netdev - Re: [PATCH bpf v2 1/1] bpf: btf: Fix bitfield extraction for big endian

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Message-ID: <20180710234528.2kj2kv7gjmigvvgp@kafai-mbp.dhcp.thefacebook.com>
Date:   Tue, 10 Jul 2018 16:46:16 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Okash Khawaja <osk@...com>
CC:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Yonghong Song <yhs@...com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        "David S. Miller" <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <kernel-team@...com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf v2 1/1] bpf: btf: Fix bitfield extraction for big
 endian

On Tue, Jul 10, 2018 at 02:33:07PM -0700, Okash Khawaja wrote:
> When extracting bitfield from a number, btf_int_bits_seq_show() builds
> a mask and accesses least significant byte of the number in a way
> specific to little-endian. This patch fixes that by checking endianness
> of the machine and then shifting left and right the unneeded bits.
> 
> Thanks to Martin Lau for the help in navigating potential pitfalls when
> dealing with endianess and for the final solution.
> 
> Fixes: b00b8daec828 ("bpf: btf: Add pretty print capability for data with BTF type info")
> Signed-off-by: Okash Khawaja <osk@...com>
Acked-by: Martin KaFai Lau <kafai@...com>