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 4AECC371D15; Sat, 19 Sep 2026 06:37:55 +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=1789799877; cv=none; b=CctwqSbtKoCz3Jb7ppaEgSgW8y9D8iCRzFnO+bQUnrY9ZLkWUQmAcLZIrwX41obp7nFdbCes5aL7CFfLA0ZU6/Q9utlJXEYROqqSHZMMhdFPUDo1nmrXBS4yHCMDTOXRBrIcH25umuvh6pog2s8cE2nDYax7gsO3ovYtzdIKLvU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789799877; c=relaxed/simple; bh=UFRbCyPFOpIhiJkgvdA1N7r2subnEKtJZgFjm96tkgg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tXt+X0LTUUU0Rj9AHnldc6UGbTACw9+cauBkaywIJLX70OLkM3U/iKF6Cw4lUJLBesbLl8IHb9panfeNZBEhVDGb7K8FnlZsEWgq0vtLBrLrrZbcLHMD71QDXD7qRdfLbIxRY/bLxHlkFc5KeGJezJNdIdlUFnn6KR9HRlgNvCw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DEZh4BL3; 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="DEZh4BL3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 191561F0089B; Sat, 19 Sep 2026 06:37:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789799873; bh=3r9HJ9ewao2icCySTmJJ7SlG5OXWYkY8ylhpaNhdIjI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=DEZh4BL3ibaxsHt9v7b8iP8yLmKBxqp7t16Nlq/vRG9hQcHFkyJWiVirLtM3dJc5k oC/LdC+KEyTf2GqIsRC25qpjnB8yFS0rD1qavfMc/ycCIRcrVukz9MmIGpbHMY5fBU 5S0DbQ/OJ70Gecd7GaeUFSEr3ynOi3X/tg1Zrgz+Ld0TNH4voUp1xqHDEObPKtNfdi uGk9DHoTl+ettOYDxnaCXTNQGvnXbYYHRlgkzVLAkBoBTmAlBTnzhmrOGotIyKFbee 5heGnUGI2Zq7DXmwXrKUzMddXOTEcacN9RZ7a1dE5UMkmhTOzyHbOrFr+FoI5Ien5F 9vPS9ZvC0JLyQ== 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 (Google)" Subject: [PATCH v5 1/4] perf dwarf-aux: Add die_has_flex_array() helper Date: Fri, 18 Sep 2026 23:37:42 -0700 Message-ID: <20260919063745.48444-2-namhyung@kernel.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260919063745.48444-1-namhyung@kernel.org> References: <20260919063745.48444-1-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. Acked-by: Masami Hiramatsu (Google) Signed-off-by: Namhyung Kim --- tools/perf/util/dwarf-aux.c | 107 ++++++++++++++++++++++++++++++++++++ tools/perf/util/dwarf-aux.h | 3 + 2 files changed, 110 insertions(+) diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c index d7160f87ac7d7ab3..1560e721479a1ac2 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 +2181,109 @@ 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) { + /* ignore bitfields */ + loc = 0; + } + + if (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 or union 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; + + switch (dwarf_tag(type_die)) { + case DW_TAG_typedef: + case DW_TAG_const_type: + case DW_TAG_restrict_type: + case DW_TAG_volatile_type: + case DW_TAG_shared_type: + if (die_get_real_type(type_die, &real_type) == NULL) + return false; + + type_die = &real_type; + break; + default: + break; + } + + 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