Re: [PATCH] KVM: emulator: implement AAD instruction

[Paolo Bonzini <pbonzini@redhat.com>]

Il 10/12/2012 10:42, Gleb Natapov ha scritto:
> Windows2000 uses it during boot. This fixes
> https://bugzilla.kernel.org/show_bug.cgi?id=50921
> 
> Signed-off-by: Gleb Natapov <gleb@redhat.com>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 39171cb..92c7292 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -2852,6 +2852,27 @@ static int em_das(struct x86_emulate_ctxt *ctxt)
>  	return X86EMUL_CONTINUE;
>  }
>  
> +static int em_aad(struct x86_emulate_ctxt *ctxt)
> +{
> +	u8 al = ctxt->dst.val & 0xff;
> +	u8 ah = (ctxt->dst.val >> 8) & 0xff;
> +
> +	al = (al + (ah * ctxt->src.val)) & 0xff;
> +
> +	ctxt->dst.val = (ctxt->dst.val & 0xffff0000) | al;
> +
> +	ctxt->eflags &= ~(X86_EFLAGS_PF | X86_EFLAGS_SF | X86_EFLAGS_ZF);
> +
> +	if (!al)
> +		ctxt->eflags |= X86_EFLAGS_ZF;
> +	if (!(al & 1))
> +		ctxt->eflags |= X86_EFLAGS_PF;

This is wrong, it should check the parity of al (even=1, odd=0).

Perhaps you can use the trick of em_das:

        /* Set PF, ZF, SF */
        ctxt->src.type = OP_IMM;
        ctxt->src.val = 0;
        ctxt->src.bytes = 1;
        emulate_2op_SrcV(ctxt, "or");

Paolo

> +	if (al & 0x80)
> +		ctxt->eflags |= X86_EFLAGS_SF;
> +
> +	return X86EMUL_CONTINUE;
> +}
> +
>  static int em_call(struct x86_emulate_ctxt *ctxt)
>  {
>  	long rel = ctxt->src.val;
> @@ -3801,7 +3822,7 @@ static const struct opcode opcode_table[256] = {
>  	D(ImplicitOps | No64), II(ImplicitOps, em_iret, iret),
>  	/* 0xD0 - 0xD7 */
>  	D2bv(DstMem | SrcOne | ModRM), D2bv(DstMem | ModRM),
> -	N, N, N, N,
> +	N, I(DstAcc | SrcImmByte | No64, em_aad), N, N,
>  	/* 0xD8 - 0xDF */
>  	N, N, N, N, N, N, N, N,
>  	/* 0xE0 - 0xE7 */
> --
> 			Gleb.
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>