Re: [PATCH] x86 emulator: Add IRET instruction

[Paolo Bonzini <pbonzini@redhat.com>]

On 07/26/2010 02:07 AM, Mohammed Gamal wrote:
> On Mon, Jul 26, 2010 at 2:59 AM, Paolo Bonzini<pbonzini@redhat.com>  wrote:
>> On 07/25/2010 09:20 PM, Mohammed Gamal wrote:
>>>
>>> +       if (c->op_bytes == 4)
>>> +               temp_eflags = ((temp_eflags & 0x257fd5) | (ctxt->eflags&
>>>   0x1a0000));
>>
>> Should this do also
>>
>> if (c->op_bytes == 2)
>>     temp_eflags = ((temp_eflags & 0x7fd5) | (ctxt->eflags & ~0xffffL));
>>
>> ?
>
> I don't think this is needed. The temp_eflags value is assigned
> directly to eflags if we're operand size is 16 bits. At least that's
> what the Intel manual says!

That's fine, but please make sure that

   mov %sp, %bp
   orw $2, 4(%bp)
   iret

followed at return site by

   pushf
   popw %ax

does not set bit 1 in %ax.  That's the important point (also see how 
emulate_popf avoids magic hex constants).

Paolo