perf probe: Fix probing symbols with optimization suffix

Fix perf probe to probe on some symbols which have some optimzation
suffixes, e.g. ".part", ".isra", and ".constprop".

To fix this issue, instead of using the DIE name, perf probe uses the
symbol name found by dwfl_module_addrsym().

This also involves a perf probe --vars operation update which now shows
the symbol name instead of the DIE name.

Without this patch, putting a probe on an inlined function which was
compiled with a suffixed symbol will fail like this:

  $ perf probe -v getname_flags
  probe-definition(0): getname_flags
  symbol:getname_flags file:(null) line:0 offset:0 return:0 lazy:(null)
  0 arguments
  Looking at the vmlinux_path (6 entries long)
  Using /lib/modules/3.11.0+/build/vmlinux for symbols
  found inline addr: 0xffffffff8119bb70
  Probe point found: getname_flags+0
  found inline addr: 0xffffffff8119bcb6
  Probe point found: getname+6
  found inline addr: 0xffffffff811a06a6
  Probe point found: user_path_at_empty+6
  find 3 probe_trace_events.
  Opening /sys/kernel/debug//tracing/kprobe_events write=1
  Added new events:
  Writing event: p:probe/getname_flags getname_flags+0
  Failed to write event: No such file or directory
    Error: Failed to add events. (-1)

Because the debuginfo knows only the original (non suffix) symbol name,
it uses the original symbol for probe address but the kernel (kallsyms)
knows only suffixed symbol.  Then, the kernel rejects that original
symbol.

This patch uses dwfl_module_addrsym() to get the correct (suffixed)
symbol from symtab when a probe point is found.

Reported-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20130925131616.31632.46658.stgit@udc4-manage.rcp.hitachi.co.jp
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
index 17e94d0c36f9..3b7d63018960 100644
--- a/tools/perf/util/probe-finder.h
+++ b/tools/perf/util/probe-finder.h
@@ -23,6 +23,7 @@ static inline int is_c_varname(const char *name)
 /* debug information structure */
 struct debuginfo {
 	Dwarf		*dbg;
+	Dwfl_Module	*mod;
 	Dwfl		*dwfl;
 	Dwarf_Addr	bias;
 };
@@ -77,6 +78,7 @@ struct probe_finder {
 
 struct trace_event_finder {
 	struct probe_finder	pf;
+	Dwfl_Module		*mod;		/* For solving symbols */
 	struct probe_trace_event *tevs;		/* Found trace events */
 	int			ntevs;		/* Number of trace events */
 	int			max_tevs;	/* Max number of trace events */
@@ -84,6 +86,7 @@ struct trace_event_finder {
 
 struct available_var_finder {
 	struct probe_finder	pf;
+	Dwfl_Module		*mod;		/* For solving symbols */
 	struct variable_list	*vls;		/* Found variable lists */
 	int			nvls;		/* Number of variable lists */
 	int			max_vls;	/* Max no. of variable lists */