bpftool: Use a local copy of BPF_LINK_TYPE_PERF_EVENT in pid_iter.bpf.c

In order to allow the BPF program in bpftool's pid_iter.bpf.c to compile correctly on hosts where vmlinux.h does not define BPF_LINK_TYPE_PERF_EVENT (running kernel versions lower than 5.15, for example), define and use a local copy of the enum value. This requires LLVM 12 or newer to build the BPF program. Fixes: cbdaf71f7e65 ("bpftool: Add bpf_cookie to link output") Signed-off-by: Quentin Monnet <[email protected]> Signed-off-by: Andrii Nakryiko <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
libbpf · Jul 12, 2023 · fc96090 · fc96090
1 parent 0773871
commit fc96090
Showing 1 changed file with 9 additions and 2 deletions.
diff --git a/src/skeleton/pid_iter.bpf.c b/src/skeleton/pid_iter.bpf.c
@@ -24,6 +24,10 @@ struct perf_event___local {
 	u64 bpf_cookie;
 } __attribute__((preserve_access_index));
 
+enum bpf_link_type___local {
+	BPF_LINK_TYPE_PERF_EVENT___local = 7,
+};
+
 extern const void bpf_link_fops __ksym;
 extern const void bpf_map_fops __ksym;
 extern const void bpf_prog_fops __ksym;
@@ -93,10 +97,13 @@ int iter(struct bpf_iter__task_file *ctx)
 	e.pid = task->tgid;
 	e.id = get_obj_id(file->private_data, obj_type);
 
-	if (obj_type == BPF_OBJ_LINK) {
+	if (obj_type == BPF_OBJ_LINK &&
+	    bpf_core_enum_value_exists(enum bpf_link_type___local,
+				       BPF_LINK_TYPE_PERF_EVENT___local)) {
 		struct bpf_link *link = (struct bpf_link *) file->private_data;
 
-		if (BPF_CORE_READ(link, type) == BPF_LINK_TYPE_PERF_EVENT) {
+		if (link->type == bpf_core_enum_value(enum bpf_link_type___local,
+						      BPF_LINK_TYPE_PERF_EVENT___local)) {
 			e.has_bpf_cookie = true;
 			e.bpf_cookie = get_bpf_cookie(link);
 		}