Re: [PATCH v3 bpf-next 5/5] selftests/bpf: Add bench for task storage creation

[Martin KaFai Lau <martin.lau@linux.dev>]

On 3/27/23 8:51 PM, James Hilliard wrote:
>> diff --git a/tools/testing/selftests/bpf/progs/bench_local_storage_create.c b/tools/testing/selftests/bpf/progs/bench_local_storage_create.c
>> index 2814bab54d28..7c851c9d5e47 100644
>> --- a/tools/testing/selftests/bpf/progs/bench_local_storage_create.c
>> +++ b/tools/testing/selftests/bpf/progs/bench_local_storage_create.c
>> @@ -22,6 +22,13 @@ struct {
>>          __type(value, struct storage);
>>   } sk_storage_map SEC(".maps");
>>
>> +struct {
>> +       __uint(type, BPF_MAP_TYPE_TASK_STORAGE);
>> +       __uint(map_flags, BPF_F_NO_PREALLOC);
>> +       __type(key, int);
>> +       __type(value, struct storage);
>> +} task_storage_map SEC(".maps");
>> +
>>   SEC("raw_tp/kmalloc")
>>   int BPF_PROG(kmalloc, unsigned long call_site, const void *ptr,
>>               size_t bytes_req, size_t bytes_alloc, gfp_t gfp_flags,
>> @@ -32,6 +39,24 @@ int BPF_PROG(kmalloc, unsigned long call_site, const void *ptr,
>>          return 0;
>>   }
>>
>> +SEC("tp_btf/sched_process_fork")
>> +int BPF_PROG(fork, struct task_struct *parent, struct task_struct *child)
> 
> Apparently fork is a built-in function in bpf-gcc:

It is also failing in a plain C program

#>  gcc -Werror=builtin-declaration-mismatch -o test test.c
test.c:14:35: error: conflicting types for built-in function ‘fork’; expected 
‘int(void)’ [-Werror=builtin-declaration-mismatch]
    14 | int __attribute__((__noinline__)) fork(long x, long y)
       |                                   ^~~~
cc1: some warnings being treated as errors

#> clang -o test test.c
succeed

I am not too attached to the name but it seems something should be addressed in 
the gcc instead.

> 
> In file included from progs/bench_local_storage_create.c:6:
> progs/bench_local_storage_create.c:43:14: error: conflicting types for
> built-in function 'fork'; expected 'int(void)'
> [-Werror=builtin-declaration-mismatch]
>     43 | int BPF_PROG(fork, struct task_struct *parent, struct
> task_struct *child)
>        |              ^~~~
> 
> I haven't been able to find this documented anywhere however.