[Libguestfs] [PATCH] Fix architecture detection of Linux guests with invalid grub.conf

[Matthew Booth]

If a Linux guest's grub.conf contained a default kernel which referred to
non-existent kernel, architecture detection would default to i686. For an x86_64
guest, the result would not boot.

This change uses the first grub.conf entry if the default is invalid or not
present, and falls back to the architecture detected by inspection otherwise. If
neither of these yield an architecture, it defaults to x86_64 instead of i686 as
a more conservative default.

Fixes RHBZ#623579
---
 lib/Sys/VirtV2V/Converter/RedHat.pm |   21 ++++++++++++---------
 1 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/lib/Sys/VirtV2V/Converter/RedHat.pm b/lib/Sys/VirtV2V/Converter/RedHat.pm
index 78a454a..a8a7051 100644
--- a/lib/Sys/VirtV2V/Converter/RedHat.pm
+++ b/lib/Sys/VirtV2V/Converter/RedHat.pm
@@ -610,17 +610,20 @@ sub _get_os_arch
     my $boot = $desc->{boot};
     my $default_boot = $boot->{default} if(defined($boot));
 
-    my $arch;
-    if(defined($default_boot)) {
-        my $config = $boot->{configs}->[$default_boot];
+    # Pick the default config if one is defined
+    my $config = $boot->{configs}->[$default_boot] if defined($default_boot);
 
-        if(defined($config->{kernel})) {
-            $arch = $config->{kernel}->{arch};
-        }
-    }
+    # Pick the first defined config if there is no default, or it is invalid
+    $config = $boot->{configs}[0] unless defined($config);
+
+    my $arch = $config->{kernel}->{arch}
+        if defined($config) && defined($config->{kernel});
+
+    # Use the libguestfs-detected arch if the above failed
+    $arch = $desc->{arch} unless defined($arch);
 
-    # Default to i686 if we didn't find an architecture
-    return 'i686' if(!defined($arch));
+    # Default to x86_64 if we still didn't find an architecture
+    return 'x86_64' unless defined($arch);
 
     # We want an i686 guest for i[345]86
     return 'i686' if($arch =~ /^i[345]86$/);
-- 
1.7.3.4