From: Mihai Donțu <mdontu@xxxxxxxxxxxxxxx>
This event is sent on a specific user hypercall.
It is used by the code residing inside the introspected guest to call the
introspection tool and to report certain details about its operation.
For example, a classic antimalware remediation tool can report
what it has found during a scan.
Signed-off-by: Mihai Donțu <mdontu@xxxxxxxxxxxxxxx>
Co-developed-by: Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>
Signed-off-by: Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>
---
Documentation/virt/kvm/hypercalls.txt | 32 ++++++++++++++
Documentation/virt/kvm/kvmi.rst | 36 +++++++++++++++-
arch/x86/include/uapi/asm/kvmi.h | 2 +
arch/x86/kvm/kvmi.c | 33 ++++++++++++++
arch/x86/kvm/x86.c | 16 +++++--
include/linux/kvmi_host.h | 2 +
include/uapi/linux/kvm_para.h | 1 +
include/uapi/linux/kvmi.h | 1 +
.../testing/selftests/kvm/x86_64/kvmi_test.c | 43 +++++++++++++++++++
virt/kvm/introspection/kvmi.c | 22 ++++++++++
virt/kvm/introspection/kvmi_int.h | 13 +++++-
virt/kvm/introspection/kvmi_msg.c | 12 ++++++
12 files changed, 208 insertions(+), 5 deletions(-)
diff --git a/Documentation/virt/kvm/hypercalls.txt b/Documentation/virt/kvm/hypercalls.txt
index aff272bede08..c4f6cce1e4d3 100644
--- a/Documentation/virt/kvm/hypercalls.txt
+++ b/Documentation/virt/kvm/hypercalls.txt
@@ -152,3 +152,35 @@ a0: destination APIC ID
Usage example: When sending a call-function IPI-many to vCPUs, yield if
any of the IPI target vCPUs was preempted.
+
+9. KVM_HC_XEN_HVM_OP
+--------------------
+
+Architecture: x86
+Status: active
+Purpose: To enable communication between a guest agent and a VMI application
+Usage:
+
+An event will be sent to the VMI application (see kvmi.rst) if the following
+registers, which differ between 32bit and 64bit, have the following values:
+
+ 32bit 64bit value
+ ---------------------------
+ ebx (a0) rdi KVM_HC_XEN_HVM_OP_GUEST_REQUEST_VM_EVENT
+ ecx (a1) rsi 0
+
+This specification copies Xen's { __HYPERVISOR_hvm_op,
+HVMOP_guest_request_vm_event } hypercall and can originate from kernel or
+userspace.
+
+It returns 0 if successful, or a negative POSIX.1 error code if it fails. The
+absence of an active VMI application is not signaled in any way.
+
+The following registers are clobbered:
+
+ * 32bit: edx, esi, edi, ebp
+ * 64bit: rdx, r10, r8, r9
+
+In particular, for KVM_HC_XEN_HVM_OP_GUEST_REQUEST_VM_EVENT, the last two
+registers can be poisoned deliberately and cannot be used for passing
+information.
diff --git a/Documentation/virt/kvm/kvmi.rst b/Documentation/virt/kvm/kvmi.rst
index f9f961509c61..90256141a15d 100644
--- a/Documentation/virt/kvm/kvmi.rst
+++ b/Documentation/virt/kvm/kvmi.rst
@@ -527,7 +527,10 @@ Use *KVMI_VM_CHECK_EVENT* first.
struct kvmi_error_code
-Enables/disables vCPU introspection events.
+Enables/disables vCPU introspection events. This command can be used with
+the following events::
+
+ KVMI_EVENT_HYPERCALL
When an event is enabled, the introspection tool is notified and it
must reply with: continue, retry, crash, etc. (see **Events** below).
@@ -764,3 +767,34 @@ This event is sent in response to a *KVMI_VCPU_PAUSE* command.
This event has a low priority. It will be sent after any other vCPU
introspection event and when no vCPU introspection command is queued.
+
+3. KVMI_EVENT_HYPERCALL
+-----------------------
+
+:Architectures: x86
+:Versions: >= 1
+:Actions: CONTINUE, CRASH
+:Parameters:
+
+::
+
+ struct kvmi_event;
+
+:Returns:
+
+::
+
+ struct kvmi_vcpu_hdr;
+ struct kvmi_event_reply;
+
+This event is sent on a specific user hypercall when the introspection has
+been enabled for this event (see *KVMI_VCPU_CONTROL_EVENTS*).
