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net/drivers/ieee1275/ofnet: Fix incorrect netmask

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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 not a 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>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Masahiro Matsuya 2022-08-24 13:36:37 -04:00 committed by Daniel Kiper
parent 170f17734a
commit 2c1425b8f0
1 changed files with 1 additions and 2 deletions
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3
grub-core/net/drivers/ieee1275/ofnet.c
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@ -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)