KVM: x86: decode_modrm does not regard modrm correctly
In one occassion, decode_modrm uses the rm field after it is extended with
REX.B to determine the addressing mode. Doing so causes it not to read the
offset for rip-relative addressing with REX.B=1.
This patch moves the fetch where we already mask REX.B away instead.
Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index cd2029b..a4703eb 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1223,6 +1223,7 @@
if (index_reg != 4)
modrm_ea += reg_read(ctxt, index_reg) << scale;
} else if ((ctxt->modrm_rm & 7) == 5 && ctxt->modrm_mod == 0) {
+ modrm_ea += insn_fetch(s32, ctxt);
if (ctxt->mode == X86EMUL_MODE_PROT64)
ctxt->rip_relative = 1;
} else {
@@ -1231,10 +1232,6 @@
adjust_modrm_seg(ctxt, base_reg);
}
switch (ctxt->modrm_mod) {
- case 0:
- if (ctxt->modrm_rm == 5)
- modrm_ea += insn_fetch(s32, ctxt);
- break;
case 1:
modrm_ea += insn_fetch(s8, ctxt);
break;