[PATCH bpf-next 03/11] tools, bpf: fix bpftool build with !CONFIG_BPF_EVENTS

[Alexander Lobakin <alobakin@pm.me>]

Fix the following error when building bpftool:

  CLANG   profiler.bpf.o
  CLANG   pid_iter.bpf.o
skeleton/profiler.bpf.c:18:21: error: invalid application of 'sizeof' to an incomplete type 'struct bpf_perf_event_value'
        __uint(value_size, sizeof(struct bpf_perf_event_value));
                           ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_helpers.h:13:39: note: expanded from macro '__uint'
                                      ^~~
tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_helper_defs.h:7:8: note: forward declaration of 'struct bpf_perf_event_value'
struct bpf_perf_event_value;
       ^

struct bpf_perf_event_value is being used in the kernel only when
CONFIG_BPF_EVENTS is enabled, so it misses a BTF entry then.
Emit the type unconditionally to fix the problem.

Fixes: 47c09d6a9f67 ("bpftool: Introduce "prog profile" command")
Signed-off-by: Alexander Lobakin <alobakin@pm.me>
---
 kernel/bpf/syscall.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 34fdf27d14cf..dd8284a60a8e 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -4286,6 +4286,7 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr)
 		goto out;
 	case BPF_PROG_TYPE_PERF_EVENT:
 	case BPF_PROG_TYPE_TRACEPOINT:
+		BTF_TYPE_EMIT(struct bpf_perf_event_value);
 		if (attr->link_create.attach_type != BPF_PERF_EVENT) {
 			ret = -EINVAL;
 			goto out;
--
2.35.2