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 6823D424641; Tue, 15 Sep 2026 06:40:41 +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=1789454442; cv=none; b=J7wmfZy5kP9IajpIvYswKboeo6aJqmg7ikHkdvvuIZWGnBl0YCCirMBWo+nrPz49Bv/wed8xyflWPonbL9WtpKpBpdnw6ex52pzDq/73b9chtmTi8OB1rG8i2o/DchNc6NJtI/7wdA+l6XV1MeTAm02/8u8O95Llro9o29AMYgo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789454442; c=relaxed/simple; bh=5INeG7s+aX8SaHzUhq8rxK/zazt2ZoUWXJa/v3QX8Qg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=p8METDDl//xZ/8YjhqiG+bF+rFBUrNBP6YYB4+O+Omspbq9RHYeL7oShbIF8jMwMu0z5e9huj3dcv/bCPNcziJnUvaLjJ3XhzoovoASbTiG30flTrr4kCv+Ru939kXt0n5qL+qH6x+6hyx6yRIm50ELF8GP8BgoFqRnTUIHzOqw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VLa/uNY9; 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="VLa/uNY9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8C0F91F00899; Tue, 15 Sep 2026 06:40:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789454441; bh=qIENcBQsxO94LjSgl8tZtlEd/T8ffqoxUVG6SR+pF70=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=VLa/uNY9zz+NehQV9EizFSAliryGHdBW7PYEDeSs3xE/r+KSnNfOFabJ1ceTyQFFA 317amguQpUcxEEBbuEtliOE7nIHq545jmtreZQrvrKktOuDHqIRJm2d9mEcklG+chx PcoZDlwcA1f/z9+RkYlbgt1w94ZNukzLvl5CR03abPBEMIvxQmYek7iq+tmwRuw8KI tnpkMCiQXKk/asO9xhYxb8A59pvOOM6CVCJZ4LuStUBpbCKI1F9L8GRQRTBfmoCFxk xxnV3tpkmgSxn78r5u2hF7E6E1V/71RxgQS1fbWb8B4Sg8RlCdt/p3tB+yFPt1IkZi +9euZ0XO2O/LQ== 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 v3 1/3] perf dwarf-aux: Add die_has_flex_array() helper Date: Mon, 14 Sep 2026 23:40:33 -0700 Message-ID: <20260915064035.1970175-2-namhyung@kernel.org> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog In-Reply-To: <20260915064035.1970175-1-namhyung@kernel.org> References: <20260915064035.1970175-1-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 | 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