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

[Julien Grall <julien.grall@xxxxxxx>]

On 26/06/2016 10:30, Dirk Behme wrote:
> Hi Julien,
Hi Dirk,

> 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?
Yes, although I would drop the question marks at the end of the second 
sentence. We know that the kernel is too old.
Thank you for doing this.

Regards,

--
Julien Grall

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