptor table register is accessed and the
+introspection has been enabled for this event (see **KVMI_VCPU_CONTROL_EVENTS**).
+
+``kvmi_event`` and ``kvmi_event_descriptor`` are sent to the introspection tool.
+
+``descriptor`` can be one of::
+
+ KVMI_DESC_IDTR
+ KVMI_DESC_GDTR
+ KVMI_DESC_LDTR
+ KVMI_DESC_TR
+
+``write`` is 1 if the descriptor was written, 0 otherwise.
diff --git a/arch/x86/include/asm/kvmi_host.h b/arch/x86/include/asm/kvmi_host.h
index b3fa950362db..8f9e6bd2953a 100644
--- a/arch/x86/include/asm/kvmi_host.h
+++ b/arch/x86/include/asm/kvmi_host.h
@@ -31,6 +31,7 @@ bool kvmi_cr_event(struct kvm_vcpu *vcpu, unsigned int cr,
bool kvmi_cr3_intercepted(struct kvm_vcpu *vcpu);
bool kvmi_monitor_cr3w_intercept(struct kvm_vcpu *vcpu, bool enable);
void kvmi_xsetbv_event(struct kvm_vcpu *vcpu);
+bool kvmi_descriptor_event(struct kvm_vcpu *vcpu, u8 descriptor, u8 write);
#else /* CONFIG_KVM_INTROSPECTION */
@@ -43,6 +44,8 @@ static inline bool kvmi_cr3_intercepted(struct kvm_vcpu *vcpu) { return false; }
static inline bool kvmi_monitor_cr3w_intercept(struct kvm_vcpu *vcpu,
bool enable) { return false; }
static inline void kvmi_xsetbv_event(struct kvm_vcpu *vcpu) { }
+static inline bool kvmi_descriptor_event(struct kvm_vcpu *vcpu, u8 descriptor,
+ u8 write) { return true; }
#endif /* CONFIG_KVM_INTROSPECTION */
diff --git a/arch/x86/include/uapi/asm/kvmi.h b/arch/x86/include/uapi/asm/kvmi.h
index 1dc3fc02d3ec..6f411b9ba449 100644
--- a/arch/x86/include/uapi/asm/kvmi.h
+++ b/arch/x86/include/uapi/asm/kvmi.h
@@ -110,4 +110,15 @@ struct kvmi_vcpu_get_mtrr_type_reply {
__u8 padding[7];
};
+#define KVMI_DESC_IDTR 1
+#define KVMI_DESC_GDTR 2
+#define KVMI_DESC_LDTR 3
+#define KVMI_DESC_TR 4
+
+struct kvmi_event_descriptor {
+ __u8 descriptor;
+ __u8 write;
+ __u8 padding[6];
+};
+
#endif /* _UAPI_ASM_X86_KVMI_H */
diff --git a/arch/x86/kvm/kvmi.c b/arch/x86/kvm/kvmi.c
index d3cddd34326b..ed9b45060e2a 100644
--- a/arch/x86/kvm/kvmi.c
+++ b/arch/x86/kvm/kvmi.c
@@ -311,6 +311,21 @@ static void kvmi_arch_disable_cr3w_intercept(struct kvm_vcpu *vcpu)
vcpu->arch.kvmi->cr3w.kvm_intercepted = false;
}
+static int kvmi_control_desc_intercept(struct kvm_vcpu *vcpu, bool enable)
+{
+ if (!kvm_x86_ops->umip_emulated())
+ return -KVM_EOPNOTSUPP;
+
+ kvm_x86_ops->control_desc_intercept(vcpu, enable);
+
+ return 0;
+}
+
+static void kvmi_arch_disable_desc_intercept(struct kvm_vcpu *vcpu)
+{
+ kvmi_control_desc_intercept(vcpu, false);
+}
+
int kvmi_arch_cmd_control_intercept(struct kvm_vcpu *vcpu,
unsigned int event_id, bool enable)
{
@@ -320,6 +335,9 @@ int kvmi_arch_cmd_control_intercept(struct kvm_vcpu *vcpu,
case KVMI_EVENT_BREAKPOINT:
err = kvmi_control_bp_intercept(vcpu, enable);
break;
+ case KVMI_EVENT_DESCRIPTOR:
+ err = kvmi_control_desc_intercept(vcpu, enable);
+ break;
default:
break;
}
@@ -356,6 +374,7 @@ bool kvmi_arch_restore_interception(struct kvm_vcpu *vcpu)
kvmi_arch_disable_bp_intercept(vcpu);
kvmi_arch_disable_cr3w_intercept(vcpu);
+ kvmi_arch_disable_desc_intercept(vcpu);
return true;
}
