From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=95.215.58.228 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793825634; b=HkPQN3YJzvg/EKoKWt/X6QaxpkhRDEnyce+8CTAgadsHXfI8r0wCw1dLs2jO7pLrU/nq W553fzzUTst4Gs6ME4+W8OZYrX2PqCH2Iljs9UULPPNTJFOgGkD3H+K9O3vvhs2GISxyd 0j8agVPxY+oDSSxzlSUlrQUZaD97ecYc6+um95g0425DEU68VJLYAHLGeVNTQMs7jF9M1 nG+0saqB0gYQuGuPTAY/J+36aRRM3kJu+xxCEMIU8f2ie73i2RCsHzrJxrTuJ/YxEVrvA jpHhH6Utwc42fxjKjg7z4OWmme7C3oa4vYsYWhkxxkq3dXbYRH7Eo5bvezGIaMLhgLg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793825634; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:Message-ID:Date:MIME-Version:User-Agent: Subject:To:Cc:References:From:Content-Language:In-Reply-To: Content-Type:Content-Transfer-Encoding; bh=Y+PC7jHTM1E8Vn7cVLdmAfNEOuE8u386qwA62Ju0uyI=; b=noEeAPV9vZjLnPalUQYhBZDKi8WgYKpa7kvvH+N1QMVudH3f88bzjLmr84hOaqWMlVjP ur9cpvmFMpb9SJ2awxbAouTetDrZnBvc3N6dB2EIMR+iQLMzdwMvlXbdQ7BkbGN+HsKsr qUTIv+XpZMpfCYC+iB7icWz+YaWRkV9ziohp6PVE8TdeyQHVJbE+p00g6sZUUKaJm+x64 h5qzVEtsTOYVTRyuVut+vdlgB2kdv3FIEePb4Iv1v9zeICmiTpSM1IdLgxC5G6aC6lKJC zZftmOG9gle/3XPrj4IjsPt301KwZlnQq6LLhUJhyqqMLVadLbJWm36kmVA5c3Yp0nA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=Sb+q5FLD; arc=none smtp.remote-ip=95.215.58.228 Received: from mta1.migadu.com (out-228.mta1.migadu.com [95.215.58.228]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1476C606C910 for ; Wed, 4 Nov 2026 20:53:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 1476C606C910 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=Sb+q5FLD X-Envelope-To: bpf@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=2eu3NaYFL+BtaLJBYIyCWYYqp3hmqybleGi1ZXsiZxA=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793825630; v=1; x=1794430430; b=Sb+q5FLDG5lfdr3gkjg+cdm9VO9nU24kfKoqEa+tr2kwaitFJyDrj3nvrm8qGMmIyZn1XzK9 cUIUfO1pB7o44aZI5JDu9QXb9Bfn+tZeb/BTqX7Dk7dM4wDlP6k/iNfqdDep+wBnxZZTweq61CO iSKzKsKTzDAxbJaA6bJl/4IQ= X-Envelope-To: bpf@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id ef2066239f9c474a; Wed, 04 Nov 2026 20:53:50 +0000 X-Mizu-Trace-ID: ef2066239f9c474a X-Migadu-Flow: FLOW_OUT Message-ID: Date: Wed, 4 Nov 2026 12:53:46 -0800 X-Mailing-List: bpf@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf-next v3 01/12] bpf: Keep the 32-bit range across a sign extension that cannot change it To: Eduard Zingerman , ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, memxor@gmail.com Cc: martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, emil@etsalapatis.com, ihor.solodrai@linux.dev, john.fastabend@gmail.com, shuah@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org References: <20261020161907.2115379-1-vineet.gupta@linux.dev> <20261020161907.2115379-2-vineet.gupta@linux.dev> <9720ed1ff19dea17a1b379c02d7dd52ae886d807.camel@gmail.com> From: Vineet Gupta Content-Language: en-US In-Reply-To: <9720ed1ff19dea17a1b379c02d7dd52ae886d807.camel@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi Eduard, Thx for taking the time to review. On 10/29/26 3:30 PM, Eduard Zingerman wrote: > On Tue, 2026-10-20 at 09:18 -0700, Vineet Gupta wrote: > > ... > >> @@ -6192,6 +6193,27 @@ static void coerce_subreg_to_size_sx(struct bpf_reg_state *reg, int size) >> if (reg_umax(reg) < (1ULL << (num_bits - 1))) >> return; >> >> + if (size == 1) { >> + field_smin = S8_MIN; >> + field_smax = S8_MAX; >> + } else { >> + /* size == 2 */ >> + field_smin = S16_MIN; >> + field_smax = S16_MAX; >> + } >> + >> + /* >> + * The range already fits the field, so (sN)v == v for every value the >> + * register can hold and the sign extension changes nothing. The test >> + * above misses this once the range straddles zero: it only looks at >> + * reg_umax(), which a negative smin makes huge. > The `if (reg_umax(reg) < (1ULL << (num_bits - 1))) return` check is no > longer necessary, the new check below subsumes it. > Please drop it, otherwise commit lgtm. Agree. Dropped in v4. Thx, -Vineet > >> + * This has to precede reg_step_reset() below: the extension is a noop, >> + * so the base/step line still holds and there is nothing to discard. >> + */ >> + if (reg_s32_min(reg) >= field_smin && reg_s32_max(reg) <= field_smax) >> + return; >> + >> /* See comment at reg_step_check_unsigned(). */ >> reg_step_reset(reg); >>