From: Mihai Donțu <mdo...@bitdefender.com>
This event is sent when a breakpoint was reached.
The introspection tool can place breakpoints and use them as notification
for when the OS or an application has reached a certain state or is
trying to perform a certain operation (eg. create a process).
Signed-off-by: Mihai Donțu <mdo...@bitdefender.com>
Co-developed-by: Nicușor Cîțu <nicu.c...@icloud.com>
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 | 48 ++++++++++++++++++
arch/x86/kvm/kvmi.c | 50 +++++++++++++++++++
arch/x86/kvm/svm/svm.c | 34 +++++++++++++
arch/x86/kvm/vmx/vmx.c | 17 +++++--
include/linux/kvmi_host.h | 3 ++
include/uapi/linux/kvmi.h | 11 +++-
.../testing/selftests/kvm/x86_64/kvmi_test.c | 46 +++++++++++++++++
virt/kvm/introspection/kvmi.c | 25 ++++++++++
virt/kvm/introspection/kvmi_int.h | 4 ++
virt/kvm/introspection/kvmi_msg.c | 18 +++++++
10 files changed, 250 insertions(+), 6 deletions(-)
diff --git a/Documentation/virt/kvm/kvmi.rst b/Documentation/virt/kvm/kvmi.rst
index 023c885638af..c89f383e48f9 100644
--- a/Documentation/virt/kvm/kvmi.rst
+++ b/Documentation/virt/kvm/kvmi.rst
@@ -538,6 +538,7 @@ command) before returning to guest.
Enables/disables vCPU introspection events. This command can be used with
the following events::
+ KVMI_VCPU_EVENT_BREAKPOINT
KVMI_VCPU_EVENT_HYPERCALL
When an event is enabled, the introspection tool is notified and
@@ -559,6 +560,9 @@ 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_EBUSY - the event can't be intercepted right now
+ (e.g. KVMI_VCPU_EVENT_BREAKPOINT if the #BP event
+ is already intercepted by userspace)
11. KVMI_VCPU_GET_REGISTERS
---------------------------
@@ -817,3 +821,47 @@ found during a scan.
The most useful registers describing the vCPU state can be read from
``kvmi_vcpu_event.arch.regs``.
+
+4. KVMI_VCPU_EVENT_BREAKPOINT
+-----------------------------
+
+:Architectures: x86
+:Versions: >= 1
+:Actions: CONTINUE, CRASH, RETRY
+:Parameters:
+
+::
+
+ struct kvmi_event_hdr;
+ struct kvmi_vcpu_event;
+ struct kvmi_vcpu_event_breakpoint {
+ __u64 gpa;
+ __u8 insn_len;
+ __u8 padding[7];
+ };
+
+:Returns:
+
+::
+
+ struct kvmi_vcpu_hdr;
+ struct kvmi_vcpu_event_reply;
+
+This event is sent when a breakpoint was reached and the introspection has
+been enabled for this event (see *KVMI_VCPU_CONTROL_EVENTS*).
+
+Some of these breakpoints could have been injected by the introspection tool,
+placed in the slack space of various functions and used as notification
+for when the OS or an application has reached a certain state or is
+trying to perform a certain operation (like creating a process).
+
+``kvmi_vcpu_event`` (with the vCPU state), the guest physical address
+(``gpa``) where the breakpoint instruction is placed and the breakpoint
+instruction length (``insn_len``) are sent to the introspection tool.
+
+The *RETRY* action is used by the introspection tool for its own
+breakpoints. In most cases, the tool will change the instruction pointer
+before returning this action.
+
+The *CONTINUE* action will cause the breakpoint exception to be reinjected
+(the OS will handle it).
