forked from luck/tmp_suning_uos_patched
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>
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@ -747,14 +747,17 @@ struct __find_variable_param {
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static int __die_find_variable_cb(Dwarf_Die *die_mem, void *data)
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{
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struct __find_variable_param *fvp = data;
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Dwarf_Attribute attr;
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int tag;
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tag = dwarf_tag(die_mem);
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if ((tag == DW_TAG_formal_parameter ||
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tag == DW_TAG_variable) &&
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die_compare_name(die_mem, fvp->name))
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die_compare_name(die_mem, fvp->name) &&
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/* Does the DIE have location information or external instance? */
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(dwarf_attr(die_mem, DW_AT_external, &attr) ||
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dwarf_attr(die_mem, DW_AT_location, &attr)))
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return DIE_FIND_CB_END;
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if (dwarf_haspc(die_mem, fvp->addr))
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return DIE_FIND_CB_CONTINUE;
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else
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