From: Nicușor Cîțu <nicu.c...@icloud.com>
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 <nicu.c...@icloud.com>
Co-developed-by: Adalbert Lazăr <ala...@bitdefender.com>
Signed-off-by: Adalbert Lazăr <ala...@bitdefender.com>
---
Documentation/virt/kvm/kvmi.rst | 43 +++++++++++
arch/x86/include/asm/kvmi_host.h | 3 +
arch/x86/include/uapi/asm/kvmi.h | 13 ++++
arch/x86/kvm/kvmi.c | 58 ++++++++++++++
arch/x86/kvm/kvmi.h | 1 +
arch/x86/kvm/kvmi_msg.c | 19 +++++
arch/x86/kvm/svm/svm.c | 35 +++++++++
arch/x86/kvm/vmx/vmx.c | 21 ++++++
include/uapi/linux/kvmi.h | 1 +
.../testing/selftests/kvm/x86_64/kvmi_test.c | 75 +++++++++++++++++++
10 files changed, 269 insertions(+)
diff --git a/Documentation/virt/kvm/kvmi.rst b/Documentation/virt/kvm/kvmi.rst
index d60a69e00e0f..e24a93e93fe8 100644
--- a/Documentation/virt/kvm/kvmi.rst
+++ b/Documentation/virt/kvm/kvmi.rst
@@ -540,6 +540,7 @@ the following events::
KVMI_VCPU_EVENT_BREAKPOINT
KVMI_VCPU_EVENT_CR
+ KVMI_VCPU_EVENT_DESCRIPTOR
KVMI_VCPU_EVENT_HYPERCALL
KVMI_VCPU_EVENT_XSETBV
@@ -563,6 +564,8 @@ the *KVMI_VM_CONTROL_EVENTS* command.
* -KVM_EINVAL - the event ID is unknown (use *KVMI_VM_CHECK_EVENT* first)
* -KVM_EPERM - the access is disallowed (use *KVMI_VM_CHECK_EVENT* first)
* -KVM_EAGAIN - the selected vCPU can't be introspected yet
+* -KVM_EOPNOTSUPP - the event can't be intercepted in the current setup
+ (e.g. KVMI_VCPU_EVENT_DESCRIPTOR with AMD)
* -KVM_EBUSY - the event can't be intercepted right now
(e.g. KVMI_VCPU_EVENT_BREAKPOINT if the #BP event
is already intercepted by userspace)
@@ -1198,3 +1201,43 @@ to be changed and the introspection has been enabled for
this event
``kvmi_vcpu_event`` (with the vCPU state), the extended control register
number (``xcr``), the old value (``old_value``) and the new value
(``new_value``) are sent to the introspection tool.
+
+8. KVMI_VCPU_EVENT_DESCRIPTOR
+-----------------------------
+
+:Architectures: x86
+:Versions: >= 1
+:Actions: CONTINUE, RETRY, CRASH
+:Parameters:
+
+::
+
+ struct kvmi_vcpu_event;
+ struct kvmi_vcpu_event_descriptor {
+ __u8 descriptor;
+ __u8 write;
+ __u8 padding[6];
+ };
+
+:Returns:
+
+::
+
+ struct kvmi_vcpu_hdr;
+ struct kvmi_vcpu_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_vcpu_event`` (with the vCPU state), the descriptor-table register
+(``descriptor``) and the access type (``write``) 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 d66349208a6b..a24ba87036f7 100644
--- a/arch/x86/include/asm/kvmi_host.h
+++ b/arch/x86/include/asm/kvmi_host.h
@@ -48,6 +48,7 @@ bool kvmi_monitor_cr3w_intercept(struct kvm_vcpu *vcpu, bool
enable);
void kvmi_enter_guest(struct kvm_vcpu *vcpu);
void kvmi_xsetbv_event(struct kvm_vcpu *vcpu, u8 xcr,
u64 old_value, u64 new_value);
+bool kvmi_descriptor_event(struct kvm_vcpu *vcpu, u8 descriptor, bool write);
#else /* CONFIG_KVM_INTROSPECTION */
@@ -63,6 +64,8 @@ static inline bool kvmi_monitor_cr3w_intercept(struct
kvm_vcpu *vcpu,
static inline void kvmi_enter_guest(struct kvm_vcpu *vcpu) { }
static inline void kvmi_xsetbv_event(struct kvm_vcpu *vcpu, u8 xcr,
u64 old_value, u64 new_value) { }
+static inline bool kvmi_descriptor_event(struct kvm_vcpu *vcpu, u8 descriptor,
+ bool 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 7b93450d0d62..9c608ef5daa3 100644
--- a/arch/x86/include/uapi/asm/kvmi.h
+++ b/arch/x86/include/uapi/asm/kvmi.h
@@ -128,4 +128,17 @@ struct kvmi_vcpu_get_mtrr_type_reply {
__u8 padding[7];
};
+enum {
+ KVMI_DESC_IDTR = 1,
+ KVMI_DESC_GDTR = 2,
