From 0c188a07b6a399e3df66534c29fef0a2082aaf57 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Thu, 29 May 2014 19:52:32 +0900 Subject: [PATCH 1/2] perf probe: Fix a segfault if asked for variable it doesn't find Fix a segfault bug by asking for variable it doesn't find. Since the convert_variable() didn't handle error code returned from convert_variable_location(), it just passed an incomplete variable field and then a segfault was occurred when formatting the field. This fixes that bug by handling success code correctly in convert_variable(). Other callers of convert_variable_location() are correctly checking the return code. This bug was introduced by following commit. But another hidden erroneous error handling has been there previously (-ENOMEM case). commit 3d918a12a1b3088ac16ff37fa52760639d6e2403 Signed-off-by: Masami Hiramatsu Reported-by: Arnaldo Carvalho de Melo Tested-by: Arnaldo Carvalho de Melo Cc: Peter Zijlstra Cc: Paul Mackerras Cc: Ingo Molnar Cc: Namhyung Kim Link: http://lkml.kernel.org/r/20140529105232.28251.30447.stgit@ltc230.yrl.intra.hitachi.co.jp Signed-off-by: Jiri Olsa --- tools/perf/util/probe-finder.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c index 562762117639..9d8eb26f0533 100644 --- a/tools/perf/util/probe-finder.c +++ b/tools/perf/util/probe-finder.c @@ -511,12 +511,12 @@ 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) + 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) pr_err("Sorry, we don't support this variable location yet.\n"); - else if (pf->pvar->field) { + else if (ret == 0 && pf->pvar->field) { ret = convert_variable_fields(vr_die, pf->pvar->var, pf->pvar->field, &pf->tvar->ref, &die_mem); From 082f96a93eb5ba9bf771518a0dda590624568e8e Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Thu, 29 May 2014 21:19:30 +0900 Subject: [PATCH 2/2] 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 Tested-by: Arnaldo Carvalho de Melo Acked-by: Arnaldo Carvalho de Melo Cc: Arnaldo Carvalho de Melo Cc: Peter Zijlstra Cc: Paul Mackerras Cc: Ingo Molnar Cc: Namhyung Kim Link: http://lkml.kernel.org/r/20140529121930.30879.87092.stgit@ltc230.yrl.intra.hitachi.co.jp Signed-off-by: Jiri Olsa --- tools/perf/util/dwarf-aux.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c index 7defd77105d0..cc66c4049e09 100644 --- 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