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Commit 5b38ab87 authored by Nadav Amit's avatar Nadav Amit Committed by Paolo Bonzini
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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: default avatarNadav Amit <namit@cs.technion.ac.il>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 4114c27d

arch/x86/kvm/emulate.c

+1 −4
Original line number Diff line number Diff line
@@ -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;