[PATCH v2] net/drivers/ieee1275/ofnet: fix incorrect netmask

[Robbie Harwood]

From: Masahiro Matsuya <mmatsuya@redhat.com>

The netmask configured in firmware is not respected on ppc64 (big
endian).  When 255.255.252.0 is set as netmask in firmware, the
following is the value of bootpath string in
grub_ieee1275_parse_bootpath():

/vdevice/l-lan@30000002:speed=auto,duplex=auto,192.168.88.10,,192.168.89.113,192.168.88.1,5,5,255.255.252.0,512

The netmask in this bootpath is no problem, since it's a value specified
in firmware.  But the value of 'subnet_mask.ipv4' was set with
0xfffffc00, and __builtin_ctz (~grub_le_to_cpu32 (subnet_mask.ipv4))
returned 16 (not 22).  As a result, 16 was used for netmask wrongly:

1111 1111 1111 1111 1111 1100 0000 0000 # subnet_mask.ipv4 (=0xfffffc00)
0000 0000 1111 1100 1111 1111 1111 1111 # grub_le_to_cpu32 (subnet_mask.ipv4)
1111 1111 0000 0011 0000 0000 0000 0000 # ~grub_le_to_cpu32 (subnet_mask.ipv4)

and the count of zero with __builtin_ctz can be 16.  This patch changes
it as below:

1111 1111 1111 1111 1111 1100 0000 0000 # subnet_mask.ipv4 (=0xfffffc00)
0000 0000 1111 1100 1111 1111 1111 1111 # grub_le_to_cpu32 (subnet_mask.ipv4)
1111 1111 1111 1111 1111 1100 0000 0000 # grub_be_to_cpu32 (subnet_mask.ipv4)
0000 0000 0000 0000 0000 0011 1111 1111 # ~grub_be_to_cpu32 (subnet_mask.ipv4)

The count of zero with __builtin_clz can be 22.  (clz counts the number
of one bits preceding the most significant zero bit)

Signed-off-by: Masahiro Matsuya <mmatsuya@redhat.com>
Signed-off-by: Robbie Harwood <rharwood@redhat.com>
---
 grub-core/net/drivers/ieee1275/ofnet.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/grub-core/net/drivers/ieee1275/ofnet.c 
b/grub-core/net/drivers/ieee1275/ofnet.c
index 8c8398948b..78f03df8e2 100644
--- a/grub-core/net/drivers/ieee1275/ofnet.c
+++ b/grub-core/net/drivers/ieee1275/ofnet.c
@@ -220,8 +220,7 @@ grub_ieee1275_parse_bootpath (const char *devpath, char 
*bootpath,
                                  flags);
       inter->vlantag = vlantag;
       grub_net_add_ipv4_local (inter,
-                          __builtin_ctz (~grub_le_to_cpu32 
(subnet_mask.ipv4)));
-
+                          __builtin_clz (~grub_be_to_cpu32 
(subnet_mask.ipv4)));
     }
 
   if (gateway_addr.ipv4 != 0)
-- 
2.35.1