> On Jun 23, 2020, at 9:59 AM, Song Liu <songliubraving@xxxxxx> wrote:
>
>
>
>> On Jun 23, 2020, at 8:19 AM, Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote:
>>
>> On Tue, Jun 23, 2020 at 12:08 AM Song Liu <songliubraving@xxxxxx> wrote:
>>>
>
> [...]
>
>>>
>>> +BPF_CALL_3(bpf_get_task_stack_trace, struct task_struct *, task,
>>> + void *, entries, u32, size)
>>> +{
>>> + return stack_trace_save_tsk(task, (unsigned long *)entries, size, 0);
>>> +}
>>> +
>>> +static int bpf_get_task_stack_trace_btf_ids[5];
>>> +static const struct bpf_func_proto bpf_get_task_stack_trace_proto = {
>>> + .func = bpf_get_task_stack_trace,
>>> + .gpl_only = true,
>>
>> why?
>
> Actually, I am not sure when we should use gpl_only = true.
>
>>
>>> + .ret_type = RET_INTEGER,
>>> + .arg1_type = ARG_PTR_TO_BTF_ID,
>>> + .arg2_type = ARG_PTR_TO_MEM,
>>> + .arg3_type = ARG_CONST_SIZE_OR_ZERO,
>>
>> OR_ZERO ? why?
>
> Will fix.
>
>>
>>> + .btf_id = bpf_get_task_stack_trace_btf_ids,
>>> +};
>>> +
>>> static const struct bpf_func_proto *
>>> raw_tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>>> {
>>> @@ -1521,6 +1538,10 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>>> return prog->expected_attach_type == BPF_TRACE_ITER ?
>>> &bpf_seq_write_proto :
>>> NULL;
>>> + case BPF_FUNC_get_task_stack_trace:
>>> + return prog->expected_attach_type == BPF_TRACE_ITER ?
>>> + &bpf_get_task_stack_trace_proto :
>>
>> why limit to iter only?
>
> I guess it is also useful for other types. Maybe move to bpf_tracing_func_proto()?
>
>>
>>> + *
>>> + * int bpf_get_task_stack_trace(struct task_struct *task, void *entries, u32 size)
>>> + * Description
>>> + * Save a task stack trace into array *entries*. This is a wrapper
>>> + * over stack_trace_save_tsk().
>>
>> size is not documented and looks wrong.
>> the verifier checks it in bytes, but it's consumed as number of u32s.
>
> I am not 100% sure, but verifier seems check it correctly. And I think it is consumed
> as u64s?
I was wrong. Verifier checks as bytes. Will fix.
Song
