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KVM: x86 emulator: Add sysexit emulation

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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@amd.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Andre Przywara <andre.przywara@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Andre Przywara 2009-06-18 12:56:02 +02:00 committed by Avi Kivity
parent 8c60435261
commit 4668f05078
1 changed files with 71 additions and 1 deletions
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72
arch/x86/kvm/x86_emulate.c
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@ -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;