Re: [PATCH] xen: look for Xen notes in section headers too

[Daniel Kiper]

On Thu, Mar 14, 2019 at 08:52:45PM +0100, Marek Marczykowski-Górecki wrote:
> On Thu, Mar 14, 2019 at 01:39:43PM +0100, Daniel Kiper wrote:
> > On Thu, Mar 14, 2019 at 02:57:08AM +0100, Marek Marczykowski-Górecki wrote:
> > > Mirror behaviour of elf loader in libxc: first look for Xen notes in
> > > PT_NOTE segment, then in SHT_NOTE section and only then fallback to
> > > a section with __xen_guest name.
> > > This fixes loading PV kernels that Xen note have outside of PT_NOTE.
> > > While this may be result of a buggy linker script, loading such kernel
> > > directly works fine, so make it work with grub too.
> > > Specifically, this applies to binaries built from Unikraft.
> > >
> > > Signed-off-by: Marek Marczykowski-Górecki <address@hidden>
> >
> > I treat this as a fix, so, Reviewed-by: Daniel Kiper <address@hidden>
> >
> > However, ...
> >
> > > ---
> > >  grub-core/loader/i386/xen_fileXX.c | 15 +++++++++++++++
> > >  1 file changed, 15 insertions(+)
> > >
> > > diff --git a/grub-core/loader/i386/xen_fileXX.c 
> > > b/grub-core/loader/i386/xen_fileXX.c
> > > index fb66e66fe..6af6cc0da 100644
> > > --- a/grub-core/loader/i386/xen_fileXX.c
> > > +++ b/grub-core/loader/i386/xen_fileXX.c
> > > @@ -344,6 +344,21 @@ grub_xen_get_infoXX (grub_elf_t elf, struct 
> > > grub_xen_file_info *xi)
> > >    s = (Elf_Shdr *) ((char *) s0 + elf->ehdr.ehdrXX.e_shstrndx * 
> > > shentsize);
> > >    stroff = s->sh_offset;
> > >
> > > +  for (s = s0; s < (Elf_Shdr *) ((char *) s0 + shnum * shentsize);
> > > +       s = (Elf_Shdr *) ((char *) s + shentsize))
> > > +    {
> > > +      if (s->sh_type == SHT_NOTE) {
> >
> > Curly bracket is in wrong place...
> >
> > > + err = parse_note (elf, xi, s->sh_offset, s->sh_size);
> > > + if (err)
> > > +   goto cleanup;
> > > +      }
> >
> > ... and this is also in wrong place.
> >
> > > +    }
> > > +
> > > +  if (xi->has_note) {
> > > +    err = GRUB_ERR_NONE;
> > > +    goto cleanup;
> > > +  }
> >
> > Ditto. Next time please double check that you have correct formatting.
> > Now I will fix it before the push. If there are no objections then it
> > will happen at the beginning of next week.
>
> Thanks. This code style is very different than any other project I
> contribute to...

Yeah, I know how it works.

> Anyway, there is a comment earlier in this function:
>
>     /* FIXME: check note.  */
>
> Is it about this very issue and now can be removed?

Hmmm... I am not sure. I am not the author of this comment.
I think that I would leave it as is if we are not sure.

Daniel