@@ -644,3 +663,41 @@ int kvmi_arch_cmd_vcpu_get_mtrr_type(struct kvm_vcpu *vcpu, u64 gpa, u8 *type)
return 0;
}
+
+static bool __kvmi_descriptor_event(struct kvm_vcpu *vcpu, u8 descriptor,
+ u8 write)
+{
+ bool ret = false;
+ u32 action;
+
+ action = kvmi_msg_send_descriptor(vcpu, descriptor, write);
+ switch (action) {
+ case KVMI_EVENT_ACTION_CONTINUE:
+ ret = true;
+ break;
+ case KVMI_EVENT_ACTION_RETRY:
+ break;
+ default:
+ kvmi_handle_common_event_actions(vcpu->kvm, action, "DESC");
+ }
+
+ return ret;
+}
+
+bool kvmi_descriptor_event(struct kvm_vcpu *vcpu, u8 descriptor, u8 write)
+{
+ struct kvm_introspection *kvmi;
+ bool ret = true;
+
+ kvmi = kvmi_get(vcpu->kvm);
+ if (!kvmi)
+ return true;
+
+ if (is_event_enabled(vcpu, KVMI_EVENT_DESCRIPTOR))
+ ret = __kvmi_descriptor_event(vcpu, descriptor, write);
+
+ kvmi_put(vcpu->kvm);
+
+ return ret;
+}
+EXPORT_SYMBOL(kvmi_descriptor_event);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 909308711bb7..988eb6937515 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -4808,6 +4808,41 @@ static int avic_unaccelerated_access_interception(struct vcpu_svm *svm)
return ret;
}
+#ifdef CONFIG_KVM_INTROSPECTION
+static int descriptor_access_interception(struct vcpu_svm *svm)
+{
+ struct kvm_vcpu *vcpu = &svm->vcpu;
+ struct vmcb_control_area *c = &svm->vmcb->control;
+
+ switch (c->exit_code) {
+ case SVM_EXIT_IDTR_READ:
+ case SVM_EXIT_IDTR_WRITE:
+ kvmi_descriptor_event(vcpu, KVMI_DESC_IDTR,
+ c->exit_code == SVM_EXIT_IDTR_WRITE);
+ break;
+ case SVM_EXIT_GDTR_READ:
+ case SVM_EXIT_GDTR_WRITE:
+ kvmi_descriptor_event(vcpu, KVMI_DESC_GDTR,
+ c->exit_code == SVM_EXIT_GDTR_WRITE);
+ break;
+ case SVM_EXIT_LDTR_READ:
+ case SVM_EXIT_LDTR_WRITE:
+ kvmi_descriptor_event(vcpu, KVMI_DESC_LDTR,
+ c->exit_code == SVM_EXIT_LDTR_WRITE);
+ break;
+ case SVM_EXIT_TR_READ:
+ case SVM_EXIT_TR_WRITE:
+ kvmi_descriptor_event(vcpu, KVMI_DESC_TR,
+ c->exit_code == SVM_EXIT_TR_WRITE);
+ break;
+ default:
+ break;
+ }
+
+ return kvm_emulate_instruction(vcpu, 0);
+}
+#endif /* CONFIG_KVM_INTROSPECTION */
+
static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = {
[SVM_EXIT_READ_CR0] = cr_interception,
[SVM_EXIT_READ_CR3] = cr_interception,
@@ -4874,6 +4909,16 @@ static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = {
[SVM_EXIT_RSM] = rsm_interception,
[SVM_EXIT_AVIC_INCOMPLETE_IPI] = avic_incomplete_ipi_interception,
[SVM_EXIT_AVIC_UNACCELERATED_ACCESS] = avic_unaccelerated_access_interception,
+#ifdef CONFIG_KVM_INTROSPECTION
+ [SVM_EXIT_IDTR_READ] = descriptor_access_interception,
+ [SVM_EXIT_GDTR_READ] = descriptor_access_interception,
+ [SVM_EXIT_LDTR_READ] = descriptor_access_interception,
+ [SVM_EXIT_TR_READ] = descriptor_access_interception,
+ [SVM_EXIT_IDTR_WRITE] = descriptor_access_interception,
+ [SVM_EXIT_GDTR_WRITE] = descriptor_access_interception,
+ [SVM_EXIT_LDTR_WRITE] = descriptor_access_interception,
+ [SVM_EXIT_TR_WRITE] = descriptor_access_interception,
+#endif /* CONFIG_KVM_INTROSPECTION */
};