diff --git a/arch/x86/kvm/kvmi.c b/arch/x86/kvm/kvmi.c
index 5f08cf0d19bc..0bb6f38f1213 100644
--- a/arch/x86/kvm/kvmi.c
+++ b/arch/x86/kvm/kvmi.c
@@ -11,6 +11,7 @@
void kvmi_arch_init_vcpu_events_mask(unsigned long *supported)
{
+ set_bit(KVMI_VCPU_EVENT_BREAKPOINT, supported);
set_bit(KVMI_VCPU_EVENT_HYPERCALL, supported);
}
@@ -160,3 +161,52 @@ bool kvmi_arch_is_agent_hypercall(struct kvm_vcpu *vcpu)
return (subfunc1 == KVM_HC_XEN_HVM_OP_GUEST_REQUEST_VM_EVENT
&& subfunc2 == 0);
}
+
+static int kvmi_control_bp_intercept(struct kvm_vcpu *vcpu, bool enable)
+{
+ struct kvm_guest_debug dbg = {};
+ int err = 0;
+
+ if (enable)
+ dbg.control = KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP;
+
+ err = kvm_arch_vcpu_set_guest_debug(vcpu, &dbg);
+
+ return err;
+}
+
+int kvmi_arch_cmd_control_intercept(struct kvm_vcpu *vcpu,
+ unsigned int event_id, bool enable)
+{
+ int err = 0;
+
+ switch (event_id) {
+ case KVMI_VCPU_EVENT_BREAKPOINT:
+ err = kvmi_control_bp_intercept(vcpu, enable);
+ break;
+ default:
+ break;
+ }
+
+ return err;
+}
+
+void kvmi_arch_breakpoint_event(struct kvm_vcpu *vcpu, u64 gva, u8 insn_len)
+{
+ u32 action;
+ u64 gpa;
+
+ gpa = kvm_mmu_gva_to_gpa_system(vcpu, gva, 0, NULL);
+
+ action = kvmi_msg_send_vcpu_bp(vcpu, gpa, insn_len);
+ switch (action) {
+ case KVMI_EVENT_ACTION_CONTINUE:
+ kvm_queue_exception(vcpu, BP_VECTOR);
+ break;
+ case KVMI_EVENT_ACTION_RETRY:
+ /* rip was most likely adjusted past the INT 3 instruction */
+ break;
+ default:
+ kvmi_handle_common_event_actions(vcpu, action);
+ }
+}
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index c6730ec39c58..baca455212f9 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -25,6 +25,7 @@
#include <linux/pagemap.h>
#include <linux/swap.h>
#include <linux/rwsem.h>
+#include <linux/kvmi_host.h>
#include <asm/apic.h>
#include <asm/perf_event.h>
@@ -1958,10 +1959,43 @@ static int db_interception(struct vcpu_svm *svm)
return 1;
}
+static unsigned svm_get_instruction_len(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_svm *svm = to_svm(vcpu);
+ unsigned long rip = kvm_rip_read(vcpu);
+ unsigned long next_rip = 0;
+ unsigned insn_len;
+
+ if (static_cpu_has(X86_FEATURE_NRIPS))
+ next_rip = svm->vmcb->control.next_rip;
+
+ if (!next_rip) {
+ if (!kvm_emulate_instruction(vcpu, EMULTYPE_SKIP))
+ return 0;
+
+ next_rip = kvm_rip_read(vcpu);
+ kvm_rip_write(vcpu, rip);
+ }
+
+ insn_len = next_rip - rip;
+ if (insn_len > MAX_INST_SIZE) {
+ pr_err("%s: ip 0x%lx next 0x%lx\n",
+ __func__, rip, next_rip);
+ return 0;
+ }
+
+ return insn_len;
+}
+
static int bp_interception(struct vcpu_svm *svm)
{
struct kvm_run *kvm_run = svm->vcpu.run;
+ if (!kvmi_breakpoint_event(&svm->vcpu, svm->vmcb->save.cs.base +
+ svm->vmcb->save.rip,
+ svm_get_instruction_len(&svm->vcpu)))
+ return 1;
+
kvm_run->exit_reason = KVM_EXIT_DEBUG;
kvm_run->debug.arch.pc = svm->vmcb->save.cs.base + svm->vmcb->save.rip;
kvm_run->debug.arch.exception = BP_VECTOR;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 1c8fbd6209ce..9bfa2e9f8161 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -28,6 +28,7 @@
#include <linux/tboot.h>
#include <linux/trace_events.h>
#include <linux/entry-kvm.h>
+#include <linux/kvmi_host.h>
#include <asm/apic.h>
#include <asm/asm.h>
@@ -4814,7 +4815,7 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
struct vcpu_vmx *vmx = to_vmx(vcpu);
struct kvm_run *kvm_run = vcpu->run;
u32 intr_info, ex_no, error_code;