+ KVMI_DESC_LDTR = 3,
+ KVMI_DESC_TR = 4,
+};
+
+struct kvmi_vcpu_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 d34f5f03a56f..cf7167366214 100644
--- a/arch/x86/kvm/kvmi.c
+++ b/arch/x86/kvm/kvmi.c
@@ -15,6 +15,7 @@ void kvmi_arch_init_vcpu_events_mask(unsigned long *supported)
set_bit(KVMI_VCPU_EVENT_BREAKPOINT, supported);
set_bit(KVMI_VCPU_EVENT_CR, supported);
set_bit(KVMI_VCPU_EVENT_HYPERCALL, supported);
+ set_bit(KVMI_VCPU_EVENT_DESCRIPTOR, supported);
set_bit(KVMI_VCPU_EVENT_TRAP, supported);
set_bit(KVMI_VCPU_EVENT_XSETBV, supported);
}
@@ -285,6 +286,21 @@ 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 (!static_call(kvm_x86_desc_ctrl_supported)())
+ return -KVM_EOPNOTSUPP;
+
+ static_call(kvm_x86_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)
{
@@ -294,6 +310,9 @@ int kvmi_arch_cmd_control_intercept(struct kvm_vcpu *vcpu,
case KVMI_VCPU_EVENT_BREAKPOINT:
err = kvmi_control_bp_intercept(vcpu, enable);
break;
+ case KVMI_VCPU_EVENT_DESCRIPTOR:
+ err = kvmi_control_desc_intercept(vcpu, enable);
+ break;
default:
break;
}
@@ -325,6 +344,7 @@ static void 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);
}
bool kvmi_arch_clean_up_interception(struct kvm_vcpu *vcpu)
@@ -597,3 +617,41 @@ void kvmi_xsetbv_event(struct kvm_vcpu *vcpu, u8 xcr,
kvmi_put(vcpu->kvm);
}
+
+static bool __kvmi_descriptor_event(struct kvm_vcpu *vcpu, u8 descriptor,
+ bool write)
+{
+ bool ret = false;
+ u32 action;
+
+ action = kvmi_msg_send_vcpu_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, action);
+ }
+
+ return ret;
+}
+
+bool kvmi_descriptor_event(struct kvm_vcpu *vcpu, u8 descriptor, bool write)
+{
+ 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_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/kvmi.h b/arch/x86/kvm/kvmi.h
index 43bc956d740c..92422e2e57cf 100644
--- a/arch/x86/kvm/kvmi.h
+++ b/arch/x86/kvm/kvmi.h
@@ -16,5 +16,6 @@ u32 kvmi_msg_send_vcpu_cr(struct kvm_vcpu *vcpu, u32 cr, u64
old_value,
u32 kvmi_msg_send_vcpu_trap(struct kvm_vcpu *vcpu);
u32 kvmi_msg_send_vcpu_xsetbv(struct kvm_vcpu *vcpu, u8 xcr,
u64 old_value, u64 new_value);
+u32 kvmi_msg_send_vcpu_descriptor(struct kvm_vcpu *vcpu, u8 desc, bool write);
#endif
diff --git a/arch/x86/kvm/kvmi_msg.c b/arch/x86/kvm/kvmi_msg.c
index c890c2396fbc..b74df3fc832d 100644
--- a/arch/x86/kvm/kvmi_msg.c
+++ b/arch/x86/kvm/kvmi_msg.c
@@ -330,3 +330,22 @@ u32 kvmi_msg_send_vcpu_xsetbv(struct kvm_vcpu *vcpu, u8
xcr,
return action;
}
+
+u32 kvmi_msg_send_vcpu_descriptor(struct kvm_vcpu *vcpu, u8 desc, bool write)
+{
+ struct kvmi_vcpu_event_descriptor e;
+ u32 action;
+ int err;
+
+ memset(&e, 0, sizeof(e));
+ e.descriptor = desc;
+ e.write = write ? 1 : 0;
+
+ err = kvmi_send_vcpu_event(vcpu, KVMI_VCPU_EVENT_DESCRIPTOR,
+ &e, sizeof(e), NULL, 0, &action);
+ if (err)
+ action = KVMI_EVENT_ACTION_CONTINUE;
+
+ return action;
+
+}
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 7353996907d3..98b4909254a0 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2642,6 +2642,41 @@ static int emulate_on_interception(struct kvm_vcpu *vcpu)
static int descriptor_access_interception(struct kvm_vcpu *vcpu)
{
+ struct vcpu_svm *svm = to_svm(vcpu);
+
+#ifdef CONFIG_KVM_INTROSPECTION
+ struct vmcb_control_area *c = &svm->vmcb->control;
+ bool cont;
+
+ switch (c->exit_code) {
+ case SVM_EXIT_IDTR_READ:
+ case SVM_EXIT_IDTR_WRITE:
+ cont = 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:
+ cont = 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:
