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KVM: x86: decode_modrm does not regard modrm correctly

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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>
This commit is contained in:
Nadav Amit 2014-11-02 11:54:41 +02:00 committed by Paolo Bonzini
parent 4114c27d45
commit 5b38ab877e
1 changed files with 1 additions and 4 deletions
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5
arch/x86/kvm/emulate.c
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@ -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;