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Subject[PATCH 2/5] tools lib bpf: Report error when kernel doesn't support program type
Date
Now libbpf support tracepoint program type. Report meanful error when
kernel version less than 4.7.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.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
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