From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AA5E72C031E; Wed, 16 Sep 2026 13:54:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789566854; cv=none; b=KjOWUPD8XzC0mlzEPbk2jbIm2powUtewu3eHMIFCZCVNHYzb3yGJxPZTkzzC+MnwNuuYZqdupCuTzGPcp4hUELCTA0Ev2rTkDm68ECVarwLfp/1s/8PVdH/JEierG7x4hHCepH4mgCree3nn+Qvcq6wUnOqmiJ8AaXJ7LqClAcg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789566854; c=relaxed/simple; bh=eXSjVuZlgQ9gugywiLVJWnVCZ71Ql9z8vcAwRnTPQDw=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=aA03rSJAb8zwSf6RlS88xonghY6P0alALAq30j0nrqPPyv6qU03XfjFnC2gnbItK/fuSaVc+fWY0ZJkLwxCYQXjShe4g1rdAd7Rq5wBXhLb7DaFi7DOPwxyfTai9Q2Qug8EDm1YsTo53v2n2qYJdUxL1K27G34GkIDE8RC2Sssw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Xm2CR14X; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Xm2CR14X" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EBF321F00893; Wed, 16 Sep 2026 13:54:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789566848; bh=MM4Ho/XeNLJq7VZ5b/Z9Io2ZQ7TBT71DcUarT0QJgoo=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=Xm2CR14X9o5OMxnxQfYo/KEb2KgbZ+Ric0MvkdEXqD8W8QZTh5xWEJkVutNxrMMQ7 thH18xDxMqP0NRjPY6BquBh34e6DDHGPY2KTnzTRb9Ii1bEkQHQFUoWoVPQZl5gdTJ 8eO0vdA9Wak9TrcsUAYLaKGU1k9Oikpfcrm7VikV9Hv2ALkQv4Gedftv3rC6cyAJ87 TpwxhTv/zKdSLL/Gbz5iIxwPO/EpJk+PGIH6bNJv1bcvKPhCe9GZk1ppTbvMKPd2yG YrmsbMb0TCKcfgqhCIxepazAIthAMDshanqVD+2cgmkDwDpGzG5ve4AIJkLWfEAdKX XKgGQI3ppAa5g== Date: Wed, 16 Sep 2026 22:54:02 +0900 From: Masami Hiramatsu (Google) To: Namhyung Kim Cc: Arnaldo Carvalho de Melo , Ian Rogers , Jiri Olsa , Adrian Hunter , James Clark , Peter Zijlstra , Ingo Molnar , LKML , linux-perf-users@vger.kernel.org, Zecheng Li , Yanbo Zhao , Tengda Wu , Shuai Xue , Masami Hiramatsu Subject: Re: [PATCH v3 1/3] perf dwarf-aux: Add die_has_flex_array() helper Message-Id: <20260916225402.2002e60d2c737ae34cc520d2@kernel.org> In-Reply-To: <20260915064035.1970175-2-namhyung@kernel.org> References: <20260915064035.1970175-1-namhyung@kernel.org> <20260915064035.1970175-2-namhyung@kernel.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 14 Sep 2026 23:40:33 -0700 Namhyung Kim wrote: > The die_has_flex_array() returns true when the given type is a compound > type and contains an array at the end. To prevent an infinite recursion > add a depth field to the internal function. > This looks good to me. Acked-by: Masami Hiramatsu (Google) Thanks! > Cc: Masami Hiramatsu > Signed-off-by: Namhyung Kim > --- > tools/perf/util/dwarf-aux.c | 97 +++++++++++++++++++++++++++++++++++++ > tools/perf/util/dwarf-aux.h | 3 ++ > 2 files changed, 100 insertions(+) > > diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c > index d7160f87ac7d7ab3..a5aefe7d1d62d090 100644 > --- a/tools/perf/util/dwarf-aux.c > +++ b/tools/perf/util/dwarf-aux.c > @@ -7,6 +7,7 @@ > #include > #include > #include > +#include > #include "debug.h" > #include "dwarf-aux.h" > #include "dwarf-regs.h" > @@ -2180,3 +2181,99 @@ Dwarf_Die *die_deref_ptr_type(Dwarf_Die *ptr_die, int offset, > > return die_get_member_type(&type_die, offset, die_mem); > } > + > +static bool is_flex_array_member(Dwarf_Die *mb_die) > +{ > + Dwarf_Die type_die; > + Dwarf_Word size; > + > + /* get the type of the member */ > + if (die_get_real_type(mb_die, &type_die) == NULL) > + return false; > + > + if (dwarf_tag(&type_die) != DW_TAG_array_type) > + return false; > + > + return dwarf_aggregate_size(&type_die, &size) < 0 || size == 0; > +} > + > +#define MAX_FLEX_ARRAY_RECURSION 256 /* arbitrary */ > + > +static bool die_has_flex_array_recurse(Dwarf_Die *parent_die, int depth) > +{ > + Dwarf_Die die_mem, last_mb; > + int tag = dwarf_tag(parent_die); > + bool found = false; > + Dwarf_Word loc, last_loc = 0; > + > + if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type) > + return false; > + > + /* prevent infinite recursion */ > + if (depth > MAX_FLEX_ARRAY_RECURSION) > + return false; > + > + if (dwarf_child(parent_die, &die_mem)) > + return false; > + > + do { > + if (dwarf_tag(&die_mem) != DW_TAG_member) > + continue; > + > + if (tag == DW_TAG_union_type) { > + if (is_flex_array_member(&die_mem)) > + return true; > + > + if (die_get_real_type(&die_mem, &last_mb) && > + die_has_flex_array_recurse(&last_mb, depth + 1)) > + return true; > + } > + > + if (tag == DW_TAG_structure_type) { > + if (die_get_data_member_location(&die_mem, &loc) < 0) > + loc = 0; > + > + if (!found || last_loc < loc) { > + memcpy(&last_mb, &die_mem, sizeof(last_mb)); > + last_loc = loc; > + } > + } > + > + found = true; > + } while (dwarf_siblingof(&die_mem, &die_mem) == 0); > + > + if (tag == DW_TAG_structure_type && found) { > + if (is_flex_array_member(&last_mb)) > + return true; > + > + if (die_get_real_type(&last_mb, &die_mem)) > + return die_has_flex_array_recurse(&die_mem, depth + 1); > + } > + > + return false; > +} > + > +/** > + * die_has_flex_array - Check if the given type has a flex-array at the end > + * @type_die: a pointer to type DIE > + * > + * This function returns %true iff @type_die is a struct type and has an > + * array at the end. Note that the flex-array has no element, it should have > + * no size and the parent size doesn't include the flex-array. So it should > + * locate at the offset of the parent size. > + * > + * For simplicity, it assumes the parent size of aligned with the flex-array. > + */ > +bool die_has_flex_array(Dwarf_Die *type_die) > +{ > + Dwarf_Die real_type; > + > + if (dwarf_tag(type_die) == DW_TAG_typedef) { > + if (die_get_real_type(type_die, &real_type) == NULL) > + return false; > + > + type_die = &real_type; > + } > + > + return die_has_flex_array_recurse(type_die, 0); > +} > diff --git a/tools/perf/util/dwarf-aux.h b/tools/perf/util/dwarf-aux.h > index 161f0bf980b6ee6a..9b662db710220522 100644 > --- a/tools/perf/util/dwarf-aux.h > +++ b/tools/perf/util/dwarf-aux.h > @@ -189,4 +189,7 @@ void die_collect_global_vars(Dwarf_Die *cu_die, struct die_var_type **var_types) > /* Get the frame base information from CFA */ > int die_get_cfa(Dwarf *dwarf, u64 pc, int *preg, int *poffset); > > +/* Check whether given type has a flex array */ > +bool die_has_flex_array(Dwarf_Die *parent_die); > + > #endif /* _DWARF_AUX_H */ > -- > 2.55.0.1082.g2b9226bbc0-goog > -- Masami Hiramatsu (Google)