[PATCH -tip v2 9/9] [BUGFIX] perf probe: Filter out redundant inline-instances

Masami Hiramatsu
2011-08-11T11:27:31Z

With gcc4.6, some instances of concrete inlined function
looks redundant and broken, because it appears inside of a
concrete instance and its call_file and call_line are same
as the original abstruct's decl_file and decl_line respectively.

e.g.
[ d1aa] subprogram
external (flag) Yes
name (strp) "add_timer"
decl_file (data1) 2 ;here is original
decl_line (data2) 847 ;line and file
prototyped (flag) Yes
inline (data1) inlined (1)
sibling (ref4) [ d1c6]
...
[ 11d84] subprogram
abstract_origin (ref4) [ d1aa] ; concrete instance
low_pc (addr) .text+0x000000000000246f <add_timer>
high_pc (addr) .text+0x000000000000248b <mod_timer_pending>
frame_base (block1) [ 0] call_frame_cfa
sibling (ref4) [ 11dd9]
[ 11d9f] formal_parameter
abstract_origin (ref4) [ d1b9]
location (data4) location list [ 701b]
[ 11da8] inlined_subroutine
abstract_origin (ref4) [ d1aa] ; redundant instance
low_pc (addr) .text+0x000000000000247e <add_timer+0xf>
high_pc (addr) .text+0x0000000000002480 <add_timer+0x11>
call_file (data1) 2 ; call line and file
call_line (data2) 847 ; are same as above

Those redundant instances leads unwilling results;

e.g. find probe points inside of functions even if we specify
a function entry as below;

$ perf probe -V add_timer
Available variables at add_timer
@<add_timer+0>
struct timer_list* timer
@<add_timer+15>
(No matched variables)

So, this filters out those redundant instances based on
call-site and decl-site information.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
---

tools/perf/util/dwarf-aux.c | 22 ++++++++++++++++++++++
1 files changed, 22 insertions(+), 0 deletions(-)

diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index d0f4048..ee51e9b 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -307,6 +307,17 @@ static int die_get_call_fileno(Dwarf_Die *in_die)
return -ENOENT;
}

+/* Get the declared file index number in CU DIE */
+static int die_get_decl_fileno(Dwarf_Die *pdie)
+{
+ Dwarf_Sword idx;
+
+ if (die_get_attr_sdata(pdie, DW_AT_decl_file, &idx) == 0)
+ return (int)idx;
+ else
+ return -ENOENT;
+}
+
/**
* die_get_call_file - Get callsite file name of inlined function instance
* @in_die: a DIE of an inlined function instance
@@ -467,6 +478,7 @@ static int __die_walk_instances_cb(Dwarf_Die *inst, void *data)
Dwarf_Die origin_mem;
Dwarf_Attribute *attr;
Dwarf_Die *origin;
+ int tmp;

attr = dwarf_attr(inst, DW_AT_abstract_origin, &attr_mem);
if (attr == NULL)
@@ -476,6 +488,16 @@ static int __die_walk_instances_cb(Dwarf_Die *inst, void *data)
if (origin == NULL || origin->addr != iwp->addr)
return DIE_FIND_CB_CONTINUE;

+ /* Ignore redundant instances */
+ if (dwarf_tag(inst) == DW_TAG_inlined_subroutine) {
+ dwarf_decl_line(origin, &tmp);
+ if (die_get_call_lineno(inst) == tmp) {
+ tmp = die_get_decl_fileno(origin);
+ if (die_get_call_fileno(inst) == tmp)
+ return DIE_FIND_CB_CONTINUE;
+ }
+ }
+
iwp->retval = iwp->callback(inst, iwp->data);

return (iwp->retval) ? DIE_FIND_CB_END : DIE_FIND_CB_CONTINUE;