From: Andre Przywara <andre.przywara@xxxxxxx>
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: Christoph Egger <christoph.egger@xxxxxxx>
Signed-off-by: Amit Shah <amit.shah@xxxxxxxxxx>
Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
---
arch/x86/kvm/x86_emulate.c | 72 +++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 71 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kvm/x86_emulate.c b/arch/x86/kvm/x86_emulate.c
index 7a9bddb..c6663d4 100644
--- a/arch/x86/kvm/x86_emulate.c
+++ b/arch/x86/kvm/x86_emulate.c
@@ -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 */
- goto cannot_emulate;
+ 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;
--
1.6.3.3
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