Re: [RFC PATCH bpf-next v5 2/2] net: Add additional bit to support clockid_t timestamp type

Abhishek Chauhan (ABC)
2024-05-03T22:15:28Z

On 5/3/2024 2:41 PM, Martin KaFai Lau wrote:
> On 5/3/24 2:33 PM, Abhishek Chauhan (ABC) wrote:
>>
>>> BPF_CALL_3(bpf_skb_set_tstamp, struct sk_buff *, skb,
>>>             u64, tstamp, u32, tstamp_type)
>>> {
>>>      /* ... */
>>>      case BPF_SKB_CLOCK_TAI:
>>>          if (!tstamp)
>>>              return -EINVAL;
>>>          skb->tstamp = tstamp;
>>>          skb->tstamp_type = SKB_CLOCK_TAI;
>>>          break;
>>>          case BPF_SKB_CLOCK_REALTIME:
>>>          skb->tstamp = tstamp;
>>>          skb->tstamp_type = SKB_CLOCK_REALTIME;
>>>          break;
>>>
>>>      /* ... */
>>> }
>>>
>>>>                return -EINVAL;
>>>
>>>> @@ -9388,17 +9394,17 @@ static struct bpf_insn *bpf_convert_tstamp_type_read(const struct bpf_insn *si,
>>>>    {
>>>>        __u8 value_reg = si->dst_reg;
>>>>        __u8 skb_reg = si->src_reg;
>>>> -    /* AX is needed because src_reg and dst_reg could be the same */
>>>> -    __u8 tmp_reg = BPF_REG_AX;
>>>> -
>>>> -    *insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg,
>>>> -                  SKB_BF_MONO_TC_OFFSET);
>>>> -    *insn++ = BPF_JMP32_IMM(BPF_JSET, tmp_reg,
>>>> -                SKB_MONO_DELIVERY_TIME_MASK, 2);
>>>> -    *insn++ = BPF_MOV32_IMM(value_reg, BPF_SKB_TSTAMP_UNSPEC);
>>>> -    *insn++ = BPF_JMP_A(1);
>>>> -    *insn++ = BPF_MOV32_IMM(value_reg, BPF_SKB_TSTAMP_DELIVERY_MONO);
>>>> -
>>>> +    BUILD_BUG_ON(__SKB_CLOCK_MAX != BPF_SKB_TSTAMP_DELIVERY_TAI);
>>>
>>> Add these also:
>>>
>>>      BUILD_BUG_ON(SKB_CLOCK_REALTIME != BPF_SKB_CLOCK_REALTIME);
>>>      BUILD_BUG_ON(SKB_CLOCK_MONOTONIC != BPF_SKB_CLOCK_MONOTONIC);
>>>      BUILD_BUG_ON(SKB_CLOCK_TAI != BPF_SKB_CLOCK_TAI);
>>>
>>
>> Martin, The above suggestion of adding BUILD_BUG_ON always gives me a warning stating the following.
>>
>> Some systems considers warning as error if compiler flags are enabled. I believe this requires your suggestion before i raise RFC v6 patchset to either keep the
>> BUILD_BUG_ON or remove it completely.
>
> cast it?
>
Thanks Martin. Will do the same. Casting worked for me!.

>>
>> /local/mnt/workspace/kernel_master/linux-next/net/core/filter.c:9395:34: warning: comparison between ‘enum skb_tstamp_type’ and ‘enum <anonymous>’ [-Wenum-compare]
>>   9395 |  BUILD_BUG_ON(SKB_CLOCK_REALTIME != BPF_SKB_CLOCK_REALTIME);
>>        |                                  ^~
>> /local/mnt/workspace/kernel_master/linux-next/include/linux/compiler_types.h:451:9: note: in definition of macro ‘__compiletime_assert’
>>    451 |   if (!(condition))     \
>>        |         ^~~~~~~~~
>> /local/mnt/workspace/kernel_master/linux-next/include/linux/compiler_types.h:471:2: note: in expansion of macro ‘_compiletime_assert’
>>    471 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
>>        |  ^~~~~~~~~~~~~~~~~~~
>> /local/mnt/workspace/kernel_master/linux-next/include/linux/build_bug.h:39:37: note: in expansion of macro ‘compiletime_assert’
>>     39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
>>        |                                     ^~~~~~~~~~~~~~~~~~
>> /local/mnt/workspace/kernel_master/linux-next/include/linux/build_bug.h:50:2: note: in expansion of macro ‘BUILD_BUG_ON_MSG’
>>     50 |  BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
>>        |  ^~~~~~~~~~~~~~~~
>> /local/mnt/workspace/kernel_master/linux-next/net/core/filter.c:9395:2: note: in expansion of macro ‘BUILD_BUG_ON’
>>   9395 |  BUILD_BUG_ON(SKB_CLOCK_REALTIME != BPF_SKB_CLOCK_REALTIME);
>>        |  ^~~~~~~~~~~~
>> /local/mnt/workspace/kernel_master/linux-next/net/core/filter.c:9396:35: warning: comparison between ‘enum skb_tstamp_type’ and ‘enum <anonymous>’ [-Wenum-compare]
>>   9396 |  BUILD_BUG_ON(SKB_CLOCK_MONOTONIC != BPF_SKB_CLOCK_MONOTONIC);
>>        |                                   ^~
>> /local/mnt/workspace/kernel_master/linux-next/include/linux/compiler_types.h:451:9: note: in definition of macro ‘__compiletime_assert’
>>    451 |   if (!(condition))     \
>>        |         ^~~~~~~~~
>>
>>           |                                      ^~
>>
>>
>>
>