netdev - Re: [PATCH bpf-next v2 7/8] tools: bpftool: refactor btf_dumper_int

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Message-ID: <20181215212625.raaqx5ypltzszqdg@kafai-mbp>
Date:   Sat, 15 Dec 2018 21:26:27 +0000
From:   Martin Lau <kafai@...com>
To:     Yonghong Song <yhs@...com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <Kernel-team@...com>
Subject: Re: [PATCH bpf-next v2 7/8] tools: bpftool: refactor
 btf_dumper_int_bits()

On Fri, Dec 14, 2018 at 03:34:33PM -0800, Yonghong Song wrote:
> The core dump funcitonality in btf_dumper_int_bits() is
> refactored into a separate function btf_dumper_bitfield()
> which will be used by the next patch.
> 
> Signed-off-by: Yonghong Song <yhs@...com>
> ---
>  tools/bpf/bpftool/btf_dumper.c | 22 ++++++++++++++++------
>  1 file changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/bpf/bpftool/btf_dumper.c b/tools/bpf/bpftool/btf_dumper.c
> index 5cdb2ef8b6f1..ec1da87c3d65 100644
> --- a/tools/bpf/bpftool/btf_dumper.c
> +++ b/tools/bpf/bpftool/btf_dumper.c
> @@ -73,20 +73,17 @@ static int btf_dumper_array(const struct btf_dumper *d, __u32 type_id,
>  	return ret;
>  }
>  
> -static void btf_dumper_int_bits(__u32 int_type, __u8 bit_offset,
> +static void btf_dumper_bitfield(__u32 nr_bits, __u8 bit_offset,
>  				const void *data, json_writer_t *jw,
>  				bool is_plain_text)
>  {
>  	int left_shift_bits, right_shift_bits;
> -	int nr_bits = BTF_INT_BITS(int_type);
> -	int total_bits_offset;
>  	int bytes_to_copy;
>  	int bits_to_copy;
>  	__u64 print_num;
>  
> -	total_bits_offset = bit_offset + BTF_INT_OFFSET(int_type);
> -	data += BITS_ROUNDDOWN_BYTES(total_bits_offset);
> -	bit_offset = BITS_PER_BYTE_MASKED(total_bits_offset);
> +	data += BITS_ROUNDDOWN_BYTES(bit_offset);
> +	bit_offset = BITS_PER_BYTE_MASKED(bit_offset);
>  	bits_to_copy = bit_offset + nr_bits;
>  	bytes_to_copy = BITS_ROUNDUP_BYTES(bits_to_copy);
>  
> @@ -109,6 +106,19 @@ static void btf_dumper_int_bits(__u32 int_type, __u8 bit_offset,
>  		jsonw_printf(jw, "%llu", print_num);
>  }
>  
> +
> +static void btf_dumper_int_bits(__u32 int_type, __u8 bit_offset,
> +				const void *data, json_writer_t *jw,
> +				bool is_plain_text)
> +{
> +	int nr_bits = BTF_INT_BITS(int_type);
> +	int total_bits_offset;
> +
> +	total_bits_offset = bit_offset + BTF_INT_OFFSET(int_type);
> +	btf_dumper_bitfield(nr_bits, total_bits_offset, data, jw,
The 2nd arg is "__u8 bit_offset".  Can you check if total_bits_offset
is fine here, considering BTF_INT_OFFSET() is 8 bits itself.
A comment would help if it is safe.

Other than that,
Acked-by: Martin KaFai Lau <kafai@...com>

> +			    is_plain_text);
> +}
> +
>  static int btf_dumper_int(const struct btf_type *t, __u8 bit_offset,
>  			  const void *data, json_writer_t *jw,
>  			  bool is_plain_text)
> -- 
> 2.17.1
>