Re: [PATCH bpf-next v2 17/18] selftests/bpf: add basic testcases for tracing_multi

[Ihor Solodrai <ihor.solodrai@linux.dev>]

On 7/15/25 5:31 PM, Alexei Starovoitov wrote:
> On Tue, Jul 15, 2025 at 5:27 PM Ihor Solodrai <ihor.solodrai@linux.dev> wrote:
>>
>> On 7/14/25 4:49 PM, Ihor Solodrai wrote:
>>> On 7/8/25 1:07 PM, Alexei Starovoitov wrote:
>>>> On Thu, Jul 3, 2025 at 5:18 AM Menglong Dong
>>>> <menglong8.dong@gmail.com> wrote:
>>>>>
>>>>> +               return true;
>>>>> +
>>>>> +       /* Following symbols have multi definition in kallsyms, take
>>>>> +        * "t_next" for example:
>>>>> +        *
>>>>> +        *     ffffffff813c10d0 t t_next
>>>>> +        *     ffffffff813d31b0 t t_next
>>>>> +        *     ffffffff813e06b0 t t_next
>>>>> +        *     ffffffff813eb360 t t_next
>>>>> +        *     ffffffff81613360 t t_next
>>>>> +        *
>>>>> +        * but only one of them have corresponding mrecord:
>>>>> +        *     ffffffff81613364 t_next
>>>>> +        *
>>>>> +        * The kernel search the target function address by the symbol
>>>>> +        * name "t_next" with kallsyms_lookup_name() during attaching
>>>>> +        * and the function "0xffffffff813c10d0" can be matched, which
>>>>> +        * doesn't have a corresponding mrecord. And this will make
>>>>> +        * the attach failing. Skip the functions like this.
>>>>> +        *
>>>>> +        * The list maybe not whole, so we still can fail......We need a
>>>>> +        * way to make the whole things right. Yes, we need fix it :/
>>>>> +        */
>>>>> +       if (!strcmp(name, "kill_pid_usb_asyncio"))
>>>>> +               return true;
>>>>> +       if (!strcmp(name, "t_next"))
>>>>> +               return true;
>>>>> +       if (!strcmp(name, "t_stop"))
>>>>> +               return true;
>>
>> This little patch will filter out from BTF any static functions with
>> the same name that appear more than once.
>>
>> diff --git a/btf_encoder.c b/btf_encoder.c
>> index 0bc2334..6441269 100644
>> --- a/btf_encoder.c
>> +++ b/btf_encoder.c
>> @@ -96,7 +96,8 @@ struct elf_function {
>>           const char      *name;
>>           char            *alias;
>>           size_t          prefixlen;
>> -       bool            kfunc;
>> +       uint8_t         is_static:1;
>> +       uint8_t         kfunc:1;
>>           uint32_t        kfunc_flags;
>>    };
>>
>> @@ -1374,7 +1375,7 @@ static int saved_functions_combine(struct
>> btf_encoder_func_state *a, struct btf_
>>                   return ret;
>>           optimized = a->optimized_parms | b->optimized_parms;
>>           unexpected = a->unexpected_reg | b->unexpected_reg;
>> -       inconsistent = a->inconsistent_proto | b->inconsistent_proto;
>> +       inconsistent = a->inconsistent_proto | b->inconsistent_proto |
>> a->elf->is_static | b->elf->is_static;
>>           if (!unexpected && !inconsistent && !funcs__match(a, b))
>>                   inconsistent = 1;
>>           a->optimized_parms = b->optimized_parms = optimized;
>> @@ -1461,6 +1462,8 @@ static void elf_functions__collect_function(struct
>> elf_functions *functions, GEl
>>
>>           func = &functions->entries[functions->cnt];
>>           func->name = name;
>> +       func->is_static = elf_sym__bind(sym) == STB_LOCAL;
>> +
> 
> Hmm. We definitely don't want to filter out all static functions.
> That's too drastic.

Not all static functions. Only those that match by name.