- unsigned long cr2, rip, dr6;
+ unsigned long cr2, dr6;
u32 vect_info;
vect_info = vmx->idt_vectoring_info;
@@ -4895,7 +4896,10 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
kvm_run->debug.arch.dr6 = dr6 | DR6_FIXED_1 | DR6_RTM;
kvm_run->debug.arch.dr7 = vmcs_readl(GUEST_DR7);
fallthrough;
- case BP_VECTOR:
+ case BP_VECTOR: {
+ unsigned long gva = vmcs_readl(GUEST_CS_BASE) +
+ kvm_rip_read(vcpu);
+
/*
* Update instruction length as we may reinject #BP from
* user space while in guest debugging mode. Reading it for
@@ -4903,11 +4907,16 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
*/
vmx->vcpu.arch.event_exit_inst_len =
vmcs_read32(VM_EXIT_INSTRUCTION_LEN);
+
+ if (!kvmi_breakpoint_event(vcpu, gva,
+ vmx->vcpu.arch.event_exit_inst_len))
+ return 1;
+
kvm_run->exit_reason = KVM_EXIT_DEBUG;
- rip = kvm_rip_read(vcpu);
- kvm_run->debug.arch.pc = vmcs_readl(GUEST_CS_BASE) + rip;
+ kvm_run->debug.arch.pc = gva;
kvm_run->debug.arch.exception = ex_no;
break;
+ }
case AC_VECTOR:
if (guest_inject_ac(vcpu)) {
kvm_queue_exception_e(vcpu, AC_VECTOR, error_code);
diff --git a/include/linux/kvmi_host.h b/include/linux/kvmi_host.h
index 1fb775b0de33..30b7269468dd 100644
--- a/include/linux/kvmi_host.h
+++ b/include/linux/kvmi_host.h
@@ -70,6 +70,7 @@ int kvmi_ioctl_preunhook(struct kvm *kvm);
void kvmi_handle_requests(struct kvm_vcpu *vcpu);
bool kvmi_hypercall_event(struct kvm_vcpu *vcpu);
+bool kvmi_breakpoint_event(struct kvm_vcpu *vcpu, u64 gva, u8 insn_len);
#else
@@ -82,6 +83,8 @@ 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;
}
+static inline bool kvmi_breakpoint_event(struct kvm_vcpu *vcpu, u64 gva,
+ u8 insn_len) { return true; }
#endif /* CONFIG_KVM_INTROSPECTION */
diff --git a/include/uapi/linux/kvmi.h b/include/uapi/linux/kvmi.h
index 3dfc3486cc46..ea66f3f803e7 100644
--- a/include/uapi/linux/kvmi.h
+++ b/include/uapi/linux/kvmi.h
@@ -54,8 +54,9 @@ enum {
};
enum {
- KVMI_VCPU_EVENT_PAUSE = KVMI_VCPU_EVENT_ID(0),
- KVMI_VCPU_EVENT_HYPERCALL = KVMI_VCPU_EVENT_ID(1),
+ KVMI_VCPU_EVENT_PAUSE = KVMI_VCPU_EVENT_ID(0),
+ KVMI_VCPU_EVENT_HYPERCALL = KVMI_VCPU_EVENT_ID(1),
+ KVMI_VCPU_EVENT_BREAKPOINT = KVMI_VCPU_EVENT_ID(2),
KVMI_NEXT_VCPU_EVENT
};
@@ -160,4 +161,10 @@ struct kvmi_vcpu_control_events {
__u32 padding2;
};
+struct kvmi_vcpu_event_breakpoint {
+ __u64 gpa;
+ __u8 insn_len;
+ __u8 padding[7];
+};
+
#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 8c772b2bff2a..ccb9a3a997d8 100644
--- a/tools/testing/selftests/kvm/x86_64/kvmi_test.c
+++ b/tools/testing/selftests/kvm/x86_64/kvmi_test.c
@@ -53,6 +53,7 @@ struct vcpu_worker_data {
enum {
GUEST_TEST_NOOP = 0,
+ GUEST_TEST_BP,
GUEST_TEST_HYPERCALL,
};
@@ -68,6 +69,11 @@ static int guest_test_id(void)
return READ_ONCE(test_id);
}
+static void guest_bp_test(void)
+{
+ asm volatile("int3");
+}
+
static void guest_hypercall_test(void)
{
asm volatile("mov $34, %rax");
@@ -82,6 +88,9 @@ static void guest_code(void)
switch (guest_test_id()) {
case GUEST_TEST_NOOP:
break;
+ case GUEST_TEST_BP:
+ guest_bp_test();
+ break;
case GUEST_TEST_HYPERCALL:
guest_hypercall_test();
break;
@@ -1018,6 +1027,42 @@ static void test_event_hypercall(struct kvm_vm *vm)
disable_vcpu_event(vm, event_id);
}
+static void test_event_breakpoint(struct kvm_vm *vm)
+{
+ struct vcpu_worker_data data = {
+ .vm = vm,
+ .vcpu_id = VCPU_ID,
+ .test_id = GUEST_TEST_BP,
+ };
+ struct kvmi_msg_hdr hdr;
+ struct {
+ struct vcpu_event vcpu_ev;
+ struct kvmi_vcpu_event_breakpoint bp;
