On Fri, Oct 4, 2019 at 10:04 PM Alexei Starovoitov <ast@xxxxxxxxxx> wrote:
>
> For raw tracepoint program types libbpf will try to find
> btf_id of raw tracepoint in vmlinux's BTF.
> It's a responsiblity of bpf program author to annotate the program
> with SEC("raw_tracepoint/name") where "name" is a valid raw tracepoint.
As an aside, I've been thinking about allowing to specify "raw_tp/"
and "tp/" in section name as an "alias" for "raw_tracepoint/" and
"tracepoint/", respectively. Any objections?
> If "name" is indeed a valid raw tracepoint then in-kernel BTF
> will have "btf_trace_##name" typedef that points to function
> prototype of that raw tracepoint. BTF description captures
> exact argument the kernel C code is passing into raw tracepoint.
> The kernel verifier will check the types while loading bpf program.
>
> Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
> ---
> tools/lib/bpf/libbpf.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index e0276520171b..0e6f7b41c521 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -4591,6 +4591,22 @@ int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
> continue;
> *prog_type = section_names[i].prog_type;
> *expected_attach_type = section_names[i].expected_attach_type;
> + if (*prog_type == BPF_PROG_TYPE_RAW_TRACEPOINT) {
> + struct btf *btf = bpf_core_find_kernel_btf();
> + char raw_tp_btf_name[128] = "btf_trace_";
> + int ret;
> +
> + if (IS_ERR(btf))
> + /* lack of kernel BTF is not a failure */
> + return 0;
> + /* append "btf_trace_" prefix per kernel convention */
> + strcpy(raw_tp_btf_name + sizeof("btf_trace_") - 1,
> + name + section_names[i].len);
buffer overflow here? use strncat() instead?
> + ret = btf__find_by_name(btf, raw_tp_btf_name);
> + if (ret > 0)
> + *expected_attach_type = ret;
> + btf__free(btf);
> + }
> return 0;
> }
> pr_warning("failed to guess program type based on ELF section name '%s'\n", name);
> --
> 2.20.0
>
