2021-07-23 10:18 UTC-0700 ~ Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> > On Fri, Jul 23, 2021 at 9:13 AM Quentin Monnet <quentin@xxxxxxxxxxxxx> wrote: >> >> 2021-07-23 08:54 UTC-0700 ~ Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> >>> On Fri, Jul 23, 2021 at 2:31 AM Quentin Monnet <quentin@xxxxxxxxxxxxx> wrote: >>>> >>>> 2021-07-22 17:39 UTC-0700 ~ Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> >>>>> On Wed, Jul 21, 2021 at 8:38 AM Quentin Monnet <quentin@xxxxxxxxxxxxx> wrote: >>>>>> >>>>>> Rename function btf__get_from_id() as btf__load_from_kernel_by_id() to >>>>>> better indicate what the function does. Change the new function so that, >>>>>> instead of requiring a pointer to the pointer to update and returning >>>>>> with an error code, it takes a single argument (the id of the BTF >>>>>> object) and returns the corresponding pointer. This is more in line with >>>>>> the existing constructors. >>>>>> >>>>>> The other tools calling the deprecated btf__get_from_id() function will >>>>>> be updated in a future commit. >>>>>> >>>>>> References: >>>>>> >>>>>> - https://github.com/libbpf/libbpf/issues/278 >>>>>> - https://github.com/libbpf/libbpf/wiki/Libbpf:-the-road-to-v1.0#btfh-apis >>>>>> >> >>>>>> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c >>>>>> index 7e0de560490e..6654bdee7ad7 100644 >>>>>> --- a/tools/lib/bpf/btf.c >>>>>> +++ b/tools/lib/bpf/btf.c >>>>>> @@ -1383,21 +1383,30 @@ struct btf *btf_get_from_fd(int btf_fd, struct btf *base_btf) >>>>>> return btf; >>>>>> } >>>>>> >>>>>> +struct btf *btf__load_from_kernel_by_id(__u32 id) >>>>>> +{ >>>>>> + struct btf *btf; >>>>>> + int btf_fd; >>>>>> + >>>>>> + btf_fd = bpf_btf_get_fd_by_id(id); >>>>>> + if (btf_fd < 0) >>>>>> + return ERR_PTR(-errno); >>>>> >>>>> please use libbpf_err_ptr() for consistency, see >>>>> bpf_object__open_mem() for an example >>>> >>>> I can do that, but I'll need to uncouple btf__get_from_id() from the new >>>> function. If it calls btf__load_from_kernel_by_id() and >>>> LIBBPF_STRICT_CLEAN_PTRS is set, it would change its return value. >>> >>> No it won't, if libbpf_get_error() is used right after the API call. >> >> But we cannot be sure that users currently call libbpf_get_error() after >> btf__get_from_id()? I'm fine if we assume they do (users currently >> selecting the CLEAN_PTRS are probably savvy enough to call it I guess), >> I'll update as you suggest. > > I think you are still confused. OK, I think I was. I'm not arguing against the contract, but I thought your suggestion would introduce a change in btf__get_from_id()'s behaviour. Reading again through the code and your explanations, there should be no change indeed, I just misunderstood in the first place. Apologies, and thanks for your patience :). I'll prepare v3 soon. Quentin
