tools lib bpf: Report error when kernel doesn't support program type

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

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1468406646-21642-3-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 21 insertions, 7 deletions

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 4751936831d7..32e6b6bc6f7d 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 eb2a4c45f6b6..dd7a513efb10 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,
 };