perf/probes: Improve error messages

Improve error messages in perf-probe so that users can figure
out problems easily.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Frank Ch. Eigler <fche@redhat.com>
Cc: Jason Baron <jbaron@redhat.com>
Cc: K.Prasad <prasad@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
LKML-Reference: <20091104001221.3454.52030.stgit@harusame>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 13 insertions, 7 deletions

diff --git a/tools/perf/builtin-probe.c b/tools/perf/builtin-probe.c
index 81245238e341..65bcaed0ef49 100644
--- a/tools/perf/builtin-probe.c
+++ b/tools/perf/builtin-probe.c
@@ -294,10 +294,11 @@ static int write_new_event(int fd, const char *buf)
 {
         int ret;
 
-        printf("Adding new event: %s\n", buf);
         ret = write(fd, buf, strlen(buf));
         if (ret <= 0)
-                die("failed to create event.");
+                die("Failed to create event.");
+        else
+                printf("Added new event: %s\n", buf);
 
         return ret;
 }
@@ -310,7 +311,7 @@ static int synthesize_probe_event(struct probe_point *pp)
         int i, len, ret;
         pp->probes[0] = buf = (char *)calloc(MAX_CMDLEN, sizeof(char));
         if (!buf)
-                die("calloc");
+                die("Failed to allocate memory by calloc.");
         ret = snprintf(buf, MAX_CMDLEN, "%s+%d", pp->function, pp->offset);
         if (ret <= 0 || ret >= MAX_CMDLEN)
                 goto error;
@@ -363,7 +364,7 @@ int cmd_probe(int argc, const char **argv, const char *prefix __used)
                 if (ret == -E2BIG)
                         semantic_error("probe point is too long.");
                 else if (ret < 0)
-                        die("snprintf");
+                        die("Failed to synthesize a probe point.");
         }
 
 #ifndef NO_LIBDWARF
@@ -375,7 +376,7 @@ int cmd_probe(int argc, const char **argv, const char *prefix __used)
         else
                 fd = open_default_vmlinux();
         if (fd < 0)
-                die("vmlinux/module file open");
+                die("Could not open vmlinux/module file.");
 
         /* Searching probe points */
         for (j = 0; j < session.nr_probe; j++) {
@@ -396,8 +397,13 @@ setup_probes:
         /* Settng up probe points */
         snprintf(buf, MAX_CMDLEN, "%s/../kprobe_events", debugfs_path);
         fd = open(buf, O_WRONLY, O_APPEND);
-        if (fd < 0)
-                die("kprobe_events open");
+        if (fd < 0) {
+                if (errno == ENOENT)
+                        die("kprobe_events file does not exist - please rebuild with CONFIG_KPROBE_TRACER.");
+                else
+                        die("Could not open kprobe_events file: %s",
+                            strerror(errno));
+        }
         for (j = 0; j < session.nr_probe; j++) {
                 pp = &session.probes[j];
                 if (pp->found == 1) {