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 (file)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1223,6 +1223,7 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
                        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 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
                        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;