> On Nov 6, 2020, at 3:18 PM, Martin Lau <kafai@xxxxxx> wrote:
>
> On Fri, Nov 06, 2020 at 02:59:14PM -0800, Song Liu wrote:
>>
>>
>>> On Nov 6, 2020, at 2:08 PM, Martin KaFai Lau <kafai@xxxxxx> wrote:
>>>
[...]
>>> +static bool bpf_sk_storage_tracing_allowed(const struct bpf_prog *prog)
>>> +{
>>> + const struct btf *btf_vmlinux;
>>> + const struct btf_type *t;
>>> + const char *tname;
>>> + u32 btf_id;
>>> +
>>> + if (prog->aux->dst_prog)
>>> + return false;
>>> +
>>> + /* Ensure the tracing program is not tracing
>>> + * any *sk_storage*() function and also
>>> + * use the bpf_sk_storage_(get|delete) helper.
>>> + */
>>> + switch (prog->expected_attach_type) {
>>> + case BPF_TRACE_RAW_TP:
>>> + /* bpf_sk_storage has no trace point */
>>> + return true;
>>> + case BPF_TRACE_FENTRY:
>>> + case BPF_TRACE_FEXIT:
>>> + btf_vmlinux = bpf_get_btf_vmlinux();
>>> + btf_id = prog->aux->attach_btf_id;
>>> + t = btf_type_by_id(btf_vmlinux, btf_id);
>>
>> What happens to fentry/fexit attach to other BPF programs? I guess
>> we should check for t == NULL?
> It does not support tracing BPF program and using bpf_sk_storage
> at the same time for now, so there is a "if (prog->aux->dst_prog)" test earlier.
> It could be extended to do it later as a follow up.
> I missed to mention that in the commit message.
>
> "t" should not be NULL here when tracing a kernel function.
> The verifier should have already checked it and ensured "t" is a FUNC.
Ah, I missed the dst_prog check. Thanks for the explanation.
Acked-by: Song Liu <songliubraving@xxxxxx>