+
+The hypercall number must be ``KVM_HC_XEN_HVM_OP`` with the
+``KVM_HC_XEN_HVM_OP_GUEST_REQUEST_VM_EVENT`` sub-function
+(see hypercalls.txt).
+
+It is used by the code residing inside the introspected guest to call the
+introspection tool and to report certain details about its operation. For
+example, a classic antimalware remediation tool can report what it has
+found during a scan.
diff --git a/arch/x86/include/uapi/asm/kvmi.h b/arch/x86/include/uapi/asm/kvmi.h
index 57c48ace417f..9882e68cab75 100644
--- a/arch/x86/include/uapi/asm/kvmi.h
+++ b/arch/x86/include/uapi/asm/kvmi.h
@@ -8,6 +8,8 @@
#include <asm/kvm.h>
+#define KVM_HC_XEN_HVM_OP_GUEST_REQUEST_VM_EVENT 24
+
struct kvmi_event_arch {
__u8 mode; /* 2, 4 or 8 */
__u8 padding[7];
diff --git a/arch/x86/kvm/kvmi.c b/arch/x86/kvm/kvmi.c
index bba85f333639..f597b3c1cba0 100644
--- a/arch/x86/kvm/kvmi.c
+++ b/arch/x86/kvm/kvmi.c
@@ -159,3 +159,36 @@ int kvmi_arch_cmd_vcpu_get_cpuid(struct kvm_vcpu *vcpu,
return 0;
}
+
+bool kvmi_arch_is_agent_hypercall(struct kvm_vcpu *vcpu)
+{
+ unsigned long subfunc1, subfunc2;
+ bool longmode = is_64_bit_mode(vcpu);
+
+ if (longmode) {
+ subfunc1 = kvm_rdi_read(vcpu);
+ subfunc2 = kvm_rsi_read(vcpu);
+ } else {
+ subfunc1 = kvm_rbx_read(vcpu);
+ subfunc1 &= 0xFFFFFFFF;
+ subfunc2 = kvm_rcx_read(vcpu);
+ subfunc2 &= 0xFFFFFFFF;
+ }
+
+ return (subfunc1 == KVM_HC_XEN_HVM_OP_GUEST_REQUEST_VM_EVENT
+ && subfunc2 == 0);
+}
+
+void kvmi_arch_hypercall_event(struct kvm_vcpu *vcpu)
+{
+ u32 action;
+
+ action = kvmi_msg_send_hypercall(vcpu);
+ switch (action) {
+ case KVMI_EVENT_ACTION_CONTINUE:
+ break;
+ default:
+ kvmi_handle_common_event_actions(vcpu->kvm, action,
+ "HYPERCALL");
+ }
+}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 46a135595893..b4a7805ce9e4 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7433,11 +7433,14 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
{
unsigned long nr, a0, a1, a2, a3, ret;
int op_64_bit;
+ bool kvmi_hc;
- if (kvm_hv_hypercall_enabled(vcpu->kvm))
+ nr = kvm_rax_read(vcpu);
+ kvmi_hc = (u32)nr == KVM_HC_XEN_HVM_OP;
+
+ if (kvm_hv_hypercall_enabled(vcpu->kvm) && !kvmi_hc)
return kvm_hv_hypercall(vcpu);
- nr = kvm_rax_read(vcpu);
a0 = kvm_rbx_read(vcpu);
a1 = kvm_rcx_read(vcpu);
a2 = kvm_rdx_read(vcpu);
@@ -7454,7 +7457,7 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
a3 &= 0xFFFFFFFF;
}
- if (kvm_x86_ops->get_cpl(vcpu) != 0) {
+ if (kvm_x86_ops->get_cpl(vcpu) != 0 && !kvmi_hc) {
ret = -KVM_EPERM;
goto out;
}
@@ -7480,6 +7483,13 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
kvm_sched_yield(vcpu->kvm, a0);
ret = 0;
break;
+#ifdef CONFIG_KVM_INTROSPECTION
+ case KVM_HC_XEN_HVM_OP:
+ ret = 0;
+ if (!kvmi_hypercall_event(vcpu))
+ ret = -KVM_ENOSYS;
+ break;
+#endif /* CONFIG_KVM_INTROSPECTION */
default:
ret = -KVM_ENOSYS;
break;
diff --git a/include/linux/kvmi_host.h b/include/linux/kvmi_host.h
index 68c76db83973..0a85bfbd0c0c 100644
--- a/include/linux/kvmi_host.h
+++ b/include/linux/kvmi_host.h
