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 B942537DE9B; Mon, 14 Sep 2026 06:45:39 +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=1789368340; cv=none; b=ksCrapEQYs2Hx6T6wX0jgmjaLq+vms4TNHxvYz4C4BTqTRLTAzkrMYzY1wxEeO/QkUFOFZ0L3NutgSOlVlSVny/MUkkAfQLVHSXjXOw4kKs2G9CWsIiwBQtGyYvWHnb5Blat+msEVxTZcXaxVkJ3BC81sjRdSS97E2GWwexWrog= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789368340; c=relaxed/simple; bh=MGJ9Ucc4PWEmh8U7ndSvxUkdhbYFs9vV1DhMZpv+ssM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Fn6lqpKHZhbpLHDV01MUU4yTvHQj60hzobenn4GUqXa3Uy11vxaX010F1TjeqgZU5tkmX9dBkPfGBJJti6B41Q72IqXRDnDYXCymiNbnSHKVm0ywFtMuS9HCS4T4OeNJrCrtH+vPYetf8fItI0IK+iJhn3XLNImCpiam+Ue4WVg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lw1GWC4H; 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="lw1GWC4H" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D82071F00898; Mon, 14 Sep 2026 06:45:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789368339; bh=ymdYKBbVAY1WyUZy4e/FNcP10X3wEv3fOcy73P04PFw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=lw1GWC4HGoazzLOzbso/NpzFMV8qeociYKYcm8AGThhuX24PlapEs2eAVRCVOGeOk eMOsdbIMF3MSLk6/MBwgyB3yDTHU+6ZSCI/I4d8sBrFgFoJeQM6yu2x8a54Ew8xRU0 Zbj9H1QWOjiinrN5kYahZMneIFCPk2pItDagnCXpLmpiVbmlFkKhBqrW9IjslSPzqi Rg6FRv5RxhzRAUSljbONzeWZAUgl6H2MRkN+wKx11wqf7warTeEsZDcWn+huDPwD9a gIpP0GLTrBB4uzW4IvieSA842bG+YhnmJQy3Lkzqr79OSzJ1gH24Nc+/SkdXYCM1SW RqmVVIxMZ/T7g== From: Namhyung Kim To: Arnaldo Carvalho de Melo Cc: 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: [PATCH v2 2/4] perf dwarf-aux: Add die_has_flex_array() helper Date: Sun, 13 Sep 2026 23:45:33 -0700 Message-ID: <20260914064535.1671939-3-namhyung@kernel.org> X-Mailer: git-send-email 2.55.0.1032.g73a4cd73de-goog In-Reply-To: <20260914064535.1671939-1-namhyung@kernel.org> References: <20260914064535.1671939-1-namhyung@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. Cc: Masami Hiramatsu Signed-off-by: Namhyung Kim --- tools/perf/util/dwarf-aux.c | 77 +++++++++++++++++++++++++++++++++++++ tools/perf/util/dwarf-aux.h | 3 ++ 2 files changed, 80 insertions(+) diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c index d7160f87ac7d7ab3..465824e6513eb0ac 100644 --- a/tools/perf/util/dwarf-aux.c +++ b/tools/perf/util/dwarf-aux.c @@ -2180,3 +2180,80 @@ 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); + + 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) + memcpy(&last_mb, &die_mem, sizeof(last_mb)); + + } while (dwarf_siblingof(&die_mem, &die_mem) == 0); + + if (tag == DW_TAG_structure_type) { + 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 + * @parent_die: a pointer to type DIE + * + * This function returns %true iff @parent_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 *parent_die) +{ + return die_has_flex_array_recurse(parent_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 */ -- 2.55.0.1032.g73a4cd73de-goog