[PATCH v2 18/26] KVM: x86 emulator: implement ENTER

Avi Kivity
2012-06-27T15:20:15Z

Opcode C8.

Only ENTER with lexical nesting depth 0 is implemented, since others are
very rare. We'll fail emulation if nonzero lexical depth is used so data
is not corrupted.

Signed-off-by: Avi Kivity <avi@redhat.com>
---
arch/x86/kvm/emulate.c | 28 +++++++++++++++++++++++++++-
1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index acc647d..b4b326e 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -454,6 +454,11 @@ static ulong stack_mask(struct x86_emulate_ctxt *ctxt)
return ~0U >> ((ss.d ^ 1) * 16); /* d=0: 0xffff; d=1: 0xffffffff */
}

+static int stack_size(struct x86_emulate_ctxt *ctxt)
+{
+ return (__fls(stack_mask(ctxt)) + 1) >> 3;
+}
+
/* Access/update address held in a register, based on addressing mode. */
static inline unsigned long
address_mask(struct x86_emulate_ctxt *ctxt, unsigned long reg)
@@ -1592,6 +1597,26 @@ static int em_popf(struct x86_emulate_ctxt *ctxt)
return emulate_popf(ctxt, &ctxt->dst.val, ctxt->op_bytes);
}

+static int em_enter(struct x86_emulate_ctxt *ctxt)
+{
+ int rc;
+ unsigned frame_size = ctxt->src.val;
+ unsigned nesting_level = ctxt->src2.val & 31;
+
+ if (nesting_level)
+ return X86EMUL_UNHANDLEABLE;
+
+ rc = push(ctxt, &ctxt->regs[VCPU_REGS_RBP], stack_size(ctxt));
+ if (rc != X86EMUL_CONTINUE)
+ return rc;
+ assign_masked(&ctxt->regs[VCPU_REGS_RBP], ctxt->regs[VCPU_REGS_RSP],
+ stack_mask(ctxt));
+ assign_masked(&ctxt->regs[VCPU_REGS_RSP],
+ ctxt->regs[VCPU_REGS_RSP] - frame_size,
+ stack_mask(ctxt));
+ return X86EMUL_CONTINUE;
+}
+
static int em_leave(struct x86_emulate_ctxt *ctxt)
{
assign_masked(&ctxt->regs[VCPU_REGS_RSP], ctxt->regs[VCPU_REGS_RBP],
@@ -3657,7 +3682,8 @@ static int check_perm_out(struct x86_emulate_ctxt *ctxt)
I(DstReg | SrcMemFAddr | ModRM | No64 | Src2DS, em_lseg),
G(ByteOp, group11), G(0, group11),
/* 0xC8 - 0xCF */
- N, I(Stack, em_leave), N, I(ImplicitOps | Stack, em_ret_far),
+ I(Stack | SrcImmU16 | Src2ImmByte, em_enter), I(Stack, em_leave),
+ N, I(ImplicitOps | Stack, em_ret_far),
D(ImplicitOps), DI(SrcImmByte, intn),
D(ImplicitOps | No64), II(ImplicitOps, em_iret, iret),
/* 0xD0 - 0xD7 */
--
1.7.11