Commit 4668f050 authored by Andre Przywara's avatar Andre Przywara Committed by Avi Kivity
Browse files

KVM: x86 emulator: Add sysexit emulation 



Handle #UD intercept of the sysexit instruction in 64bit mode returning to
32bit compat mode on an AMD host.
Setup the segment descriptors for CS and SS and the EIP/ESP registers
according to the manual.

Signed-off-by: default avatarChristoph Egger <christoph.egger@amd.com>
Signed-off-by: default avatarAmit Shah <amit.shah@redhat.com>
Signed-off-by: default avatarAndre Przywara <andre.przywara@amd.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 8c604352

arch/x86/kvm/x86_emulate.c

+71 −1
Original line number Diff line number Diff line
@@ -1541,6 +1541,73 @@ emulate_sysenter(struct x86_emulate_ctxt *ctxt) 
	return 0;

}



static int

emulate_sysexit(struct x86_emulate_ctxt *ctxt)

{

	struct decode_cache *c = &ctxt->decode;

	struct kvm_segment cs, ss;

	u64 msr_data;

	int usermode;



	/* inject #UD if LOCK prefix is used */

	if (c->lock_prefix)

		return -1;



	/* inject #GP if in real mode or paging is disabled */

	if (ctxt->mode == X86EMUL_MODE_REAL

		|| !(ctxt->vcpu->arch.cr0 & X86_CR0_PE)) {

		kvm_inject_gp(ctxt->vcpu, 0);

		return -1;

	}



	/* sysexit must be called from CPL 0 */

	if (kvm_x86_ops->get_cpl(ctxt->vcpu) != 0) {

		kvm_inject_gp(ctxt->vcpu, 0);

		return -1;

	}



	setup_syscalls_segments(ctxt, &cs, &ss);



	if ((c->rex_prefix & 0x8) != 0x0)

		usermode = X86EMUL_MODE_PROT64;

	else

		usermode = X86EMUL_MODE_PROT32;



	cs.dpl = 3;

	ss.dpl = 3;

	kvm_x86_ops->get_msr(ctxt->vcpu, MSR_IA32_SYSENTER_CS, &msr_data);

	switch (usermode) {

	case X86EMUL_MODE_PROT32:

		cs.selector = (u16)(msr_data + 16);

		if ((msr_data & 0xfffc) == 0x0) {

			kvm_inject_gp(ctxt->vcpu, 0);

			return -1;

		}

		ss.selector = (u16)(msr_data + 24);

		break;

	case X86EMUL_MODE_PROT64:

		cs.selector = (u16)(msr_data + 32);

		if (msr_data == 0x0) {

			kvm_inject_gp(ctxt->vcpu, 0);

			return -1;

		}

		ss.selector = cs.selector + 8;

		cs.db = 0;

		cs.l = 1;

		break;

	}

	cs.selector |= SELECTOR_RPL_MASK;

	ss.selector |= SELECTOR_RPL_MASK;



	kvm_x86_ops->set_segment(ctxt->vcpu, &cs, VCPU_SREG_CS);

	kvm_x86_ops->set_segment(ctxt->vcpu, &ss, VCPU_SREG_SS);



	c->eip = ctxt->vcpu->arch.regs[VCPU_REGS_RDX];

	c->regs[VCPU_REGS_RSP] = ctxt->vcpu->arch.regs[VCPU_REGS_RCX];



	return 0;

}



int

x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)

{
@@ -2215,7 +2282,10 @@ twobyte_insn: 
			goto writeback;

		break;

	case 0x35:		/* sysexit */

		if (emulate_sysexit(ctxt) == -1)

			goto cannot_emulate;

		else

			goto writeback;

		break;

	case 0x40 ... 0x4f:	/* cmov */

		c->dst.val = c->dst.orig_val = c->src.val;

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