perf probe: Fix error message if get_real_path() failed

Perf probe -L shows incorrect error message (Dwarf error) if it fails to find
source file. This can confuse users.

# ./perf probe -s /nowhere -L vfs_read
Debuginfo analysis failed. (-2)
  Error: Failed to show lines. (-2)

With this patch, it shows correct message.

# ./perf probe -s /nowhere -L vfs_read
Failed to find source file. (-2)
  Error: Failed to show lines. (-2)

LKML-Reference: <4C36EBDB.4020308@hitachi.com>
Cc: Chase Douglas <chase.douglas@canonical.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: Chase Douglas <chase.douglas@canonical.com>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 59 insertions, 0 deletions

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 09cf5465e10a..8d08e75b2dd3 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -195,6 +195,55 @@ static int try_to_find_kprobe_trace_events(struct perf_probe_event *pev,
         return ntevs;
 }
 
+/*
+ * Find a src file from a DWARF tag path. Prepend optional source path prefix
+ * and chop off leading directories that do not exist. Result is passed back as
+ * a newly allocated path on success.
+ * Return 0 if file was found and readable, -errno otherwise.
+ */
+static int get_real_path(const char *raw_path, char **new_path)
+{
+        if (!symbol_conf.source_prefix) {
+                if (access(raw_path, R_OK) == 0) {
+                        *new_path = strdup(raw_path);
+                        return 0;
+                } else
+                        return -errno;
+        }
+
+        *new_path = malloc((strlen(symbol_conf.source_prefix) +
+                            strlen(raw_path) + 2));
+        if (!*new_path)
+                return -ENOMEM;
+
+        for (;;) {
+                sprintf(*new_path, "%s/%s", symbol_conf.source_prefix,
+                        raw_path);
+
+                if (access(*new_path, R_OK) == 0)
+                        return 0;
+
+                switch (errno) {
+                case ENAMETOOLONG:
+                case ENOENT:
+                case EROFS:
+                case EFAULT:
+                        raw_path = strchr(++raw_path, '/');
+                        if (!raw_path) {
+                                free(*new_path);
+                                *new_path = NULL;
+                                return -ENOENT;
+                        }
+                        continue;
+
+                default:
+                        free(*new_path);
+                        *new_path = NULL;
+                        return -errno;
+                }
+        }
+}
+
 #define LINEBUF_SIZE 256
 #define NR_ADDITIONAL_LINES 2
 
@@ -244,6 +293,7 @@ int show_line_range(struct line_range *lr)
         struct line_node *ln;
         FILE *fp;
         int fd, ret;
+        char *tmp;
 
         /* Search a line range */
         ret = init_vmlinux();
@@ -266,6 +316,15 @@ int show_line_range(struct line_range *lr)
                 return ret;
         }
 
+        /* Convert source file path */
+        tmp = lr->path;
+        ret = get_real_path(tmp, &lr->path);
+        free(tmp);      /* Free old path */
+        if (ret < 0) {
+                pr_warning("Failed to find source file. (%d)\n", ret);
+                return ret;
+        }
+
         setup_pager();
 
         if (lr->function)