From: He Kuang <[email protected]>

Indicate to check variable location range in error message when we got
failed to find the variable.

Before this patch:

  $ perf probe --add 'generic_perform_write+118 bytes'
  Failed to find the location of bytes at this address.
   Perhaps, it has been optimized out.
    Error: Failed to add events.

After this patch:

  $ perf probe --add 'generic_perform_write+118 bytes'
  Failed to find the location of the 'bytes' variable at this address.
   Perhaps it has been optimized out.
   Use -V with the --range option to show 'bytes' location range.
    Error: Failed to add events.

Signed-off-by: He Kuang <[email protected]>
Acked-by: Masami Hiramatsu <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Wang Nan <[email protected]>
Link: 
http://lkml.kernel.org/r/[email protected]
[ Improve the error message based on lkml thread ]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
---
 tools/perf/util/probe-finder.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 5804086425aa..590a24a7f555 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -527,10 +527,12 @@ static int convert_variable(Dwarf_Die *vr_die, struct 
probe_finder *pf)
 
        ret = convert_variable_location(vr_die, pf->addr, pf->fb_ops,
                                        &pf->sp_die, pf->tvar);
-       if (ret == -ENOENT || ret == -EINVAL)
-               pr_err("Failed to find the location of %s at this address.\n"
-                      " Perhaps, it has been optimized out.\n", pf->pvar->var);
-       else if (ret == -ENOTSUP)
+       if (ret == -ENOENT || ret == -EINVAL) {
+               pr_err("Failed to find the location of the '%s' variable at 
this address.\n"
+                      " Perhaps it has been optimized out.\n"
+                      " Use -V with the --range option to show '%s' location 
range.\n",
+                      pf->pvar->var, pf->pvar->var);
+       } else if (ret == -ENOTSUP)
                pr_err("Sorry, we don't support this variable location yet.\n");
        else if (ret == 0 && pf->pvar->field) {
                ret = convert_variable_fields(vr_die, pf->pvar->var,
-- 
2.1.0

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