@@ -75,6 +75,7 @@ int kvmi_ioctl_event(struct kvm *kvm, void __user *argp);
int kvmi_ioctl_preunhook(struct kvm *kvm);
void kvmi_handle_requests(struct kvm_vcpu *vcpu);
+bool kvmi_hypercall_event(struct kvm_vcpu *vcpu);
#else
@@ -85,6 +86,7 @@ static inline void kvmi_destroy_vm(struct kvm *kvm) { }
static inline void kvmi_vcpu_uninit(struct kvm_vcpu *vcpu) { }
static inline void kvmi_handle_requests(struct kvm_vcpu *vcpu) { }
+static inline bool kvmi_hypercall_event(struct kvm_vcpu *vcpu) { return false; }
#endif /* CONFIG_KVM_INTROSPECTION */
diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h
index 3ce388249682..53cebbe22099 100644
--- a/include/uapi/linux/kvm_para.h
+++ b/include/uapi/linux/kvm_para.h
@@ -33,6 +33,7 @@
#define KVM_HC_CLOCK_PAIRING 9
#define KVM_HC_SEND_IPI 10
#define KVM_HC_SCHED_YIELD 11
+#define KVM_HC_XEN_HVM_OP 34 /* Xen's __HYPERVISOR_hvm_op */
/*
* hypercalls use architecture specific
diff --git a/include/uapi/linux/kvmi.h b/include/uapi/linux/kvmi.h
index 05535a7d9313..20e2f154ab88 100644
--- a/include/uapi/linux/kvmi.h
+++ b/include/uapi/linux/kvmi.h
@@ -39,6 +39,7 @@ enum {
enum {
KVMI_EVENT_UNHOOK = 0,
KVMI_EVENT_PAUSE_VCPU = 1,
+ KVMI_EVENT_HYPERCALL = 2,
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 fa23ca0ed0d7..ef4e33e92fff 100644
--- a/tools/testing/selftests/kvm/x86_64/kvmi_test.c
+++ b/tools/testing/selftests/kvm/x86_64/kvmi_test.c
@@ -48,6 +48,7 @@ struct vcpu_worker_data {
enum {
GUEST_TEST_NOOP = 0,
+ GUEST_TEST_HYPERCALL,
};
#define GUEST_REQUEST_TEST() GUEST_SYNC(0)
@@ -61,12 +62,23 @@ static int guest_test_id(void)
return READ_ONCE(test_id);
}
+static void guest_hypercall_test(void)
+{
+ asm volatile("mov $34, %rax");
+ asm volatile("mov $24, %rdi");
+ asm volatile("mov $0, %rsi");
+ asm volatile(".byte 0x0f,0x01,0xc1");
+}
+
static void guest_code(void)
{
while (true) {
switch (guest_test_id()) {
case GUEST_TEST_NOOP:
break;
+ case GUEST_TEST_HYPERCALL:
+ guest_hypercall_test();
+ break;
}
GUEST_SIGNAL_TEST_DONE();
}
@@ -942,6 +954,36 @@ static void test_cmd_vcpu_get_cpuid(struct kvm_vm *vm)
function, index, rpl.eax, rpl.ebx, rpl.ecx, rpl.edx);
}
+static void test_event_hypercall(struct kvm_vm *vm)
+{
+ struct vcpu_worker_data data = {
+ .vm = vm,
+ .vcpu_id = VCPU_ID,
+ .test_id = GUEST_TEST_HYPERCALL,
+ };
+ struct kvmi_msg_hdr hdr;
+ struct kvmi_event ev;
+ struct vcpu_reply rpl = {};
+ __u16 event_id = KVMI_EVENT_HYPERCALL;
+ pthread_t vcpu_thread;
+
+ enable_vcpu_event(vm, event_id);
+
+ vcpu_thread = start_vcpu_worker(&data);
+
+ receive_event(&hdr, &ev, sizeof(ev), event_id);
+
+ DEBUG("Hypercall event, rip 0x%llx\n",
+ ev.arch.regs.rip);
+
+ reply_to_event(&hdr, &ev, 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();
@@ -961,6 +1003,7 @@ static void test_introspection(struct kvm_vm *vm)
test_cmd_vcpu_get_registers(vm);
test_cmd_vcpu_set_registers(vm);
test_cmd_vcpu_get_cpuid(vm);
+ test_event_hypercall(vm);
unhook_introspection(vm);
}
diff --git a/virt/kvm/introspection/kvmi.c b/virt/kvm/introspection/kvmi.c