static void dump_vmcb(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 157dfc3f756a..68986f600f98 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -3070,11 +3070,11 @@ int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
if (!boot_cpu_has(X86_FEATURE_UMIP) && vmx_umip_emulated()) {
if (cr4 & X86_CR4_UMIP) {
- secondary_exec_controls_setbit(vmx, SECONDARY_EXEC_DESC);
+ vmx_control_desc_intercept(vcpu, true);
hw_cr4 &= ~X86_CR4_UMIP;
} else if (!is_guest_mode(vcpu) ||
!nested_cpu_has2(get_vmcs12(vcpu), SECONDARY_EXEC_DESC)) {
- secondary_exec_controls_clearbit(vmx, SECONDARY_EXEC_DESC);
+ vmx_control_desc_intercept(vcpu, false);
}
}
@@ -4831,7 +4831,40 @@ static int handle_set_cr4(struct kvm_vcpu *vcpu, unsigned long val)
static int handle_desc(struct kvm_vcpu *vcpu)
{
+#ifdef CONFIG_KVM_INTROSPECTION
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+ u32 exit_reason = vmx->exit_reason;
+ u32 vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
+ u8 store = (vmx_instruction_info >> 29) & 0x1;
+ u8 descriptor = 0;
+
+ if (exit_reason == EXIT_REASON_GDTR_IDTR) {
+ if ((vmx_instruction_info >> 28) & 0x1)
+ descriptor = KVMI_DESC_IDTR;
+ else
+ descriptor = KVMI_DESC_GDTR;
+ } else {
+ if ((vmx_instruction_info >> 28) & 0x1)
+ descriptor = KVMI_DESC_TR;
+ else
+ descriptor = KVMI_DESC_LDTR;
+ }
+
+ /*
+ * For now, this function returns false only when the guest
+ * is ungracefully stopped (crashed) or the current instruction
+ * is skipped by the introspection tool.
+ */
+ if (!kvmi_descriptor_event(vcpu, descriptor, store))
+ return 1;
+
+ /*
+ * We are here because X86_CR4_UMIP was set or
+ * KVMI enabled the interception.
+ */
+#else
WARN_ON(!(vcpu->arch.cr4 & X86_CR4_UMIP));
+#endif /* CONFIG_KVM_INTROSPECTION */
return kvm_emulate_instruction(vcpu, 0);
}
diff --git a/include/uapi/linux/kvmi.h b/include/uapi/linux/kvmi.h
index 5e911ca7a636..a8f5dc415e3d 100644
--- a/include/uapi/linux/kvmi.h
+++ b/include/uapi/linux/kvmi.h
@@ -51,6 +51,7 @@ enum {
KVMI_EVENT_CR = 4,
KVMI_EVENT_TRAP = 5,
KVMI_EVENT_XSETBV = 6,
+ KVMI_EVENT_DESCRIPTOR = 7,
KVMI_NUM_EVENTS
};
diff --git a/tools/testing/selftests/kvm/x86_64/kvmi_test.c b/tools/testing/selftests/kvm/x86_64/kvmi_test.c
index 600d65922bf4..4308cb995ce3 100644
--- a/tools/testing/selftests/kvm/x86_64/kvmi_test.c
+++ b/tools/testing/selftests/kvm/x86_64/kvmi_test.c
@@ -54,6 +54,7 @@ enum {
GUEST_TEST_NOOP = 0,
GUEST_TEST_BP,
GUEST_TEST_CR,
+ GUEST_TEST_DESCRIPTOR,
GUEST_TEST_HYPERCALL,
GUEST_TEST_XSETBV,
};
@@ -79,6 +80,14 @@ static void guest_cr_test(void)
set_cr4(get_cr4() | X86_CR4_OSXSAVE);
}
+static void guest_descriptor_test(void)
+{
+ void *ptr;
+
+ asm volatile("sgdt %0" :: "m"(ptr));
+ asm volatile("lgdt %0" :: "m"(ptr));
+}
+
static void guest_hypercall_test(void)
{
asm volatile("mov $34, %rax");
@@ -138,6 +147,9 @@ static void guest_code(void)
case GUEST_TEST_CR:
guest_cr_test();
break;
+ case GUEST_TEST_DESCRIPTOR:
+ guest_descriptor_test();
+ break;
case GUEST_TEST_HYPERCALL:
guest_hypercall_test();
break;
@@ -1360,6 +1372,53 @@ static void test_cmd_vcpu_get_mtrr_type(struct kvm_vm *vm)
