Re: [PATCH bpf-next 1/4] bpf: Allow get_func_[arg|arg_cnt] helpers in raw tracepoint programs

[Leon Hwang]

On 2025/5/12 23:25, Alexei Starovoitov wrote:
> On Mon, May 12, 2025 at 4:12 AM Leon Hwang <leon.hw...@linux.dev> wrote:
>>

[...]

>>
>> However, since bpf_rdonly_cast() is a kfunc, it causes registers r1–r5
>> to be considered volatile.
> 
> It is not.
> See:
> BTF_ID_FLAGS(func, bpf_rdonly_cast, KF_FASTCALL)
> and relevant commits.

Thanks for the reminder — you're right, bpf_rdonly_cast() is marked with
KF_FASTCALL, so it doesn't make r1–r5 volatile.

Thanks,
Leon