index 8ffbf46bc17d..a1c059489dea 100644
--- a/virt/kvm/introspection/kvmi.c
+++ b/virt/kvm/introspection/kvmi.c
@@ -828,3 +828,25 @@ void kvmi_post_reply(struct kvm_vcpu *vcpu)
vcpui->have_delayed_regs = false;
}
}
+
+bool kvmi_hypercall_event(struct kvm_vcpu *vcpu)
+{
+ struct kvm_introspection *kvmi;
+ bool ret = false;
+
+ if (!kvmi_arch_is_agent_hypercall(vcpu))
+ return ret;
+
+ kvmi = kvmi_get(vcpu->kvm);
+ if (!kvmi)
+ return ret;
+
+ if (is_event_enabled(vcpu, KVMI_EVENT_HYPERCALL)) {
+ kvmi_arch_hypercall_event(vcpu);
+ ret = true;
+ }
+
+ kvmi_put(vcpu->kvm);
+
+ return ret;
+}
diff --git a/virt/kvm/introspection/kvmi_int.h b/virt/kvm/introspection/kvmi_int.h
index 1b3d8958e6c8..3dbcf944a606 100644
--- a/virt/kvm/introspection/kvmi_int.h
+++ b/virt/kvm/introspection/kvmi_int.h
@@ -22,7 +22,8 @@
BIT(KVMI_EVENT_UNHOOK) \
)
#define KVMI_KNOWN_VCPU_EVENTS ( \
- BIT(KVMI_EVENT_PAUSE_VCPU) \
+ BIT(KVMI_EVENT_HYPERCALL) \
+ | BIT(KVMI_EVENT_PAUSE_VCPU) \
)
#define KVMI_KNOWN_EVENTS (KVMI_KNOWN_VM_EVENTS | KVMI_KNOWN_VCPU_EVENTS)
@@ -52,6 +53,11 @@ static inline bool is_vm_event_enabled(struct kvm_introspection *kvmi,
return test_bit(event, kvmi->vm_event_enable_mask);
}
+static inline bool is_event_enabled(struct kvm_vcpu *vcpu, int event)
+{
+ return test_bit(event, VCPUI(vcpu)->ev_mask);
+}
+
/* kvmi_msg.c */
bool kvmi_sock_get(struct kvm_introspection *kvmi, int fd);
void kvmi_sock_shutdown(struct kvm_introspection *kvmi);
@@ -59,6 +65,7 @@ void kvmi_sock_put(struct kvm_introspection *kvmi);
bool kvmi_msg_process(struct kvm_introspection *kvmi);
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);
/* kvmi.c */
void *kvmi_msg_alloc(void);
@@ -69,6 +76,8 @@ int kvmi_add_job(struct kvm_vcpu *vcpu,
void *ctx, void (*free_fct)(void *ctx));
void kvmi_run_jobs(struct kvm_vcpu *vcpu);
void kvmi_post_reply(struct kvm_vcpu *vcpu);
+void kvmi_handle_common_event_actions(struct kvm *kvm,
+ u32 action, const char *str);
int kvmi_cmd_vm_control_events(struct kvm_introspection *kvmi,
unsigned int event_id, bool enable);
int kvmi_cmd_vcpu_control_events(struct kvm_vcpu *vcpu,
@@ -96,5 +105,7 @@ int kvmi_arch_cmd_vcpu_get_registers(struct kvm_vcpu *vcpu,
int kvmi_arch_cmd_vcpu_get_cpuid(struct kvm_vcpu *vcpu,
const struct kvmi_vcpu_get_cpuid *req,
struct kvmi_vcpu_get_cpuid_reply *rpl);
+bool kvmi_arch_is_agent_hypercall(struct kvm_vcpu *vcpu);
+void kvmi_arch_hypercall_event(struct kvm_vcpu *vcpu);
#endif
diff --git a/virt/kvm/introspection/kvmi_msg.c b/virt/kvm/introspection/kvmi_msg.c
index 11873cb3c23b..bcdf104eaa43 100644
--- a/virt/kvm/introspection/kvmi_msg.c
+++ b/virt/kvm/introspection/kvmi_msg.c
@@ -868,3 +868,15 @@ u32 kvmi_msg_send_vcpu_pause(struct kvm_vcpu *vcpu)
return action;
}
+
+u32 kvmi_msg_send_hypercall(struct kvm_vcpu *vcpu)
+{
+ int err, action;
+
+ err = kvmi_send_event(vcpu, KVMI_EVENT_HYPERCALL, NULL, 0,
+ NULL, 0, &action);
+ if (err)
+ return KVMI_EVENT_ACTION_CONTINUE;
+
+ return action;
+}
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