DEBUG("mtrr_type: gpa 0x%lx type 0x%x\n", test_gpa, rpl.type);
}
+static void test_event_descriptor(struct kvm_vm *vm)
+{
+ struct vcpu_worker_data data = {
+ .vm = vm,
+ .vcpu_id = VCPU_ID,
+ .test_id = GUEST_TEST_DESCRIPTOR,
+ };
+ struct kvmi_msg_hdr hdr;
+ struct {
+ struct kvmi_event common;
+ struct kvmi_event_descriptor desc;
+ } ev;
+ struct vcpu_reply rpl = {};
+ __u16 event_id = KVMI_EVENT_DESCRIPTOR;
+ pthread_t vcpu_thread;
+
+ enable_vcpu_event(vm, event_id);
+
+ vcpu_thread = start_vcpu_worker(&data);
+
+ receive_event(&hdr, &ev.common, sizeof(ev), event_id);
+
+ DEBUG("Descriptor event (read), descriptor %u, write %u\n",
+ ev.desc.descriptor, ev.desc.write);
+
+ TEST_ASSERT(ev.desc.write == 0,
+ "Received a write descriptor access\n");
+
+ reply_to_event(&hdr, &ev.common, KVMI_EVENT_ACTION_CONTINUE,
+ &rpl, sizeof(rpl));
+
+ receive_event(&hdr, &ev.common, sizeof(ev), event_id);
+
+ DEBUG("Descriptor event (write), descriptor %u, write %u\n",
+ ev.desc.descriptor, ev.desc.write);
+
+ TEST_ASSERT(ev.desc.write == 1,
+ "Received a read descriptor access\n");
+
+ reply_to_event(&hdr, &ev.common, KVMI_EVENT_ACTION_CONTINUE,
+ &rpl, sizeof(rpl));
+
+ stop_vcpu_worker(vcpu_thread, &data);
+
+ disable_vcpu_event(vm, event_id);
+}
+
static void test_introspection(struct kvm_vm *vm)
{
setup_socket();
@@ -1387,6 +1446,7 @@ static void test_introspection(struct kvm_vm *vm)
test_event_xsetbv(vm);
test_cmd_vcpu_get_xsave(vm);
test_cmd_vcpu_get_mtrr_type(vm);
+ test_event_descriptor(vm);
unhook_introspection(vm);
}
diff --git a/virt/kvm/introspection/kvmi_int.h b/virt/kvm/introspection/kvmi_int.h
index 1e28355ea4d7..6d2c09a12c49 100644
--- a/virt/kvm/introspection/kvmi_int.h
+++ b/virt/kvm/introspection/kvmi_int.h
@@ -24,6 +24,7 @@
#define KVMI_KNOWN_VCPU_EVENTS ( \
BIT(KVMI_EVENT_BREAKPOINT) \
| BIT(KVMI_EVENT_CR) \
+ | BIT(KVMI_EVENT_DESCRIPTOR) \
| BIT(KVMI_EVENT_HYPERCALL) \
| BIT(KVMI_EVENT_TRAP) \
| BIT(KVMI_EVENT_PAUSE_VCPU) \
@@ -79,6 +80,7 @@ int kvmi_msg_send_unhook(struct kvm_introspection *kvmi);
u32 kvmi_msg_send_vcpu_pause(struct kvm_vcpu *vcpu);
u32 kvmi_msg_send_hypercall(struct kvm_vcpu *vcpu);
u32 kvmi_msg_send_bp(struct kvm_vcpu *vcpu, u64 gpa, u8 insn_len);
+u32 kvmi_msg_send_descriptor(struct kvm_vcpu *vcpu, u8 descriptor, u8 write);
/* kvmi.c */
void *kvmi_msg_alloc(void);
diff --git a/virt/kvm/introspection/kvmi_msg.c b/virt/kvm/introspection/kvmi_msg.c
index 6f23bc7517aa..fed483bec936 100644
--- a/virt/kvm/introspection/kvmi_msg.c
+++ b/virt/kvm/introspection/kvmi_msg.c
@@ -1029,3 +1029,20 @@ void kvmi_xsetbv_event(struct kvm_vcpu *vcpu)
kvmi_put(vcpu->kvm);
}
+
+u32 kvmi_msg_send_descriptor(struct kvm_vcpu *vcpu, u8 descriptor, u8 write)
+{
+ struct kvmi_event_descriptor e;
+ int err, action;
+
+ memset(&e, 0, sizeof(e));
+ e.descriptor = descriptor;
+ e.write = write;
+
+ err = kvmi_send_event(vcpu, KVMI_EVENT_DESCRIPTOR, &e, sizeof(e),
+ NULL, 0, &action);
+ if (err)
+ return KVMI_EVENT_ACTION_CONTINUE;
+
+ return action;
+}
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