Please don't chain swap_bytes32 with le_to_cpu32 as it's a less readable
equivalent of be_to_cpu32

On Thu, 31 Oct 2019, 11:38 Javier Martinez Canillas, <javi...@redhat.com>
wrote:

> From: Masahiro Matsuya <mmats...@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_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)
>
> Signed-off-by: Masahiro Matsuya <mmats...@redhat.com>
> Signed-off-by: Javier Martinez Canillas <javi...@redhat.com>
> ---
>
>  grub-core/net/drivers/ieee1275/ofnet.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git grub-core/net/drivers/ieee1275/ofnet.c
> grub-core/net/drivers/ieee1275/ofnet.c
> index ac4e62a95c9..3860b6f78d8 100644
> --- grub-core/net/drivers/ieee1275/ofnet.c
> +++ 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)
> --
> 2.21.0
>
>
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> Grub-devel@gnu.org
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>
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