On 12/15/18 1:26 PM, Martin Lau wrote:
> 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 <y...@fb.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.
This should be okay.
In kernel btf_int_check_meta, we have
nr_bits = BTF_INT_BITS(int_data) + BTF_INT_OFFSET(int_data);
if (nr_bits > BITS_PER_U64) {
btf_verifier_log_type(env, t, "nr_bits exceeds %zu",
BITS_PER_U64);
return -EINVAL;
}
So BTF_INT_OFFSET(int_data) at most BITS_PER_U64.
bit_offset at most 7, so total_bits_offset still within range.
kernel has similar implementation.
I will add a comment here.
>
> Other than that,
> Acked-by: Martin KaFai Lau <ka...@fb.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
>>
