From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from 66-220-155-178.mail-mxout.facebook.com (66-220-155-178.mail-mxout.facebook.com [66.220.155.178]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 09D1733D4EE for ; Fri, 20 Mar 2026 19:09:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=66.220.155.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774033784; cv=none; b=MvcxqvcKOwL8tWRxeOkHOklCzcrXxtXLYj66q/P7n2NK8YbJ+Yqpu7MJvYsAng7BassUK53WtWWpzjy4bRCaAiRXT0q4t/tUwFcUtSsp2mOlPgHy32M3NRXQxU9W+ogp10cJj2yAtYTW3n4+OwMOTRXZgyawmLGYL56E6S5l7Ac= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774033784; c=relaxed/simple; bh=zcFQscBDswAelpsHw0NQpSHwQlpjn7RoznAsSiTN1rw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=LkxFdFmTIOLMzspN0V8LuZif6lw54291eQluhbLolzkPo/qMnCqUORr3DsQqX0j1q3Wqce1C92xL+4fNLIVThMXGoCKmfBdnO0pj/Y3pjiDY8/vO9v52JZ57G4eh/udEhDdVq90WYO608XT3tD1Iu/nv6/dWtQTo1BOHt2X4hT0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev; spf=fail smtp.mailfrom=linux.dev; arc=none smtp.client-ip=66.220.155.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=linux.dev Received: by devvm16039.vll0.facebook.com (Postfix, from userid 128203) id C182F2A7EACF6; Fri, 20 Mar 2026 12:09:27 -0700 (PDT) From: Yonghong Song To: Alan Maguire , Arnaldo Carvalho de Melo , dwarves@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , bpf@vger.kernel.org, kernel-team@fb.com Subject: [PATCH dwarves v3 2/9] dwarf_loader: Handle signatures with dead arguments Date: Fri, 20 Mar 2026 12:09:27 -0700 Message-ID: <20260320190927.1970829-1-yonghong.song@linux.dev> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260320190917.1970524-1-yonghong.song@linux.dev> References: <20260320190917.1970524-1-yonghong.song@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable For llvm dwarf, the dead argument may be in the middle of DW_TAG_subprogram. So we introduce skip_idx in order to match expected registers properly. For example: 0x00042897: DW_TAG_subprogram DW_AT_name ("create_dev") DW_AT_calling_convention (DW_CC_nocall) DW_AT_type (0x0002429a "int") ... 0x000428ab: DW_TAG_formal_parameter DW_AT_name ("name") DW_AT_type (0x000242ed "char *") ... 0x000428b5: DW_TAG_formal_parameter DW_AT_location (indexed (0x3f) loclist =3D 0x0= 00027f8: [0xffffffff87681370, 0xffffffff8768137a): DW_OP_re= g5 RDI [0xffffffff8768137a, 0xffffffff87681392): DW_OP_re= g3 RBX [0xffffffff87681392, 0xffffffff876813ae): DW_OP_en= try_value(DW_OP_reg5 RDI), DW_OP_stack_value) DW_AT_name ("dev") DW_AT_type (0x00026859 "dev_t") ... With skip_idx, we can identify that the second original argument 'dev' becomes the first one after optimization. Signed-off-by: Yonghong Song --- dwarf_loader.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/dwarf_loader.c b/dwarf_loader.c index 21f8bf1..a6e6587 100644 --- a/dwarf_loader.c +++ b/dwarf_loader.c @@ -1192,6 +1192,7 @@ static ptrdiff_t __dwarf_getlocations(Dwarf_Attribu= te *attr, =20 struct func_info { bool signature_changed; + int skip_idx; }; =20 /* For DW_AT_location 'attr': @@ -1264,6 +1265,7 @@ static struct parameter *parameter__new(Dwarf_Die *= die, struct cu *cu, if (parm !=3D NULL) { bool has_const_value; Dwarf_Attribute attr; + int reg_idx; =20 tag__init(&parm->tag, cu, die); parm->name =3D attr_string(die, DW_AT_name, conf); @@ -1273,7 +1275,18 @@ static struct parameter *parameter__new(Dwarf_Die = *die, struct cu *cu, if (!info->signature_changed) { if (cu->producer_clang || param_idx >=3D cu->nr_register_params) return parm; + } else { + /* if true_signature is not enabled, mark parameter as + * unexpected_reg since there is a skipped parameter before. + */ + if (!conf->true_signature && info->skip_idx) { + parm->unexpected_reg =3D 1; + return parm; + } } + reg_idx =3D param_idx - info->skip_idx; + if (reg_idx >=3D cu->nr_register_params) + return parm; /* Parameters which use DW_AT_abstract_origin to point at * the original parameter definition (with no name in the DIE) * are the result of later DWARF generation during compilation @@ -1311,7 +1324,7 @@ static struct parameter *parameter__new(Dwarf_Die *= die, struct cu *cu, parm->has_loc =3D dwarf_attr(die, DW_AT_location, &attr) !=3D NULL; =20 if (parm->has_loc) { - int expected_reg =3D cu->register_params[param_idx]; + int expected_reg =3D cu->register_params[reg_idx]; int actual_reg =3D parameter__reg(&attr, expected_reg); =20 if (actual_reg < 0) @@ -1324,8 +1337,10 @@ static struct parameter *parameter__new(Dwarf_Die = *die, struct cu *cu, * contents. */ parm->unexpected_reg =3D 1; - } else if (has_const_value) { + } else if (has_const_value || info->signature_changed) { parm->optimized =3D 1; + if (info->signature_changed) + info->skip_idx++; } } =20 --=20 2.52.0