Merge branch 'Enhance and rework logging controls in libbpf'

Andrii Nakryiko says:

====================

Add new open options and per-program setters to control BTF and program
loading log verboseness and allow providing custom log buffers to capture logs
of interest. Note how custom log_buf and log_level are orthogonal, which
matches previous (alas less customizable) behavior of libbpf, even though it
sort of worked by accident: if someone specified log_level = 1 in
bpf_object__load_xattr(), first attempt to load any BPF program resulted in
wasted bpf() syscall with -EINVAL due to !!log_buf != !!log_level. Then on
retry libbpf would allocated log_buffer and try again, after which prog
loading would succeed and libbpf would print verbose program loading log
through its print callback.

This behavior is now documented and made more efficient, not wasting
unnecessary syscall. But additionally, log_level can be controlled globally on
a per-bpf_object level through bpf_object_open_opts, as well as on
a per-program basis with bpf_program__set_log_buf() and
bpf_program__set_log_level() APIs.

Now that we have a more future-proof way to set log_level, deprecate
bpf_object__load_xattr().

v2->v3:
  - added log_buf selftests for bpf_prog_load() and bpf_btf_load();
  - fix !log_buf in bpf_prog_load (John);
  - fix log_level==0 in bpf_btf_load (thanks selftest!);

v1->v2:
  - fix log_level == 0 handling of bpf_prog_load, add as patch #1 (Alexei);
  - add comments explaining log_buf_size overflow prevention (Alexei).
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

1 files changed, 4 insertions, 7 deletions

diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index 997a2865e04a..b4695df2ea3d 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -486,7 +486,6 @@ static void codegen_destroy(struct bpf_object *obj, const char *obj_name)
 
 static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *header_guard)
 {
-	struct bpf_object_load_attr load_attr = {};
 	DECLARE_LIBBPF_OPTS(gen_loader_opts, opts);
 	struct bpf_map *map;
 	char ident[256];
@@ -496,12 +495,7 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h
 	if (err)
 		return err;
 
-	load_attr.obj = obj;
-	if (verifier_logs)
-		/* log_level1 + log_level2 + stats, but not stable UAPI */
-		load_attr.log_level = 1 + 2 + 4;
-
-	err = bpf_object__load_xattr(&load_attr);
+	err = bpf_object__load(obj);
 	if (err) {
 		p_err("failed to load object file");
 		goto out;
@@ -719,6 +713,9 @@ static int do_skeleton(int argc, char **argv)
 	if (obj_name[0] == '\0')
 		get_obj_name(obj_name, file);
 	opts.object_name = obj_name;
+	if (verifier_logs)
+		/* log_level1 + log_level2 + stats, but not stable UAPI */
+		opts.kernel_log_level = 1 + 2 + 4;
 	obj = bpf_object__open_mem(obj_data, file_sz, &opts);
 	err = libbpf_get_error(obj);
 	if (err) {