Re: [Xen-devel] [PATCH for-4.5] pygrub: Fix regression from c/s d1b93ea, attempt 2

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-11-25 at 11:11 -0500, Boris Ostrovsky wrote:
> c/s d1b93ea causes substantial functional regressions in pygrub's ability to
> parse bootloader configuration files.
> 
> c/s d1b93ea itself changed an an interface which previously used exclusively
> integers, to using strings in the case of a grub configuration with explicit
> default set, along with changing the code calling the interface to require a
> string.  The default value for "default" remained as an integer.
> 
> As a result, any Extlinux or Lilo configuration (which drives this interface
> exclusively with integers), or Grub configuration which doesn't explicitly
> declare a default will die with an AttributeError when attempting to call
> "self.cf.default.isdigit()" where "default" is an integer.
> 
> Sadly, this AttributeError gets swallowed by the blanket ignore in the loop
> which searches partitions for valid bootloader configurations, causing the
> issue to be reported as "Unable to find partition containing kernel"
> 
> We should explicitly check type of "default" in image_index() and process it
> appropriately.
> 
> Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

In general I would prefer the first line of the commit message to be a
short description of the actual functional change and not a reference to
fixing some other commit, which is basically meaningless to anyone
reading the log even now, nevermind in six months. I think I'm going to
start picking up on this more frequently from now on.

CCing Konrad for RM input. I'm much less worried about corner cases etc
wrt the freeze etc than I was with the larger fix proposed earlier.

> ---
> 
> Commit message is Andrew's with exception of the last sentense.
> 
> I only tested this with grub2.
> 
> -boris
> 
>  tools/pygrub/src/pygrub |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
>  mode change 100644 => 100755 tools/pygrub/src/pygrub
> 
> diff --git a/tools/pygrub/src/pygrub b/tools/pygrub/src/pygrub
> old mode 100644
> new mode 100755
> index aa7e562..3ec52fd
> --- a/tools/pygrub/src/pygrub
> +++ b/tools/pygrub/src/pygrub
> @@ -457,7 +457,9 @@ class Grub:
>          self.cf.parse(buf)
>  
>      def image_index(self):
> -        if self.cf.default.isdigit():
> +        if isinstance(self.cf.default, int):
> +            sel = self.cf.default
> +        elif self.cf.default.isdigit():
>              sel = int(self.cf.default)
>          else:
>              # We don't fully support submenus. Look for the leaf value in



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