From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from cmx-torrgo001.bell.net (mta-tor-005.bell.net [209.71.212.37]) (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 80BDC13698B; Thu, 15 Feb 2024 17:25:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.71.212.37 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708017927; cv=none; b=ACPPePT6WejiKzsUb+nf49jabthcYULm/f+zHJNdGekW/TlUuL4RtZdBSE+Ot19NaQKQRveLuNER8C05QLzGqXqn+81OLxt9V/7k6oVhQ407LV7V2GqSrq+k9kIW+etiilSc+Jcx8RjAdD7uSCAYUTiyl2pXnGqCCbJoeQJ1xA0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708017927; c=relaxed/simple; bh=YGF+xg9Zw2HpAEfB/LLNS8J3xoEcd0UnFW42VadKhTk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=L8z8VSzpyFvjV2E2E6y6eym/y3JoMgSlfVg6kq3LVXG0X6/dXKNoar8vkFzo5+ujZ+QDo8QJ39dBnqiT9pN/WgvB0hXjUWwppKwnDecdwXX4JennF/fkvgt2lTdwzbgKWpCdA+5MRDZBSfWwZZzK2vh7bAcKj8apR7kjiL3DC6k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=bell.net; spf=pass smtp.mailfrom=bell.net; dkim=pass (2048-bit key) header.d=bell.net header.i=@bell.net header.b=1VDP+dix; arc=none smtp.client-ip=209.71.212.37 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=bell.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bell.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bell.net header.i=@bell.net header.b="1VDP+dix" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bell.net; s=selector1; t=1708017925; bh=zaQaPX04GVXGx4EuNSfjTExmNxEJBUFZt8AtN9ccB6o=; h=Message-ID:Date:MIME-Version:Subject:To:References:From:In-Reply-To:Content-Type; b=1VDP+dixUeia2IAQ9nB44o3THF6eg+UXEi6JjWzO2edlDbvoFxxbfOfXiW+tuVLSlmuHGtKqFQQ6yB3dNyPaMioiNOIjtt7blMrsiGUQ09MJPr7aptIdokZF5oNi6X82QbGL8g9HBPvjEl/eMTnRUq3t/DnEI9RYALb74/LPr7+mjj1hTuKaFgUKOOOJ32I1rG3qhXlFLvk4nqVDd24X/JwcQt1paJvGjeN4ao6gDfFJ1sP7/FRUb7kCJALj+9StLtChltJaHUE5TKgiWy9G9AjFYUbwMCpA0TrzxygBA8fRqEM/P3+JPD0Ss4hINOW7pfeBMb+ILdPMrVBKBZgjqA== X-RG-SOPHOS: Clean X-RG-VADE-SC: 0 X-RG-VADE: Clean X-RG-Env-Sender: dave.anglin@bell.net X-RG-Rigid: 65CD68AA000FB6F2 X-RazorGate-Vade: gggruggvucftvghtrhhoucdtuddrgedvledrvddtgddutddtucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecuuefgnffnpdfqfgfvnecuuegrihhlohhuthemuceftddunecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpefkffggfgfuvfevfhfhjggtgfesthekredttddvjeenucfhrhhomheplfhohhhnucffrghvihguucetnhhglhhinhcuoegurghvvgdrrghnghhlihhnsegsvghllhdrnhgvtheqnecuggftrfgrthhtvghrnhepjeelffffjeehgffgueehleegfeegueeigedtkeffgeduueetffegffejudekgfeunecukfhppedugedvrdduvdeirdduuddvrddvfeefnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehhvghloheplgduledvrdduieekrddvrdeglegnpdhinhgvthepudegvddruddviedrudduvddrvdeffedpmhgrihhlfhhrohhmpegurghvvgdrrghnghhlihhnsegsvghllhdrnhgvthdpnhgspghrtghpthhtohepuddupdhrtghpthhtohepffgrvhhiugdrnfgrihhghhhtseetvegfnfetuedrvefqofdprhgtphhtthhopeflrghmvghsrdeuohhtthhomhhlvgihsehhrghnshgvnhhprghrthhnvghrshhhihhprdgtohhmpdhrtghpthhtoheprghkphhmsehlihhnuhigqdhfohhunhgurghtihhonhdrohhrghdprhgtphhtthhopegthhgrrhhlihgvsehrihhvohhsihhntgdrtghomhdprhgtphhtthhopegurghvvgdrrghnghhlihhnsegs vghllhdrnhgvthdprhgtphhtthhopeguvghllhgvrhesghhmgidruggv X-RazorGate-Vade-Verdict: clean 0 