linux-kernel - [PATCH 2/5] tools lib bpf: Report error when kernel doesn't support program type

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Message-ID: <1468406646-21642-3-git-send-email-wangnan0@huawei.com>
Date:	Wed, 13 Jul 2016 10:44:02 +0000
From:	Wang Nan <wangnan0@...wei.com>
To:	<acme@...nel.org>
CC:	<lizefan@...wei.com>, <linux-kernel@...r.kernel.org>,
	<pi3orama@....com>, Wang Nan <wangnan0@...wei.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Jiri Olsa <jolsa@...nel.org>
Subject: [PATCH 2/5] tools lib bpf: Report error when kernel doesn't support program type

Now libbpf support tracepoint program type. Report meanful error when
kernel version less than 4.7.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Li Zefan <lizefan@...wei.com>
Cc: Jiri Olsa <jolsa@...nel.org>
---
 tools/lib/bpf/libbpf.c | 27 ++++++++++++++++++++-------
 tools/lib/bpf/libbpf.h |  1 +
 2 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 4751936..32e6b6b 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -90,6 +90,7 @@ static const char *libbpf_strerror_table[NR_ERRNO] = {
 	[ERRCODE_OFFSET(VERIFY)]	= "Kernel verifier blocks program loading",
 	[ERRCODE_OFFSET(PROG2BIG)]	= "Program too big",
 	[ERRCODE_OFFSET(KVER)]		= "Incorrect kernel version",
+	[ERRCODE_OFFSET(PROGTYPE)]	= "Kernel doesn't support this program type",
 };
 
 int libbpf_strerror(int err, char *buf, size_t size)
@@ -926,15 +927,27 @@ load_program(enum bpf_prog_type type, struct bpf_insn *insns,
 		pr_warning("-- BEGIN DUMP LOG ---\n");
 		pr_warning("\n%s\n", log_buf);
 		pr_warning("-- END LOG --\n");
+	} else if (insns_cnt >= BPF_MAXINSNS) {
+		pr_warning("Program too large (%d insns), at most %d insns\n",
+			   insns_cnt, BPF_MAXINSNS);
+		ret = -LIBBPF_ERRNO__PROG2BIG;
 	} else {
-		if (insns_cnt >= BPF_MAXINSNS) {
-			pr_warning("Program too large (%d insns), at most %d insns\n",
-				   insns_cnt, BPF_MAXINSNS);
-			ret = -LIBBPF_ERRNO__PROG2BIG;
-		} else if (log_buf) {
-			pr_warning("log buffer is empty\n");
-			ret = -LIBBPF_ERRNO__KVER;
+		/* Wrong program type? */
+		if (type != BPF_PROG_TYPE_KPROBE) {
+			int fd;
+
+			fd = bpf_load_program(BPF_PROG_TYPE_KPROBE, insns,
+					      insns_cnt, license, kern_version,
+					      NULL, 0);
+			if (fd >= 0) {
+				close(fd);
+				ret = -LIBBPF_ERRNO__PROGTYPE;
+				goto out;
+			}
 		}
+
+		if (log_buf)
+			ret = -LIBBPF_ERRNO__KVER;
 	}
 
 out:
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index eb2a4c4..dd7a513 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -39,6 +39,7 @@ enum libbpf_errno {
 	LIBBPF_ERRNO__VERIFY,	/* Kernel verifier blocks program loading */
 	LIBBPF_ERRNO__PROG2BIG,	/* Program too big */
 	LIBBPF_ERRNO__KVER,	/* Incorrect kernel version */
+	LIBBPF_ERRNO__PROGTYPE,	/* Kernel doesn't support this program type */
 	__LIBBPF_ERRNO__END,
 };
 
-- 
1.8.3.4