perf probe: Fix perf probe to find correct variable DIE

Fix perf probe to find correct variable DIE which has location or
external instance by tracking down the lexical blocks.

Current die_find_variable() expects that the all variable DIEs
which has DW_TAG_variable have a location. However, since recent
dwarf information may have declaration variable DIEs at the
entry of function (subprogram), die_find_variable() returns it.

To solve this problem, it must track down the DIE tree to find
a DIE which has an actual location or a reference for external
instance.

e.g. finding a DIE which origin is <0xdc73>;

 <1><11496>: Abbrev Number: 95 (DW_TAG_subprogram)
    <11497>   DW_AT_abstract_origin: <0xdc42>
    <1149b>   DW_AT_low_pc      : 0x1850
[...]
 <2><114cc>: Abbrev Number: 119 (DW_TAG_variable) <- this is a declaration
    <114cd>   DW_AT_abstract_origin: <0xdc73>
 <2><114d1>: Abbrev Number: 119 (DW_TAG_variable)
[...]
 <3><115a7>: Abbrev Number: 105 (DW_TAG_lexical_block)
    <115a8>   DW_AT_ranges      : 0xaa0
 <4><115ac>: Abbrev Number: 96 (DW_TAG_variable) <- this has a location
    <115ad>   DW_AT_abstract_origin: <0xdc73>
    <115b1>   DW_AT_location    : 0x486c        (location list)

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Tested-by: Arnaldo Carvalho de Melo <acme@kernel.org>
Acked-by: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20140529121930.30879.87092.stgit@ltc230.yrl.intra.hitachi.co.jp
Signed-off-by: Jiri Olsa <jolsa@kernel.org>

diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index 7defd77105d005f9820c7ca69621e814a3c45c76..cc66c4049e0921ea35910edcebffb89b525c2f57 100644 (file)
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -747,14 +747,17 @@ struct __find_variable_param {
 static int __die_find_variable_cb(Dwarf_Die *die_mem, void *data)
 {
        struct __find_variable_param *fvp = data;
+       Dwarf_Attribute attr;
        int tag;
 
        tag = dwarf_tag(die_mem);
        if ((tag == DW_TAG_formal_parameter ||
             tag == DW_TAG_variable) &&
-           die_compare_name(die_mem, fvp->name))
+           die_compare_name(die_mem, fvp->name) &&
+       /* Does the DIE have location information or external instance? */
+           (dwarf_attr(die_mem, DW_AT_external, &attr) ||
+            dwarf_attr(die_mem, DW_AT_location, &attr)))
                return DIE_FIND_CB_END;
-
        if (dwarf_haspc(die_mem, fvp->addr))
                return DIE_FIND_CB_CONTINUE;
        else