X-RazorGate-Vade-Classification: clean Received: from [192.168.2.49] (142.126.112.233) by cmx-torrgo001.bell.net (5.8.814) (authenticated as dave.anglin@bell.net) id 65CD68AA000FB6F2; Thu, 15 Feb 2024 12:25:03 -0500 Message-ID: Date: Thu, 15 Feb 2024 12:25:03 -0500 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 2/2] lib: checksum: Use aligned accesses for ip_fast_csum and csum_ipv6_magic tests Content-Language: en-US To: Guenter Roeck , David Laight , Charlie Jenkins , Palmer Dabbelt , Andrew Morton , Helge Deller , "James E.J. Bottomley" , Parisc List , Al Viro Cc: "linux-kernel@vger.kernel.org" References: <20240214-fix_sparse_errors_checksum_tests-v8-0-36b60e673593@rivosinc.com> <20240214-fix_sparse_errors_checksum_tests-v8-2-36b60e673593@rivosinc.com> <2ec91b11-23c7-4beb-8cef-c68367c8f029@roeck-us.net> <4723822c-2acf-4c41-899c-1e3d5659d1d8@bell.net> <1e302d8f-4e94-4278-b556-b8fc54956efb@roeck-us.net> From: John David Anglin Autocrypt: addr=dave.anglin@bell.net; keydata= xsFNBFJfN1MBEACxBrfJ+5RdCO+UQOUARQLSsnVewkvmNlJRgykqJkkI5BjO2hhScE+MHoTK MoAeKwoLfBwltwoohH5RKxDSAIWajTY5BtkJBT23y0hm37fN2JXHGS4PwwgHTSz63cu5N1MK n8DZ3xbXFmqKtyaWRwdA40dy11UfI4xzX/qWR3llW5lp6ERdsDDGHm5u/xwXdjrAilPDk/av d9WmA4s7TvM/DY3/GCJyNp0aJPcLShU2+1JgBxC6NO6oImVwW07Ico89ETcyaQtlXuGeXYTK UoKdEHQsRf669vwcV5XbmQ6qhur7QYTlOOIdDT+8zmBSlqBLLe09soATDciJnyyXDO1Nf/hZ gcI3lFX86i8Fm7lQvp2oM5tLsODZUTWVT1qAFkHCOJknVwqRZ8MfOvaTE7L9hzQ9QKgIKrSE FRgf+gs1t1vQMRHkIxVWb730C0TGiMGNn2oRUV5O5QEdb/tnH0Te1l+hX540adKZ8/CWzzW9 vcx+qD9IWLRyZMsM9JnmAIvYv06+YIcdpbRYOngWPd2BqvktzIs9mC4n9oU6WmUhBIaGOGnt t/49bTRtJznqm/lgqxtE2NliJN79dbZJuJWe5HkjVa7mP4xtsG59Rh2hat9ByUfROOfoZ0dS sVHF/N6NLWcf44trK9HZdT/wUeftEWtMV9WqxIwsA4cgSHFR2QARAQABzTdKb2huIERhdmlk IEFuZ2xpbiAoRGViaWFuIFBvcnRzKSA8ZGF2ZS5hbmdsaW5AYmVsbC5uZXQ+wsF3BBMBCAAh BQJSXzdTAhsDBQsJCAcDBRUKCQgLBRYCAwEAAh4BAheAAAoJEF2/za5fGU3xs/4P/15sNizR ukZLNYoeGAd6keRtNcEcVGEpRgzc/WYlXCRTEjRknMvmCu9z13z8qB9Y9N4JrPdp+NQj5HEs ODPI+1w1Mjj9R2VZ1v7suFwhjxMTUQUjCsgna1H+zW/UFsrL5ERX2G3aUKlVdYmSWapeGeFL xSMPzawPEDsbWzBzYLSHUOZexMAxoJYWnpN9JceEcGvK1SU2AaGkhomFoPfEf7Ql1u3Pgzie ClWEr2QHl+Ku1xW0qx5OLKHxntaQiu30wKHBcsF0Zx2uVGYoINJl/syazfZyKTdbmJnEYyNa Bdbn7B8jIkVCShLOWJ8AQGX/XiOoL/oE9pSZ60+MBO9qd18TGYByj0X2PvH+OyQGul5zYM7Q 7lT97PEzh8xnib49zJVVrKDdJds/rxFwkcHdeppRkxJH0+4T0GnU2IZsEkvpRQNJAEDmEE8n uRfssr7RudZQQwaBugUGaoouVyFxzCxdpSYL6zWHA51VojvJYEBQDuFNlUCqet9LtNlLKx2z CAKmUPTaDwPcS3uOywOW7WZrAGva1kz9lzxZ+GAwgh38HAFqQT8DQvW8jnBBG4m4q7lbaum3 znERv7kcfKWoWS7fzxLNTIitrbpYA3E7Zl9D2pDV3v55ZQcO/M35K9teRo6glrtFDU/HXM+r ABbh8u9UnADbPmJr9nb7J0tZUSS/zsFNBFJfN1MBEADBzhVn4XyGkPAaFbLPcMUfwcIgvvPF UsLi9Q53H/F00cf7BkMY40gLEXvsvdUjAFyfas6z89gzVoTUx3HXkJTIDTiPuUc1TOdUpGYP hlftgU+UqW5O8MMvKM8gx5qn64DU0UFcS+7/CQrKOJmzktr/72g98nVznf5VGysa44cgYeoA v1HuEoqGO9taA3Io1KcGrzr9cAZtlpwj/tcUJlc6H5mqPHn2EdWYmJeGvNnFtxd0qJDmxp5e YVe4HFNjUwsb3oJekIUopDksAP41RRV0FM/2XaPatkNlTZR2krIVq2YNr0dMU8MbMPxGHnI9 b0GUI+T/EZYeFsbx3eRqjv1rnNg2A6kPRQpn8dN3BKhTR5CA7E/cs+4kTmV76aHpW8m/NmTc t7KNrkMKfi+luhU2P/sKh7Xqfbcs7txOWB2V4/sbco00PPxWr20JCA5hYidaKGyQxuXdPUlQ Qja4WJFnAtBhh3Oajgwhbvd6S79tz1acjNXZ89b8IN7yDm9sQ+4LhWoUQhB5EEUUUVQTrzYS