KVM: VMX: Add Guest State Validity Checks
This patch adds functions to check whether guest state is VMX compliant.
Signed-off-by: Mohammed Gamal <m.gamal005@gmail.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 81db7d4..e889b76 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1721,6 +1721,186 @@
vmcs_writel(GUEST_GDTR_BASE, dt->base);
}
+static bool rmode_segment_valid(struct kvm_vcpu *vcpu, int seg)
+{
+ struct kvm_segment var;
+ u32 ar;
+
+ vmx_get_segment(vcpu, &var, seg);
+ ar = vmx_segment_access_rights(&var);
+
+ if (var.base != (var.selector << 4))
+ return false;
+ if (var.limit != 0xffff)
+ return false;
+ if (ar != 0xf3)
+ return false;
+
+ return true;
+}
+
+static bool code_segment_valid(struct kvm_vcpu *vcpu)
+{
+ struct kvm_segment cs;
+ unsigned int cs_rpl;
+
+ vmx_get_segment(vcpu, &cs, VCPU_SREG_CS);
+ cs_rpl = cs.selector & SELECTOR_RPL_MASK;
+
+ if (~cs.type & (AR_TYPE_CODE_MASK|AR_TYPE_ACCESSES_MASK))
+ return false;
+ if (!cs.s)
+ return false;
+ if (!(~cs.type & (AR_TYPE_CODE_MASK|AR_TYPE_WRITEABLE_MASK))) {
+ if (cs.dpl > cs_rpl)
+ return false;
+ } else if (cs.type & AR_TYPE_CODE_MASK) {
+ if (cs.dpl != cs_rpl)
+ return false;
+ }
+ if (!cs.present)
+ return false;
+
+ /* TODO: Add Reserved field check, this'll require a new member in the kvm_segment_field structure */
+ return true;
+}
+
+static bool stack_segment_valid(struct kvm_vcpu *vcpu)
+{
+ struct kvm_segment ss;
+ unsigned int ss_rpl;
+
+ vmx_get_segment(vcpu, &ss, VCPU_SREG_SS);
+ ss_rpl = ss.selector & SELECTOR_RPL_MASK;
+
+ if ((ss.type != 3) || (ss.type != 7))
+ return false;
+ if (!ss.s)
+ return false;
+ if (ss.dpl != ss_rpl) /* DPL != RPL */
+ return false;
+ if (!ss.present)
+ return false;
+
+ return true;
+}
+
+static bool data_segment_valid(struct kvm_vcpu *vcpu, int seg)
+{
+ struct kvm_segment var;
+ unsigned int rpl;
+
+ vmx_get_segment(vcpu, &var, seg);
+ rpl = var.selector & SELECTOR_RPL_MASK;
+
+ if (!var.s)
+ return false;
+ if (!var.present)
+ return false;
+ if (~var.type & (AR_TYPE_CODE_MASK|AR_TYPE_WRITEABLE_MASK)) {
+ if (var.dpl < rpl) /* DPL < RPL */
+ return false;
+ }
+
+ /* TODO: Add other members to kvm_segment_field to allow checking for other access
+ * rights flags
+ */
+ return true;
+}
+
+static bool tr_valid(struct kvm_vcpu *vcpu)
+{
+ struct kvm_segment tr;
+
+ vmx_get_segment(vcpu, &tr, VCPU_SREG_TR);
+
+ if (tr.selector & SELECTOR_TI_MASK) /* TI = 1 */
+ return false;
+ if ((tr.type != 3) || (tr.type != 11)) /* TODO: Check if guest is in IA32e mode */
+ return false;
+ if (!tr.present)
+ return false;
+
+ return true;
+}
+
+static bool ldtr_valid(struct kvm_vcpu *vcpu)
+{
+ struct kvm_segment ldtr;
+
+ vmx_get_segment(vcpu, &ldtr, VCPU_SREG_LDTR);
+
+ if (ldtr.selector & SELECTOR_TI_MASK) /* TI = 1 */
+ return false;
+ if (ldtr.type != 2)
+ return false;
+ if (!ldtr.present)
+ return false;
+
+ return true;
+}
+
+static bool cs_ss_rpl_check(struct kvm_vcpu *vcpu)
+{
+ struct kvm_segment cs, ss;
+
+ vmx_get_segment(vcpu, &cs, VCPU_SREG_CS);
+ vmx_get_segment(vcpu, &ss, VCPU_SREG_SS);
+
+ return ((cs.selector & SELECTOR_RPL_MASK) ==
+ (ss.selector & SELECTOR_RPL_MASK));
+}
+
+/*
+ * Check if guest state is valid. Returns true if valid, false if
+ * not.
+ * We assume that registers are always usable
+ */
+static bool guest_state_valid(struct kvm_vcpu *vcpu)
+{
+ /* real mode guest state checks */
+ if (!(vcpu->arch.cr0 & X86_CR0_PE)) {
+ if (!rmode_segment_valid(vcpu, VCPU_SREG_CS))
+ return false;
+ if (!rmode_segment_valid(vcpu, VCPU_SREG_SS))
+ return false;
+ if (!rmode_segment_valid(vcpu, VCPU_SREG_DS))
+ return false;
+ if (!rmode_segment_valid(vcpu, VCPU_SREG_ES))
+ return false;
+ if (!rmode_segment_valid(vcpu, VCPU_SREG_FS))
+ return false;
+ if (!rmode_segment_valid(vcpu, VCPU_SREG_GS))
+ return false;
+ } else {
+ /* protected mode guest state checks */
+ if (!cs_ss_rpl_check(vcpu))
+ return false;
+ if (!code_segment_valid(vcpu))
+ return false;
+ if (!stack_segment_valid(vcpu))
+ return false;
+ if (!data_segment_valid(vcpu, VCPU_SREG_DS))
+ return false;
+ if (!data_segment_valid(vcpu, VCPU_SREG_ES))
+ return false;
+ if (!data_segment_valid(vcpu, VCPU_SREG_FS))
+ return false;
+ if (!data_segment_valid(vcpu, VCPU_SREG_GS))
+ return false;
+ if (!tr_valid(vcpu))
+ return false;
+ if (!ldtr_valid(vcpu))
+ return false;
+ }
+ /* TODO:
+ * - Add checks on RIP
+ * - Add checks on RFLAGS
+ */
+
+ return true;
+}
+
static int init_rmode_tss(struct kvm *kvm)
{
gfn_t fn = rmode_tss_base(kvm) >> PAGE_SHIFT;