Re: [RFC PATCH bpf-next v2 1/2] libbpf: support selective kernel module BTF loading via .kmod_btfs section

On 8/13/2026 11:37 AM, [email protected] wrote:
> Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
> - [Medium] Missing increment of `nr_loaded` prevents early loop termination.
> - [Low] Multi-line comment formatting violation.
> --
> 
> --- Patch [1]: [RFC PATCH bpf-next v2 1/2] libbpf: support selective kernel module BTF loading via .kmod_btfs section ---
> commit 3f4fb04bbfb95d7f7ea0012b5651135983af6e62
> Author: Fuyu Zhao <[email protected]>
> 
> libbpf: support selective kernel module BTF loading via .kmod_btfs section
> 
> This patch adds support for a ".kmod_btfs" ELF section to allow BPF programs
> to specify which kernel modules need BTF loading. It introduces functions to
> collect the module names and filter the BTF loading process to avoid loading
> unneeded modules.
> 
>> diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
>> index 9d160b5b9c0ee..171ea055cd323 100644
>> --- a/tools/lib/bpf/bpf_helpers.h
>> +++ b/tools/lib/bpf/bpf_helpers.h
>> @@ -188,6 +188,20 @@ enum libbpf_tristate {
>>  	TRI_MODULE = 2,
>>  };
>>  
>> +/* Helper typedef for declaring kernel module names that need BTF loading.
>> + *
> 
> [Severity: Low]
> This isn't a bug, but the BPF subsystem coding style expects multi-line
> comments to have the opening /* on its own line. Should this be reformatted
> to match the preferred kernel style?
> 

Thanks. I'll also fix the comment formatting.

>> + * Usage: define an array in the ".kmod_btfs" ELF section to specify
>> + * which modules need BTF loading:
>> + *
> 
> [ ... ]
> 
>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>> index 514e4e9daa825..9fe8a653e8b6b 100644
>> --- a/tools/lib/bpf/libbpf.c
>> +++ b/tools/lib/bpf/libbpf.c
> 
> [ ... ]
> 
>> @@ -5891,6 +5987,10 @@ static int load_module_btfs(struct bpf_object *obj)
>>  			break;
>>  		}
>>  		obj->btf_module_cnt++;
>> +
>> +		if (obj->kmod_btfs &&
>> +		    obj->kmod_btfs->nr_names == obj->kmod_btfs->nr_loaded)
>> +			break;
> 
> [Severity: Medium]
> Is obj->kmod_btfs->nr_loaded missing an increment?
> 
> Looking at the loop in load_module_btfs(), when a module BTF is successfully
> loaded and obj->btf_module_cnt is incremented, obj->kmod_btfs->nr_loaded
> doesn't appear to be updated anywhere.
> 
> Will this prevent the intended optimization of breaking out of the loop early,
> causing it to always scan all remaining kernel BTF IDs unnecessarily?
> 

My bad, this is a simple oversight. I forgot to preserve the
nr_loaded increment when removing KMODS_BTF_* and simplifying the
related logic. I'll fix it and pay closer attention to such changes
next time.

>>  	}
>>  
>>  	if (err) {
>