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.
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.
libbpf keeps BTF type id in expected_attach_type, but since
kernel ignores this attribute for tracing programs copy it
into attach_btf_id attribute before loading.
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
---
tools/lib/bpf/bpf.c | 3 +++
tools/lib/bpf/libbpf.c | 17 +++++++++++++++++
2 files changed, 20 insertions(+)
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index cbb933532981..79046067720f 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -228,6 +228,9 @@ int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr,
memset(&attr, 0, sizeof(attr));
attr.prog_type = load_attr->prog_type;
attr.expected_attach_type = load_attr->expected_attach_type;
+ if (attr.prog_type == BPF_PROG_TYPE_RAW_TRACEPOINT)
+ /* expected_attach_type is ignored for tracing progs */
+ attr.attach_btf_id = attr.expected_attach_type;
attr.insn_cnt = (__u32)load_attr->insns_cnt;
attr.insns = ptr_to_u64(load_attr->insns);
attr.license = ptr_to_u64(load_attr->license);
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index a02cdedc4e3f..8bf30a67428c 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4586,6 +4586,23 @@ 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_";
+ char *dst = raw_tp_btf_name + sizeof("btf_trace_") - 1;
+ int ret;
+
+ if (IS_ERR(btf))
+ /* lack of kernel BTF is not a failure */
+ return 0;
+ /* prepend "btf_trace_" prefix per kernel convention */
+ strncat(dst, name + section_names[i].len,
+ sizeof(raw_tp_btf_name) - (dst - raw_tp_btf_name));
+ 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);
--
2.23.0
