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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Masahiro Matsuya <mmatsuya@redhat.com>
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Date: Sat, 29 Oct 2016 08:35:26 +0900
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Subject: [PATCH] bz1374141 fix incorrect mask for ppc64
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The netmask configured in firmware is not respected on ppc64 (big endian).
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When 255.255.252.0 is set as netmask in firmware, the following is the value of bootpath string in grub_ieee1275_parse_bootpath().
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 /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
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The netmask in this bootpath is no problem, since it's a value specified in firmware. But,
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The value of 'subnet_mask.ipv4' was set with 0xfffffc00, and __builtin_ctz (~grub_le_to_cpu32 (subnet_mask.ipv4)) returned 16 (not 22).
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As a result, 16 was used for netmask wrongly.
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1111 1111 1111 1111 1111 1100 0000 0000 # subnet_mask.ipv4 (=0xfffffc00)
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0000 0000 1111 1100 1111 1111 1111 1111 # grub_le_to_cpu32 (subnet_mask.ipv4)
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1111 1111 0000 0011 0000 0000 0000 0000 # ~grub_le_to_cpu32 (subnet_mask.ipv4)
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And, the count of zero with __builtin_ctz can be 16.
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This patch changes it as below.
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1111 1111 1111 1111 1111 1100 0000 0000 # subnet_mask.ipv4 (=0xfffffc00)
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0000 0000 1111 1100 1111 1111 1111 1111 # grub_le_to_cpu32 (subnet_mask.ipv4)
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1111 1111 1111 1111 1111 1100 0000 0000 # grub_swap_bytes32(grub_le_to_cpu32 (subnet_mask.ipv4))
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0000 0000 0000 0000 0000 0011 1111 1111 # ~grub_swap_bytes32(grub_le_to_cpu32 (subnet_mask.ipv4))
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The count of zero with __builtin_clz can be 22. (clz counts the number of one bits preceding the most significant zero bit)
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---
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 grub-core/net/drivers/ieee1275/ofnet.c | 3 +--
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 1 file changed, 1 insertion(+), 2 deletions(-)
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diff --git a/grub-core/net/drivers/ieee1275/ofnet.c b/grub-core/net/drivers/ieee1275/ofnet.c
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index ac4e62a95c9..3860b6f78d8 100644
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--- a/grub-core/net/drivers/ieee1275/ofnet.c
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+++ b/grub-core/net/drivers/ieee1275/ofnet.c
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@@ -220,8 +220,7 @@ grub_ieee1275_parse_bootpath (const char *devpath, char *bootpath,
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                                  flags);
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       inter->vlantag = vlantag;
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       grub_net_add_ipv4_local (inter,
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-                          __builtin_ctz (~grub_le_to_cpu32 (subnet_mask.ipv4)));
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-
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+                          __builtin_clz (~grub_swap_bytes32(grub_le_to_cpu32 (subnet_mask.ipv4))));
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     }
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   if (gateway_addr.ipv4 != 0)