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Message-Id: <20190121072515.16522-1-treeze.taeung@gmail.com>
Date:   Mon, 21 Jan 2019 16:25:15 +0900
From:   Taeung Song <treeze.taeung@...il.com>
To:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>
Cc:     netdev@...r.kernel.org,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Quentin Monnet <quentin.monnet@...ronome.com>,
        Andrey Ignatov <rdna@...com>
Subject: [PATCH RESEND bpf-next v3] libbpf: Show supported ELF section names on when failed to guess a prog/attach type

We need to let users check their wrong ELF section name
with proper ELF section names when failed to get a prog/attach type from it.
Because users can't realize libbpf guess prog/attach types from
given ELF section names.
For example, when a 'cgroup' section name of a BPF program is used,
show available ELF section names(types).

Before:

    $ bpftool prog load bpf-prog.o /sys/fs/bpf/prog1
    Error: failed to guess program type based on ELF section name cgroup

After:

    libbpf: failed to guess program type based on ELF section name 'cgroup'
    libbpf: supported section(type) names are: socket kprobe/ kretprobe/ classifier action tracepoint/ raw_tracepoint/ xdp perf_event lwt_in lwt_out lwt_xmit lwt_seg6local cgroup_skb/ingress cgroup_skb/egress cgroup/skb cgroup/sock cgroup/post_bind4 cgroup/post_bind6 cgroup/dev sockops sk_skb/stream_parser sk_skb/stream_verdict sk_skb sk_msg lirc_mode2 flow_dissector cgroup/bind4 cgroup/bind6 cgroup/connect4 cgroup/connect6 cgroup/sendmsg4 cgroup/sendmsg6

Reviewed-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@...ronome.com>
Cc: Andrey Ignatov <rdna@...com>
Signed-off-by: Taeung Song <treeze.taeung@...il.com>
---
 tools/bpf/bpftool/prog.c                      | 10 ++----
 tools/lib/bpf/libbpf.c                        | 34 +++++++++++++++++--
 .../selftests/bpf/test_socket_cookie.c        |  4 +--
 3 files changed, 36 insertions(+), 12 deletions(-)

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index 2d1bb7d6ff51..0640e9bc0ada 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -930,10 +930,9 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
 			err = libbpf_prog_type_by_name(type, &attr.prog_type,
 						       &expected_attach_type);
 			free(type);
-			if (err < 0) {
-				p_err("unknown program type '%s'", *argv);
+			if (err < 0)
 				goto err_free_reuse_maps;
-			}
+
 			NEXT_ARG();
 		} else if (is_prefix(*argv, "map")) {
 			void *new_map_replace;
@@ -1028,11 +1027,8 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
 
 			err = libbpf_prog_type_by_name(sec_name, &prog_type,
 						       &expected_attach_type);
-			if (err < 0) {
-				p_err("failed to guess program type based on section name %s\n",
-				      sec_name);
+			if (err < 0)
 				goto err_close_obj;
-			}
 		}
 
 		bpf_program__set_ifindex(pos, ifindex);
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 169e347c76f6..ea44d7a05149 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2667,10 +2667,31 @@ static const struct {
 #undef BPF_EAPROG_SEC
 #undef BPF_APROG_COMPAT
 
+#define MAX_TYPE_NAME_SIZE 32
+
+static char *libbpf_get_type_names(bool attach_type)
+{
+	int i, len = ARRAY_SIZE(section_names) * MAX_TYPE_NAME_SIZE;
+	char *buf = malloc(len);
+
+	buf[0] = '\0';
+       /* Forge string buf with all available names */
+       for (i = 0; i < ARRAY_SIZE(section_names); i++) {
+	       if (attach_type && !section_names[i].is_attachable)
+		       continue;
+
+               strcat(buf, " ");
+               strcat(buf, section_names[i].sec);
+       }
+
+       return buf;
+}
+
 int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
 			     enum bpf_attach_type *expected_attach_type)
 {
 	int i;
+	char *type_names;
 
 	if (!name)
 		return -EINVAL;
@@ -2682,6 +2703,11 @@ int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
 		*expected_attach_type = section_names[i].expected_attach_type;
 		return 0;
 	}
+	pr_warning("failed to guess program type based on ELF section name '%s'\n", name);
+	type_names = libbpf_get_type_names(false);
+	pr_info("supported section(type) names are:%s\n", type_names);
+	free(type_names);
+
 	return -EINVAL;
 }
 
@@ -2689,6 +2715,7 @@ int libbpf_attach_type_by_name(const char *name,
 			       enum bpf_attach_type *attach_type)
 {
 	int i;
+	char *type_names;
 
 	if (!name)
 		return -EINVAL;
@@ -2701,6 +2728,11 @@ int libbpf_attach_type_by_name(const char *name,
 		*attach_type = section_names[i].attach_type;
 		return 0;
 	}
+	pr_warning("failed to guess attach type based on ELF section name '%s'\n", name);
+	type_names = libbpf_get_type_names(true);
+	pr_info("attachable section(type) names are:%s\n", type_names);
+	free(type_names);
+
 	return -EINVAL;
 }
 
@@ -2907,8 +2939,6 @@ int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
 			err = bpf_program__identify_section(prog, &prog_type,
 							    &expected_attach_type);
 			if (err < 0) {
-				pr_warning("failed to guess program type based on section name %s\n",
-					   prog->section_name);
 				bpf_object__close(obj);
 				return -EINVAL;
 			}
diff --git a/tools/testing/selftests/bpf/test_socket_cookie.c b/tools/testing/selftests/bpf/test_socket_cookie.c
index fc7832ee566b..e51d63786ff8 100644
--- a/tools/testing/selftests/bpf/test_socket_cookie.c
+++ b/tools/testing/selftests/bpf/test_socket_cookie.c
@@ -158,10 +158,8 @@ static int run_test(int cgfd)
 	bpf_object__for_each_program(prog, pobj) {
 		prog_name = bpf_program__title(prog, /*needs_copy*/ false);
 
-		if (libbpf_attach_type_by_name(prog_name, &attach_type)) {
-			log_err("Unexpected prog: %s", prog_name);
+		if (libbpf_attach_type_by_name(prog_name, &attach_type))
 			goto err;
-		}
 
 		err = bpf_prog_attach(bpf_program__fd(prog), cgfd, attach_type,
 				      BPF_F_ALLOW_OVERRIDE);
-- 
2.17.1

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