+ } ev;
+ struct vcpu_reply rpl = {};
+ __u16 event_id = KVMI_VCPU_EVENT_BREAKPOINT;
+ pthread_t vcpu_thread;
+
+ enable_vcpu_event(vm, event_id);
+
+ vcpu_thread = start_vcpu_worker(&data);
+
+ receive_vcpu_event(&hdr, &ev.vcpu_ev, sizeof(ev), event_id);
+
+ pr_debug("Breakpoint event, rip 0x%llx, len %u\n",
+ ev.vcpu_ev.common.arch.regs.rip, ev.bp.insn_len);
+
+ ev.vcpu_ev.common.arch.regs.rip += ev.bp.insn_len;
+ __set_registers(vm, &ev.vcpu_ev.common.arch.regs);
+
+ reply_to_event(&hdr, &ev.vcpu_ev, KVMI_EVENT_ACTION_RETRY,
+ &rpl, sizeof(rpl));
+
+ wait_vcpu_worker(vcpu_thread);
+
+ disable_vcpu_event(vm, event_id);
+}
+
static void test_introspection(struct kvm_vm *vm)
{
srandom(time(0));
@@ -1039,6 +1084,7 @@ static void test_introspection(struct kvm_vm *vm)
test_cmd_vcpu_set_registers(vm);
test_cmd_vcpu_get_cpuid(vm);
test_event_hypercall(vm);
+ test_event_breakpoint(vm);
unhook_introspection(vm);
}
diff --git a/virt/kvm/introspection/kvmi.c b/virt/kvm/introspection/kvmi.c
index 7a4b9b5c3248..bd1e6afaed9f 100644
--- a/virt/kvm/introspection/kvmi.c
+++ b/virt/kvm/introspection/kvmi.c
@@ -639,6 +639,11 @@ int kvmi_cmd_vcpu_control_events(struct kvm_vcpu *vcpu,
u16 event_id, bool enable)
{
struct kvm_vcpu_introspection *vcpui = VCPUI(vcpu);
+ int err;
+
+ err = kvmi_arch_cmd_control_intercept(vcpu, event_id, enable);
+ if (err)
+ return err;
if (enable)
set_bit(event_id, vcpui->ev_enable_mask);
@@ -875,3 +880,23 @@ bool kvmi_hypercall_event(struct kvm_vcpu *vcpu)
return ret;
}
+
+bool kvmi_breakpoint_event(struct kvm_vcpu *vcpu, u64 gva, u8 insn_len)
+{
+ struct kvm_introspection *kvmi;
+ bool ret = true;
+
+ kvmi = kvmi_get(vcpu->kvm);
+ if (!kvmi)
+ return ret;
+
+ if (is_vcpu_event_enabled(vcpu, KVMI_VCPU_EVENT_BREAKPOINT)) {
+ kvmi_arch_breakpoint_event(vcpu, gva, insn_len);
+ ret = false;
+ }
+
+ kvmi_put(vcpu->kvm);
+
+ return ret;
+}
+EXPORT_SYMBOL(kvmi_breakpoint_event);
diff --git a/virt/kvm/introspection/kvmi_int.h
b/virt/kvm/introspection/kvmi_int.h
index 72f0b75d2cf5..ff745e3cebaf 100644
--- a/virt/kvm/introspection/kvmi_int.h
+++ b/virt/kvm/introspection/kvmi_int.h
@@ -45,6 +45,7 @@ int kvmi_msg_vcpu_reply(const struct kvmi_vcpu_msg_job *job,
const void *rpl, size_t rpl_size);
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);
/* kvmi.c */
void *kvmi_msg_alloc(void);
@@ -79,5 +80,8 @@ void kvmi_arch_setup_vcpu_event(struct kvm_vcpu *vcpu,
struct kvmi_vcpu_event *ev);
void kvmi_arch_post_reply(struct kvm_vcpu *vcpu);
bool kvmi_arch_is_agent_hypercall(struct kvm_vcpu *vcpu);
+void kvmi_arch_breakpoint_event(struct kvm_vcpu *vcpu, u64 gva, u8 insn_len);
+int kvmi_arch_cmd_control_intercept(struct kvm_vcpu *vcpu,
+ unsigned int event_id, bool enable);
#endif
diff --git a/virt/kvm/introspection/kvmi_msg.c
b/virt/kvm/introspection/kvmi_msg.c
index a515734dc937..ee41f2397822 100644
--- a/virt/kvm/introspection/kvmi_msg.c
+++ b/virt/kvm/introspection/kvmi_msg.c
@@ -757,3 +757,21 @@ u32 kvmi_msg_send_vcpu_hypercall(struct kvm_vcpu *vcpu)
return action;
}
+
+u32 kvmi_msg_send_vcpu_bp(struct kvm_vcpu *vcpu, u64 gpa, u8 insn_len)
+{
+ struct kvmi_vcpu_event_breakpoint e;
+ u32 action;
+ int err;
+
+ memset(&e, 0, sizeof(e));
+ e.gpa = gpa;
+ e.insn_len = insn_len;
+
+ err = kvmi_send_vcpu_event(vcpu, KVMI_VCPU_EVENT_BREAKPOINT,
+ &e, sizeof(e), NULL, 0, &action);
+ if (err)
+ return KVMI_EVENT_ACTION_CONTINUE;
+
+ return action;
+}
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