From patchwork Thu Nov 14 15:58:20 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alan Maguire X-Patchwork-Id: 13875318 Received: from mx0b-00069f02.pphosted.com (mx0b-00069f02.pphosted.com [205.220.177.32]) (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 C4D6713CFA8; Thu, 14 Nov 2024 15:58:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=205.220.177.32 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731599938; cv=none; b=GODH9QKbpDreXmfrmNn52pXSKzxl0LazIPrhlgGRcNUsYwxBeLaP4c0riZzxy2iyZHdKxW6dlKQGUpJAJAVy/eERzvUS4c0ZWvN/X1oEaDEUQ1vj8XzCYzbyFbrdGEbmOhQCne2d7Z3zt/Md7EyuxDw6qubZIKADHhpk2imch3A= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731599938; c=relaxed/simple; bh=akknOPtDEzMhCx0k8DD17IpqdLwjF7dEdYPts6lasj8=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=SKbDeYyeTurXEq9Yv2Y6kAYl/MfPWYFoQtl/31VAaEAYWjXbRor2AAzF2GeMOMKcHoCuto4ejv62ohRiamLQtsfVSYhy51P2uGUUsFyuRcflZ+hZzBaCN2qYiQFXYUo2sBNICGqSDbBfUsTljSRKScBm32X6Jfw9fQydZgGqdRg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=oracle.com; spf=pass smtp.mailfrom=oracle.com; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b=LAngA3nz; arc=none smtp.client-ip=205.220.177.32 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=oracle.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=oracle.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="LAngA3nz" Received: from pps.filterd (m0246630.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 4AED5lBQ002835; Thu, 14 Nov 2024 15:58:32 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=cc :content-transfer-encoding:date:from:message-id:mime-version :subject:to; s=corp-2023-11-20; bh=HoBr6ldOLBmkanIY8jw/Q51pEcvLN IwWCdWLLCet/bs=; b=LAngA3nzaucgVSq2gCbhjEly+s9Gz+Vpd6eX+yvk6j9E3 pxMJMYjhMS+gW1AUw+irDK3oaIVwERyWIwG7hSRKK6pyXz2UcgmlXGGlXHnYt3HH Z/UxnGIuOaZbLL3Msvwvj7q+eZzzb7amap3vCKl+Gn+kMppVBcIoXtlCmTBN5jrX YFKKYh8sBus9pTwOxBsabVQolSmAZ0mlO6AshTGNhTUmY1HhF1JavQGaelY9I/fB vqppVJ7BMlzCdI2m4BkXuoufRUMqc18xPXgwaT58VHqAlU7IX8pqc0i2C1ETfcSp RdDDgZ/S/2LUxb+MXQnp1ELXBb3641qiDq3mEag9A== Received: from iadpaimrmta03.imrmtpd1.prodappiadaev1.oraclevcn.com (iadpaimrmta03.appoci.oracle.com [130.35.103.27]) by mx0b-00069f02.pphosted.com (PPS) with ESMTPS id 42t0k5heh8-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 14 Nov 2024 15:58:32 +0000 (GMT) Received: from pps.filterd (iadpaimrmta03.imrmtpd1.prodappiadaev1.oraclevcn.com [127.0.0.1]) by iadpaimrmta03.imrmtpd1.prodappiadaev1.oraclevcn.com (8.18.1.2/8.18.1.2) with ESMTP id 4AEF9iEP000402; Thu, 14 Nov 2024 15:58:31 GMT Received: from pps.reinject (localhost [127.0.0.1]) by iadpaimrmta03.imrmtpd1.prodappiadaev1.oraclevcn.com (PPS) with ESMTPS id 42tbpad7cf-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 14 Nov 2024 15:58:31 +0000 Received: from iadpaimrmta03.imrmtpd1.prodappiadaev1.oraclevcn.com (iadpaimrmta03.imrmtpd1.prodappiadaev1.oraclevcn.com [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 4AEFwUgg002439; Thu, 14 Nov 2024 15:58:30 GMT Received: from bpf.uk.oracle.com (dhcp-10-175-214-128.vpn.oracle.com [10.175.214.128]) by iadpaimrmta03.imrmtpd1.prodappiadaev1.oraclevcn.com (PPS) with ESMTP id 42tbpad778-1; Thu, 14 Nov 2024 15:58:30 +0000 From: Alan Maguire To: acme@kernel.org Cc: yonghong.song@linux.dev, dwarves@vger.kernel.org, ast@kernel.org, andrii@kernel.org, bpf@vger.kernel.org, daniel@iogearbox.net, kernel-team@fb.com, song@kernel.org, eddyz87@gmail.com, olsajiri@gmail.com, Alan Maguire Subject: [PATCH v2 dwarves 0/2] Check DW_OP_[GNU_]entry_value for possible parameter matching Date: Thu, 14 Nov 2024 15:58:20 +0000 Message-ID: <20241114155822.898466-1-alan.maguire@oracle.com> X-Mailer: git-send-email 2.43.5 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-11-14_05,2024-11-13_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 mlxscore=0 malwarescore=0 mlxlogscore=999 spamscore=0 phishscore=0 adultscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2409260000 definitions=main-2411140125 X-Proofpoint-ORIG-GUID: U1MOKkqcPPs-69-lgkzhizGGWo0twAIq X-Proofpoint-GUID: U1MOKkqcPPs-69-lgkzhizGGWo0twAIq Currently, pahole relies on DWARF to find whether a particular func has its parameter mismatched with standard or optimized away. In both these cases, the func will not be put in BTF and this will prevent fentry/fexit tracing for these functions. The current parameter checking focuses on the first location/expression to match intended parameter register. But in some cases, the first location/expression does not have expected matching information, but further location like DW_OP_[GNU_]entry_value can provide information which matches the expected parameter register. Patch 1 supports this; patch 2 adds locking around dwarf_getlocation* as it is unsafe in a multithreaded environment. Run ~4000 times without observing a segmentation fault (as compared to without patch 2, where a segmentation fault is observed approximately every 200 invokations). Changes since v1: - used Eduard's approach of using a __dwarf_getlocations() internal wrapper (Eduard, patch 1). - renamed function to parameter__reg(); did not rename __dwarf_getlocations() since its functionality is based around retrieving DWARF location info rather than parameter register indices (Yonghong, patch 2) - added locking around dwarf_getlocation*() usage in dwarf_loader to avoid segmentation faults reported by Eduard (Jiri, Arnaldo, patch 2) Alan Maguire (1): dwarf_loader: use libdw__lock for dwarf_getlocation(s) Eduard Zingerman (1): dwarf_loader: Check DW_OP_[GNU_]entry_value for possible parameter matching dwarf_loader.c | 121 +++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 96 insertions(+), 25 deletions(-)