perf probe: Fix --list option to show events only with uprobe events

Current perf probe --list doesn't work if only CONFIG_UPROBE_EVENTS=y
because it aborts when it fails to open kprobe_events file before
checking uprobe_events file.

This fixes --list option to show dynamic events if it can open either
kprobe_events or uprobe_events. Only if it failed to open both of them,
it shows an error message and aborts.

Without this patch, if we run perf probe -l on the kernel configured
with CONFIG_KPROBE_EVENTS=n and CONFIG_UPROBE_EVENTS=y,

  # perf probe -l
  /sys/kernel/debug/tracing/kprobe_events file does not exist - please rebuild ker
    Error: Failed to show event list.

With this patch,

  # perf probe -l
    probe_perf:alloc_event (on alloc_event@lib/traceevent/event-parse.c in /home/fedora/ksrc/linux-3/tools/perf/perf)

Changes in v2:
 - Use strerror_r instead of strerror.

Reported-by: Naohiro Aota <naota@elisp.net>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Naohiro Aota <naota@elisp.net>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20140813161248.26440.84370.stgit@kbuild-fedora.novalocal
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 9a0a183..50aa7f0 100644 (file)
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -1780,10 +1780,11 @@ static void clear_probe_trace_event(struct probe_trace_event *tev)
        memset(tev, 0, sizeof(*tev));
 }
 
-static void print_warn_msg(const char *file, bool is_kprobe)
+static void print_open_warning(int err, bool is_kprobe)
 {
+       char sbuf[128];
 
-       if (errno == ENOENT) {
+       if (err == -ENOENT) {
                const char *config;
 
                if (!is_kprobe)
@@ -1791,25 +1792,26 @@ static void print_warn_msg(const char *file, bool is_kprobe)
                else
                        config = "CONFIG_KPROBE_EVENTS";
 
-               pr_warning("%s file does not exist - please rebuild kernel"
-                               " with %s.\n", file, config);
-       } else
-               pr_warning("Failed to open %s file: %s\n", file,
-                               strerror(errno));
+               pr_warning("%cprobe_events file does not exist"
+                          " - please rebuild kernel with %s.\n",
+                          is_kprobe ? 'k' : 'u', config);
+       } else if (err == -ENOTSUP)
+               pr_warning("Debugfs is not mounted.\n");
+       else
+               pr_warning("Failed to open %cprobe_events: %s\n",
+                          is_kprobe ? 'k' : 'u',
+                          strerror_r(-err, sbuf, sizeof(sbuf)));
 }
 
-static int open_probe_events(const char *trace_file, bool readwrite,
-                               bool is_kprobe)
+static int open_probe_events(const char *trace_file, bool readwrite)
 {
        char buf[PATH_MAX];
        const char *__debugfs;
        int ret;
 
        __debugfs = debugfs_find_mountpoint();
-       if (__debugfs == NULL) {
-               pr_warning("Debugfs is not mounted.\n");
-               return -ENOENT;
-       }
+       if (__debugfs == NULL)
+               return -ENOTSUP;
 
        ret = e_snprintf(buf, PATH_MAX, "%s/%s", __debugfs, trace_file);
        if (ret >= 0) {
@@ -1820,19 +1822,19 @@ static int open_probe_events(const char *trace_file, bool readwrite,
                        ret = open(buf, O_RDONLY, 0);
 
                if (ret < 0)
-                       print_warn_msg(buf, is_kprobe);
+                       ret = -errno;
        }
        return ret;
 }
 
 static int open_kprobe_events(bool readwrite)
 {
-       return open_probe_events("tracing/kprobe_events", readwrite, true);
+       return open_probe_events("tracing/kprobe_events", readwrite);
 }
 
 static int open_uprobe_events(bool readwrite)
 {
-       return open_probe_events("tracing/uprobe_events", readwrite, false);
+       return open_probe_events("tracing/uprobe_events", readwrite);
 }
 
 /* Get raw string list of current kprobe_events  or uprobe_events */
@@ -1940,27 +1942,47 @@ static int __show_perf_probe_events(int fd, bool is_kprobe)
 /* List up current perf-probe events */
 int show_perf_probe_events(void)
 {
-       int fd, ret;
+       int kp_fd, up_fd, ret;
 
        setup_pager();
-       fd = open_kprobe_events(false);
-
-       if (fd < 0)
-               return fd;
 
        ret = init_symbol_maps(false);
        if (ret < 0)
                return ret;
 
-       ret = __show_perf_probe_events(fd, true);
-       close(fd);
+       kp_fd = open_kprobe_events(false);
+       if (kp_fd >= 0) {
+               ret = __show_perf_probe_events(kp_fd, true);
+               close(kp_fd);
+               if (ret < 0)
+                       goto out;
+       }
 
-       fd = open_uprobe_events(false);
-       if (fd >= 0) {
-               ret = __show_perf_probe_events(fd, false);
-               close(fd);
+       up_fd = open_uprobe_events(false);
+       if (kp_fd < 0 && up_fd < 0) {
+               /* Both kprobes and uprobes are disabled, warn it. */
+               if (kp_fd == -ENOTSUP && up_fd == -ENOTSUP)
+                       pr_warning("Debugfs is not mounted.\n");
+               else if (kp_fd == -ENOENT && up_fd == -ENOENT)
+                       pr_warning("Please rebuild kernel with "
+                                  "CONFIG_KPROBE_EVENTS or/and "
+                                  "CONFIG_UPROBE_EVENTS.\n");
+               else {
+                       char sbuf[128];
+                       pr_warning("Failed to open kprobe events: %s.\n",
+                                  strerror_r(-kp_fd, sbuf, sizeof(sbuf)));
+                       pr_warning("Failed to open uprobe events: %s.\n",
+                                  strerror_r(-up_fd, sbuf, sizeof(sbuf)));
+               }
+               ret = kp_fd;
+               goto out;
        }
 
+       if (up_fd >= 0) {
+               ret = __show_perf_probe_events(up_fd, false);
+               close(up_fd);
+       }
+out:
        exit_symbol_maps();
        return ret;
 }
@@ -2075,8 +2097,11 @@ static int __add_probe_trace_events(struct perf_probe_event *pev,
        else
                fd = open_kprobe_events(true);
 
-       if (fd < 0)
+       if (fd < 0) {
+               print_open_warning(fd, !pev->uprobes);
                return fd;
+       }
+
        /* Get current event names */
        namelist = get_probe_trace_event_names(fd, false);
        if (!namelist) {
@@ -2449,13 +2474,17 @@ int del_perf_probe_events(struct strlist *dellist)
 
        /* Get current event names */
        kfd = open_kprobe_events(true);
-       if (kfd < 0)
+       if (kfd < 0) {
+               print_open_warning(kfd, true);
                return kfd;
+       }
 
        namelist = get_probe_trace_event_names(kfd, true);
        ufd = open_uprobe_events(true);
 
-       if (ufd >= 0)
+       if (ufd < 0)
+               print_open_warning(ufd, false);
+       else
                unamelist = get_probe_trace_event_names(ufd, true);
 
        if (namelist == NULL && unamelist == NULL)