Re: [PATCH v9 12/13] test_x86_emulator.c: Add tests for #GP usage

[Don Slutz <dslutz@verizon.com>]

On 02/25/15 03:30, Jan Beulich wrote:
>>>> On 24.02.15 at 19:29, <dslutz@verizon.com> wrote:
>> +    /*
>> +     * Test out special #GP handling for the VMware port 0x5658.
>> +     * This is done in two "modes", j=0 and j=1.  Testing 4
>> +     * instructions (all the basic PIO) in both modes.
>> +     *
>> +     * The port used is based on j.
>> +     *
>> +     * For IN, eax should change.  For OUT eax should not change.
>> +     *
>> +     * All 4 PIO instructions are 1 byte long, so eip should only
>> +     * change by 1.
>> +     */
> 
> Thanks, this looks reasonable.
> 
>> +        /*
>> +         * In j=0, there should not be an error returned.
>> +         * In j=1, there should be an error returned.
>> +         */
>> +        if ( rc != X86EMUL_OKAY )
>> +        {
>> +            if ( j == 0 )
>> +                goto fail;
>> +        }
>> +        else if ( j == 1 )
>> +            goto fail;
> 
> I'd appreciate if this could be expressed in a little fewer lines. I'm not
> sure
> 
>     if ( (rc == X86EMUL_OKAY) == j )
>         goto fail;
> 
> would be deemed readable, but surely
> 
>     if ( rc == X86EMUL_OKAY ? j : !j )
>         goto fail;
> 
> would suffice.

Tried this and it works fine, so switching to:

+        if ( rc == X86EMUL_OKAY ? j : !j )


   -Don Slutz


>> So I have checked and read, write_gp, cmpxchg_gp, read_segment,
>> and inject_hw_exception are not needed.  So that leaves:
>>
>> static struct x86_emulate_ops emulops_gp = {
>>     .insn_fetch = fetch,
>>     .read_io    = read_io,
>>     .write_io   = write_io,
>>     .vmport_check = vmport_check,
>> };
> 
> Quite a bit better, thanks.
> 
> Jan
>