On 10/7/19 4:41 PM, Andrii Nakryiko wrote:
> 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?
make sense.
>> 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?
128 is ksym_name and due to tp construction with other prefixes,
I think, it cannot overflow, but that's a good nit. Fixed it.
