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SubjectRe: [PATCH perf/core ] perf-probe: Fix to track down unnamed union/structure members
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(2015/03/09 11:15), Masami Hiramatsu wrote:
> Fix perf probe to track down unnamed union/structure members.
> perf probe did not track down the tree of unnamed union/structure
> members, since it just failed to find given "name" in a parent
> structure/union. To solve this issue, I've introduced 2 changes.
>
> - Fix die_find_member() to track down the type-DIE if it is
> unnamed, and if it contains the specified member, returns the
> unnamed member.
> (note that we don't return found member, since unnamed member
> has the offset in the parent structure)
> - Fix convert_variable_fields() to track down the unnamed union/
> structure (one-by-one).
>
> With this patch, perf probe can access unnamed fields.
> -----
> #./perf probe -nfx ./perf lock__delete ops 'locked_ops=ops->locked.ops'
> Added new event:
> probe_perf:lock__delete (on lock__delete in /home/mhiramat/ksrc/linux-3/tools/perf/perf with ops locked_ops=ops->locked.ops)
>
> You can now use it in all perf tools, such as:
>
> perf record -e probe_perf:lock__delete -aR sleep 1
> -----
>
> The original report of this issue is: https://lkml.org/lkml/2015/3/5/431
>
> Reported-by: Arnaldo Carvalho de Melo <acme@kernel.org>
> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> ---
> tools/perf/util/dwarf-aux.c | 14 ++++++++++----
> tools/perf/util/probe-finder.c | 8 +++++++-
> 2 files changed, 17 insertions(+), 5 deletions(-)
>
> diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
> index 780b2bc..c34e024 100644
> --- a/tools/perf/util/dwarf-aux.c
> +++ b/tools/perf/util/dwarf-aux.c
> @@ -801,10 +801,16 @@ static int __die_find_member_cb(Dwarf_Die *die_mem, void *data)
> {
> const char *name = data;
>
> - if ((dwarf_tag(die_mem) == DW_TAG_member) &&
> - die_compare_name(die_mem, name))
> - return DIE_FIND_CB_END;
> -
> + if (dwarf_tag(die_mem) == DW_TAG_member) {
> + if (die_compare_name(die_mem, name))
> + return DIE_FIND_CB_END;
> + else if (!dwarf_diename(die_mem)) { /* Unnamed structure */
> + Dwarf_Die type_die, tmp_die;
> + if (die_get_type(die_mem, &type_die) &&
> + die_find_member(&type_die, name, &tmp_die))
> + return DIE_FIND_CB_END;
> + }
> + }
> return DIE_FIND_CB_SIBLING;
> }
>
> diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> index 46f009a..3898eba 100644
> --- a/tools/perf/util/probe-finder.c
> +++ b/tools/perf/util/probe-finder.c
> @@ -460,7 +460,8 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
> " nor array.\n", varname);
> return -EINVAL;
> }
> - if (field->ref) {
> + /* While prcessing unnamed field, we don't care about this */
> + if (field->ref && !dwarf_diename(vr_die)) {
> pr_err("Semantic error: %s must be referred by '.'\n",
> field->name);
> return -EINVAL;
> @@ -491,6 +492,11 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
> }
> ref->offset += (long)offs;
>
> + /* If this member is unnamed, we need to reuse this field */
> + if (!dwarf_diename(die_mem))
> + return convert_variable_fields(die_mem, varname, field,
> + &ref, die_mem);
> +
> next:
> /* Converting next field */
> if (field->next)
>
>


--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com




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