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

[Dirk Behme <dirk.behme@xxxxxxxxx>]

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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