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

[Julien Grall <julien.grall@xxxxxxx>]

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.
Regards,

--
Julien Grall

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