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Commit 648dfaa7 authored by Mohammed Gamal's avatar Mohammed Gamal Committed by Avi Kivity
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KVM: VMX: Add Guest State Validity Checks 



This patch adds functions to check whether guest state is VMX compliant.

Signed-off-by: default avatarMohammed Gamal <m.gamal005@gmail.com>
Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
parent 6762b729

arch/x86/kvm/vmx.c

+180 −0
Original line number Diff line number Diff line
@@ -1721,6 +1721,186 @@ static void vmx_set_gdt(struct kvm_vcpu *vcpu, struct descriptor_table *dt) 
	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;