yTGN1YTTO5IUU5UJHb5WGMnSPLLArASctOE01/FYnnOGeU+GFIeQp91p+Jhd07hUr6KWYeJY OgEmu+K8SyjfggCWdo8aGy0H3Yr0YzaHeK2HrfC3eZcUuo+yDW3tnrNwM1rd1i3F3+zJK18q GnBxEQARAQABwsFfBBgBCAAJBQJSXzdTAhsMAAoJEF2/za5fGU3xNDQP/ikzh1NK/UBrWtpN yXLbype4k5/zyQd9FIBxAOYEOogfKdkp+Yc66qNf36gO6vsokxsDXU9me1n8tFoB/DCdzKbQ /RjKQRMNNR4fT2Q9XV6GZYSL/P2A1wzDW06tEI+u+1dV40ciQULQ3ZH4idBW3LdN+nloQf/C qoYkOf4WoLyhSzW7xdNPZqiJCAdcz9djN79FOz8US+waBCJrL6q5dFSvvsYj6PoPJkCgXhiJ hI91/ERMuK9oA1oaBxCvuObBPiFlBDNXZCwmUk6qzLDjfZ3wdiZCxc5g7d2e2taBZw/MsKFc k+m6bN5+Hi1lkmZEP0L4MD6zcPuOjHmYYzX4XfQ61lQ8c4ztXp5cKkrvaMuN/bD57HJ6Y73Q Y+wVxs9x7srl4iRnbulCeiSOAqHmwBAoWaolthqe7EYL4d2+CjPCcfIuK7ezsEm8c3o3EqC4 /UpL1nTi0rknRTGc0VmPef+IqQUj33GGj5JRzVJZPnYyCx8sCb35Lhs6X8ggpsafUkuKrH76 XV2KRzaE359RgbM3pNEViXp3NclPYmeu+XI8Ls/y6tSq5e/o/egktdyJj+xvAj9ZS18b10Jp e67qK8wZC/+N7LGON05VcLrdZ+FXuEEojJWbabF6rJGN5X/UlH5OowVFEMhD9s31tciAvBwy T70V9SSrl2hiw38vRzsl In-Reply-To: <1e302d8f-4e94-4278-b556-b8fc54956efb@roeck-us.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2024-02-15 12:06 p.m., Guenter Roeck wrote: > On 2/15/24 08:51, John David Anglin wrote: >> On 2024-02-15 10:44 a.m., Guenter Roeck wrote: >>> On 2/15/24 02:27, David Laight wrote: >>>> ... >>>>> It would be worthwhile tracking this down since there are >>>>> lots of unaligned data accesses (8-byte accesses on 4-byte aligned addresses) >>>>> when running the kernel in 64-bit mode. >>>> >>>> Hmmm.... >>>> For performance reasons you really don't want any of them. >>>> The misaligned 64bit fields need an __attribute((aligned(4)) marker. >>>> >>>> If the checksum code can do them it really needs to detect >>>> and handle the misalignment. >>>> >>>> The misaligned trap handler probably ought to contain a >>>> warn_on_once() to dump stack on the first such error. >>>> They can then be fixed one at a time. >>>> >>> >>> Unaligned LDD at unwind_once+0x4a8/0x5e0 >>> >>> Decoded: >>> >>> Unaligned LDD at unwind_once (arch/parisc/kernel/unwind.c:212 arch/parisc/kernel/unwind.c:243 arch/parisc/kernel/unwind.c:371 >>> arch/parisc/kernel/unwind.c:445) >>> >>> Source: >>> >>> static bool pc_is_kernel_fn(unsigned long pc, void *fn) >>> { >>>         return (unsigned long)dereference_kernel_function_descriptor(fn) == pc; >> This looks wrong to me.  Function descriptors should always be 8-byte aligned.  I think this >> routine should return false if fn isn't 8-byte aligned. > > Below you state "Code entry points only need 4-byte alignment." > > I think that contradicts each other. Also, the calling code is, > for example, >     pc_is_kernel_fn(pc, syscall_exit) > > I fail to see how this can be consolidated if it is ok > that syscall_exit is 4-byte aligned but, at the same time, > must be 8-byte aligned to be considered to be a kernel function. In the above call, syscall_exit is treated as a function pointer. It points to an 8-byte aligned function descriptor.  The descriptor holds the actual address of the function.  It only needs 4-byte alignment. Descriptors need 8-byte alignment for efficiency on 64-bit parisc. The pc and gp are accessed using ldd instructions. Dave -- John David Anglin dave.anglin@bell.net