netdev - [PATCH bpf-next] libbpf: making bpf_prog_load() ignore name if kernel doesn't support

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Message-Id: <20220812024038.7056-1-liuhangbin@gmail.com>
Date:   Fri, 12 Aug 2022 10:40:38 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     netdev@...r.kernel.org
Cc:     Quentin Monnet <quentin@...valent.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        bpf@...r.kernel.org, Hangbin Liu <liuhangbin@...il.com>
Subject: [PATCH bpf-next] libbpf: making bpf_prog_load() ignore name if kernel doesn't support

Similar with commit 10b62d6a38f7 ("libbpf: Add names for auxiliary maps"),
let's make bpf_prog_load() also ignore name if kernel doesn't support
program name.

To achieve this, we need to call sys_bpf_prog_load() directly in
probe_kern_prog_name() to avoid circular dependency. sys_bpf_prog_load()
also need to be exported in the bpf.h file.

Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
---
 tools/lib/bpf/bpf.c    |  6 ++----
 tools/lib/bpf/bpf.h    |  3 +++
 tools/lib/bpf/libbpf.c | 11 +++++++++--
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 6a96e665dc5d..575867d69496 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -84,9 +84,7 @@ static inline int sys_bpf_fd(enum bpf_cmd cmd, union bpf_attr *attr,
 	return ensure_good_fd(fd);
 }
 
-#define PROG_LOAD_ATTEMPTS 5
-
-static inline int sys_bpf_prog_load(union bpf_attr *attr, unsigned int size, int attempts)
+int sys_bpf_prog_load(union bpf_attr *attr, unsigned int size, int attempts)
 {
 	int fd;
 
@@ -263,7 +261,7 @@ int bpf_prog_load(enum bpf_prog_type prog_type,
 	attr.prog_ifindex = OPTS_GET(opts, prog_ifindex, 0);
 	attr.kern_version = OPTS_GET(opts, kern_version, 0);
 
-	if (prog_name)
+	if (prog_name && kernel_supports(NULL, FEAT_PROG_NAME))
 		libbpf_strlcpy(attr.prog_name, prog_name, sizeof(attr.prog_name));
 	attr.license = ptr_to_u64(license);
 
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 9c50beabdd14..125c580e45f8 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -35,6 +35,9 @@
 extern "C" {
 #endif
 
+#define PROG_LOAD_ATTEMPTS 5
+int sys_bpf_prog_load(union bpf_attr *attr, unsigned int size, int attempts);
+
 int libbpf_set_memlock_rlim(size_t memlock_bytes);
 
 struct bpf_map_create_opts {
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 3f01f5cd8a4c..1bcb2735d3f1 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4419,10 +4419,17 @@ static int probe_kern_prog_name(void)
 		BPF_MOV64_IMM(BPF_REG_0, 0),
 		BPF_EXIT_INSN(),
 	};
-	int ret, insn_cnt = ARRAY_SIZE(insns);
+	union bpf_attr attr = {
+		.prog_type = BPF_PROG_TYPE_SOCKET_FILTER,
+		.prog_name = "test",
+		.license = ptr_to_u64("GPL"),
+		.insns = ptr_to_u64(insns),
+		.insn_cnt = (__u32)ARRAY_SIZE(insns),
+	};
+	int ret;
 
 	/* make sure loading with name works */
-	ret = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, "test", "GPL", insns, insn_cnt, NULL);
+	ret = sys_bpf_prog_load(&attr, sizeof(attr), PROG_LOAD_ATTEMPTS);
 	return probe_fd(ret);
 }
 
-- 
2.31.1