pyGrub: Fix default when out of range

Hi,
this is the patch to fix pyGrub default value when it's being set out of range. This patch makes the quiet and interactive mode select the same default image when the default value for boot entry is out of range, i.e. when the guest is having wrong configuration in it's boot loader (like 3 entries with default mistakenly set to 10 etc).

When the boot entry number is being set out of range it falls back to 0 (first entry of boot loader).

Michal

Michal Novotny<[email protected]>, RHCE
Virtualization Team (xen userspace), Red Hat

diff -r 7b00193bd033 tools/pygrub/src/pygrub
@@ -415,6 +415,9 @@ class Grub:
         timeout = int(self.cf.timeout)
 
         self.selected_image = self.cf.default
+        # If the selected (default) image doesn't exist we select the first entry
+        if self.selected_image > len(self.cf.images):
+            self.selected_image = 0
         self.isdone = False
         while not self.isdone:
             self.run_main(timeout)

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Michal Novotny writes ("[Xen-devel] [PATCH] pyGrub: Fix default when out of range"):

I'm not sure this is right. What does grub proper do with invalid defaults ? Is it really correct to blunder on and just use the first one as a default ?

Sorry to quibble.

Ian.

Hi Ian,
I did try it using the real (bare-metal) grub 0.97 (in RHEL-5) to set the default out of range and it was set to the first entry so it matches the bare-metal grub behavior now. So the quiet mode was having it right all the time but interactive mode didn't so this is basically fix for interactive mode of pygrub.

Michal

Michal Novotny<[email protected]>, RHCE
Virtualization Team (xen userspace), Red Hat

Michal Novotny writes ("Re: [Xen-devel] [PATCH] pyGrub: Fix default when out of range"):

Excellent, thanks for the clarification. I have applied your patch.

Ian.