From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-lj1-f180.google.com (mail-lj1-f180.google.com [209.85.208.180]) (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 E11BB54F85 for ; Mon, 8 Jan 2024 19:06:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Fi7rmwnU" Received: by mail-lj1-f180.google.com with SMTP id 38308e7fff4ca-2cd0f4f306fso24970671fa.0 for ; Mon, 08 Jan 2024 11:06:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1704740773; x=1705345573; darn=vger.kernel.org; h=mime-version:user-agent:content-transfer-encoding:autocrypt :references:in-reply-to:date:cc:to:from:subject:message-id:from:to :cc:subject:date:message-id:reply-to; bh=yA98EXpk94yYU68L5L4aM9oaAwCh5FYqhBcCy9p2l2g=; b=Fi7rmwnUGIM41XP65IV34FziZhG6ygnw5MkM585p54uBDPrMpQj5K2TTmGhNGf3wHw ekOMShIDsKWAxVqu3+ACudT6///d+wm88rxxMWIfNI+Gy/VN/2NhdzOofACPGXbZPPTg RdQf7l85NJMx5DuNa8T9G3zI2DuJtcz8DatqS1iM4qdfZpIaLGSJnA8D1vgRpYPAMyRQ +HEy0wwmvBQirIUR0Oud7TNyQarTZHUk5ZCh8JFdZ1Gn+xygCCDgtOX0hqYVpz58PMiO MGKscYKd/YhiEbsSiaBgYahEnPId6E0MaiokAZUZqV2MyQj+0iuY76F25w3BOVWJGs5r lIaQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1704740773; x=1705345573; h=mime-version:user-agent:content-transfer-encoding:autocrypt :references:in-reply-to:date:cc:to:from:subject:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=yA98EXpk94yYU68L5L4aM9oaAwCh5FYqhBcCy9p2l2g=; b=Ieo0TOa583oww4GMDDTxEC6v+++BKGokN6/N7hXKPVchasNueC5aOcXP8q6HO86W32 R4qdphBh6ziZzlagbxmIolXBJqDr7ZLloWI6bctSQhl6MJhY6emeFz/WTDZoEJbaGUZO tvYyhrxEI2T7SIcK2ZUbDlRMiXAZ40CwzJNZSP9GMV517hG9+srStJ/e9dqrrlDsiuuQ zu3kkJF012GiyinnkMaUx7MZOOCv1Idr0Oj9hDtWNPpJz8Ut+WhfUYfwjOljhrxsqYaL w8wjY/YmmHVXUgLoi6RXIiEaddQWPaKjxqIMfYQkK7NWWQCAM9ZOY1LGFSYA19i2P9Ct cxXw== X-Gm-Message-State: AOJu0YwodFEkbRSfceBZoAULY/MTdsm5hnsX2vq7t9TMhF69NOCNW5Q/ fc0ImOg0HSgd9bRdpd4EWIk= X-Google-Smtp-Source: AGHT+IFRqg4NpvptT0DGXPgsSsVEonyCXqRQ3U1Pm57OhyKvHVTLbp6yCDIo3tKQpKdUHenqgw0xcQ== X-Received: by 2002:a05:651c:1688:b0:2cc:8bd4:b860 with SMTP id bd8-20020a05651c168800b002cc8bd4b860mr1745703ljb.85.1704740772666; Mon, 08 Jan 2024 11:06:12 -0800 (PST) Received: from [192.168.1.95] (host-176-36-0-241.b024.la.net.ua. [176.36.0.241]) by smtp.gmail.com with ESMTPSA id x14-20020a2e7c0e000000b002ca092c194asm68612ljc.13.2024.01.08.11.06.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Jan 2024 11:06:12 -0800 (PST) Message-ID: Subject: Re: [PATCH bpf-next v2 1/2] bpf: Track aligned st store as imprecise spilled registers From: Eduard Zingerman To: Yonghong Song , Andrii Nakryiko Cc: bpf@vger.kernel.org, Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , kernel-team@fb.com, Martin KaFai Lau , Kuniyuki Iwashima , Martin KaFai Lau Date: Mon, 08 Jan 2024 21:06:10 +0200 In-Reply-To: <07d7d6e0-d090-47e6-9f17-0b083aeaa7af@linux.dev> References: <20240103232617.3770727-1-yonghong.song@linux.dev> <69410e766d68f4e69400ba9b1c3b4c56feaa2ca2.camel@gmail.com> <67a4b5b8bdb24a80c1289711c7c156b6c8247403.camel@gmail.com> <5e31a6835b648fae9880f6bfbc40801539b2d143.camel@gmail.com> <07d7d6e0-d090-47e6-9f17-0b083aeaa7af@linux.dev> Autocrypt: addr=eddyz87@gmail.com; prefer-encrypt=mutual; keydata=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 nYzhLWGcczc6J71q1Dje0l5vIPaSFOgwmWD4DA+WvuxM/shH4rtWeodbv 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 t1iq+gsfnXbPz5AnS598ScZI1oP7OrPSFJkt/z4acEbOQDQs8aUqrd46PV jsdqGvKnXZxzylux29UTNby4jTlz9pNJM+wPrDRmGfchLDUmf6CffaUYCbu4FiId+9+dcTCDvxbABRy1C3OJ8QY7cxfJ+pEZW18fRJ0XCl/fiV/ecAOfB3HsqgTzAn555h0rkFgay0hAvMU/mAW/CFNSIxV397zm749ZNLA0L2dMy1AKuOqH+/B+/ImBfJMDjmdyJQ8WU/OFRuGLdqOd2oZrA1iuPIa+yUYyZkaZfz/emQwpIL1+Q4p1R/OplA4yc301AqruXXUcVDbEB+joHW3hy5FwK5t5OwTKatrSJBkydSF9zdXy98fYzGniRyRA65P0Ix/8J3BYB4edY2/w0Ip/mdYsYQljBY0A== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.2 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2024-01-08 at 10:59 -0800, Yonghong Song wrote: [...] > I guess one way could be doing backtracking with "... =3D arr[i]" > is to have four ranges, [-32, -24), [-24, -16), [-16, -8), [-8, 0). > Later, when we see arr[i] =3D r0 and i has range [-32, 0). Since it cover= s [-32, -24), etc., > precision marking can proceed with 'r0'. But I guess this can potentially > increase verifier backtracking states a lot and is not scalable. Conserva= tively > doing precision marking with 'r0' (in arr[i] =3D r0) is a better idea. In theory it should be possible to collapse this range to min/max pair. But it is a complication, and I'd say it shouldn't be implemented unless we have evidence that it significantly improves verification performance. >=20 > Andrii has similar comments in > https://lore.kernel.org/bpf/CAEf4Bzb0LdSPnFZ-kPRftofA6LsaOkxXLN4_fr9BL= R3iG-te-g@mail.gmail.com/ >=20