Re: [PATCH v3] xen: arm: Update arm64 image header

[Dirk Behme <dirk.behme@gmail.com>]

Hi Julien,

On 26.06.2016 10:29, Julien Grall wrote:
> Hello Dirk,
>
> On 26/06/2016 06:47, Dirk Behme wrote:
>> On 23.06.2016 17:18, Julien Grall wrote:
>>> On 23/06/16 07:38, Dirk Behme wrote:
>>>> +        uint64_t res2;
>>>>           uint64_t res3;
>>>>           uint64_t res4;
>>>> -        uint64_t res5;
>>>> -        uint32_t magic1;
>>>> -        uint32_t res6;
>>>> +        uint32_t magic;        /* Magic number, little endian,
>>>> "ARM\x64" */
>>>> +        uint32_t res5;
>>>>       } zimage;
>>>>       uint64_t start, end;
>>>>
>>>> @@ -354,20 +353,30 @@ static int kernel_zimage64_probe(struct
>>>> kernel_info *info,
>>>>
>>>>       copy_from_paddr(&zimage, addr, sizeof(zimage));
>>>>
>>>> -    if ( zimage.magic0 != ZIMAGE64_MAGIC_V0 &&
>>>> -         zimage.magic1 != ZIMAGE64_MAGIC_V1 )
>>>> +    if ( zimage.magic != ZIMAGE64_MAGIC ) {
>>>> +        printk(XENLOG_ERR "No valid magic found in header! Kernel
>>>> too old?\n");
>>>
>>> I have found why there were no error messages here before. The
>>> function kernel_probe will try the different formats supported one by
>>> one.
>>>
>>> So this message will be printed if the kernel is an ARM32 image, which
>>> will confuse the user. So I would print this message only when
>>> zimage.magic0 is equal to ZIMAGE64_MAGIC_V0.
>>
>>
>> Which we don't have with the recent header format any more.
>
> Well, we control the structure in Xen. So we could re-introduce the
> field magic0 through an union.
>
>  > This does
>> mean I drop this message again, as it doesn't make sense if the
>> magic is
>> used for the format detection.
>
> I would still prefer to keep an error message when only MAGIC_V0 is
> present. This will avoid people to spend time understanding why it
> does not work anymore.


This way

if ( zimage.magic != ZIMAGE64_MAGIC ) {
       if ( zimage.magic0 == ZIMAGE64_MAGIC_V0 )
             printk(XENLOG_ERR "No valid magic found in header! Kernel 
too old?\n");
       return -EINVAL;
}

with magic0 being a union with code0?

Best regards

Dirk


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