+ cont = 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:
+ cont = kvmi_descriptor_event(vcpu, KVMI_DESC_TR,
+ c->exit_code == SVM_EXIT_TR_WRITE);
+ break;
+ default:
+ cont = true;
+ break;
+ }
+ if (!cont)
+ return 1;
+#endif /* CONFIG_KVM_INTROSPECTION */
+
return kvm_emulate_instruction(vcpu, 0);
}
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c268194cee84..58a753b1ba41 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5068,7 +5068,28 @@ static int handle_set_cr4(struct kvm_vcpu *vcpu,
unsigned long val)
static int handle_desc(struct kvm_vcpu *vcpu)
{
+#ifdef CONFIG_KVM_INTROSPECTION
+ u32 vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
+ u8 store = (vmx_instruction_info >> 29) & 0x1;
+ u8 descriptor = 0;
+
+ if (to_vmx(vcpu)->exit_reason.basic == 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;
+ }
+
+ if (!kvmi_descriptor_event(vcpu, descriptor, store))
+ return 1;
+#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 a48cf2c1f9a7..aa257b011ff1 100644
--- a/include/uapi/linux/kvmi.h
+++ b/include/uapi/linux/kvmi.h
@@ -67,6 +67,7 @@ enum {
KVMI_VCPU_EVENT_CR = KVMI_VCPU_EVENT_ID(3),
KVMI_VCPU_EVENT_TRAP = KVMI_VCPU_EVENT_ID(4),
KVMI_VCPU_EVENT_XSETBV = KVMI_VCPU_EVENT_ID(5),
+ KVMI_VCPU_EVENT_DESCRIPTOR = KVMI_VCPU_EVENT_ID(6),
KVMI_NEXT_VCPU_EVENT
};
diff --git a/tools/testing/selftests/kvm/x86_64/kvmi_test.c
b/tools/testing/selftests/kvm/x86_64/kvmi_test.c
index 231d574ed592..c1ce163bc3c4 100644
--- a/tools/testing/selftests/kvm/x86_64/kvmi_test.c
+++ b/tools/testing/selftests/kvm/x86_64/kvmi_test.c
@@ -58,6 +58,7 @@ enum {
GUEST_TEST_NOOP = 0,
GUEST_TEST_BP,
GUEST_TEST_CR,
+ GUEST_TEST_DESCRIPTOR,
GUEST_TEST_HYPERCALL,
GUEST_TEST_XSETBV,
};
@@ -87,6 +88,14 @@ 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");
@@ -146,6 +155,9 @@ 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;
@@ -1494,6 +1506,68 @@ static void test_cmd_vcpu_get_mtrr_type(struct kvm_vm
*vm)
pr_debug("mtrr_type: gpa 0x%lx type 0x%x\n", test_gpa, rpl.type);
}
+static void test_desc_read_access(__u16 event_id)
+{
+ struct kvmi_msg_hdr hdr;
+ struct {
+ struct vcpu_event vcpu_ev;
+ struct kvmi_vcpu_event_descriptor desc;
+ } ev;
+ struct vcpu_reply rpl = {};
+
+ receive_vcpu_event(&hdr, &ev.vcpu_ev, sizeof(ev), event_id);
+
+ pr_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.vcpu_ev, KVMI_EVENT_ACTION_CONTINUE,
+ &rpl, sizeof(rpl));
+}
+
+static void test_desc_write_access(__u16 event_id)
+{
+ struct kvmi_msg_hdr hdr;
+ struct {
+ struct vcpu_event vcpu_ev;
+ struct kvmi_vcpu_event_descriptor desc;
+ } ev;
+ struct vcpu_reply rpl = {};
+
+ receive_vcpu_event(&hdr, &ev.vcpu_ev, sizeof(ev), event_id);
+
+ pr_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.vcpu_ev, KVMI_EVENT_ACTION_CONTINUE,
+ &rpl, sizeof(rpl));
+}
+
+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,
+ };
+ __u16 event_id = KVMI_VCPU_EVENT_DESCRIPTOR;
+ pthread_t vcpu_thread;
+
+ enable_vcpu_event(vm, event_id);
+ vcpu_thread = start_vcpu_worker(&data);
+
+ test_desc_read_access(event_id);
+ test_desc_write_access(event_id);
+
+ wait_vcpu_worker(vcpu_thread);
+ disable_vcpu_event(vm, event_id);
+}
+
static void test_introspection(struct kvm_vm *vm)
{
srandom(time(0));
@@ -1523,6 +1597,7 @@ static void test_introspection(struct kvm_vm *vm)
test_cmd_vcpu_get_xcr(vm);
test_cmd_vcpu_xsave(vm);
test_cmd_vcpu_get_mtrr_type(vm);
+ test_event_descriptor(vm);
unhook_introspection(vm);
}
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