grub2/0238-bz1374141-fix-incorrect-mask-for-ppc64.patch

From 7412918d8716fc10e8ba64aa2c97f3e09a9f4569 Mon Sep 17 00:00:00 2001
From: Masahiro Matsuya <mmatsuya@redhat.com>
Date: Sat, 29 Oct 2016 08:35:26 +0900
Subject: [PATCH] bz1374141 fix incorrect mask for ppc64

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_swap_bytes32(grub_le_to_cpu32 (subnet_mask.ipv4))
0000 0000 0000 0000 0000 0011 1111 1111 # ~grub_swap_bytes32(grub_le_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)
---
 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 002446be1c3..3df75357a70 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_swap_bytes32(grub_le_to_cpu32 (subnet_mask.ipv4))));
     }
 
   if (gateway_addr.ipv4 != 0)