From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 01109CD4F52 for ; Mon, 18 May 2026 10:29:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=kkqg1A4tMCEZA3KMJi0cgPRzxq9yG3Wr6WbtOXIBt0c=; b=X4NNjRuwhcnYDQ qgFyJz7oW26ozqpppS5sEuKehPm9rtRcVPjNPr4uE6Cgis7I1AMxGFdq/vwOvgjDkSSN29TCZp4e0 VRmDhZ2VCGAazHkKPhu3cN6qbPsJCzfUkBQSTQs4E35Ou1YlH8JP57WHKR7/810fiHdch/noPgXyB NF4WD9hKtG15wFmtE4tj9aYb0NA6igB2wTScTsjeDLNrdMHufO/vfsF+bSoP35wsKSMO3HsvxjYyJ MoR1gLnAcVLvfY/ezeWrvxIvEZRtchWL8O9fPRBsD2DbRBBOAGSS28Y6wWlDQ+xIszPUh9kdHKty2 WCyAF2K4HR0cLaHcsXeA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wOvDN-0000000FDws-3ZRh; Mon, 18 May 2026 10:28:49 +0000 Received: from mail-wm1-x32c.google.com ([2a00:1450:4864:20::32c]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wOvDL-0000000FDuj-0ZKu for linux-riscv@lists.infradead.org; Mon, 18 May 2026 10:28:48 +0000 Received: by mail-wm1-x32c.google.com with SMTP id 5b1f17b1804b1-488a88aeec9so25013005e9.2 for ; Mon, 18 May 2026 03:28:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1779100125; x=1779704925; darn=lists.infradead.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=rYxpbaAOJBEg8u7pNfSvBgIfNUEd56wHaxd4vDulNaw=; b=TwyLFi6MoIAeNlNLIXj36ooOMAmbG9MteLrXXBkRntPc3OIBaMM8dhJ0DqZaCuWt5P eVxAQuzZAos8HzcihbjEtBacnRHLyvcpvw3lWQTRIYlZSLILN2FzIWzn8RY1rajJ973T mqWbn9LSvaATeskkHz8o1Xtt0vdoi2fs078mv4xCE21uNvvp3FKzl0YC1Wzd4aLExrWK 75sKJv0ZcNwci/bv2tkGmfHLoFlkI6baPMVNV+2Z9/60+XluHykYNQ28ohAIcw8DGCcC XneNhv5fDGEKFvsxYTDMJZEL6YaLxk63lJAzQBthadA7ysNR+sFzjlAwp1cNH8PM7wOn j0hw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779100125; x=1779704925; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=rYxpbaAOJBEg8u7pNfSvBgIfNUEd56wHaxd4vDulNaw=; b=VOFLWO39F6rHSKCX+ULJhtc0UOuU0bsPG8QwtUQeV8zYB2zRVgWO8De9VfJLVLK+r4 MnOujINp9J78C5gZaHNh+cdPLV9rU+hgIIjzmX5FYyI9a1nWLOcQyrVAU7/aSbJOisW8 Y6URE0WToXS+R8tjlGAmLjK162OSmHNQzF1h4Hd9Tt6BS1Y9jJq+QarOptCtQnefhSXW UqjJNgslVBnjJPDMyhwGAW1D1spmJfe13kfwMm1vnTAmks5YrCKKB3PBwCzG/VL8FeEo Znvs/RK3jZtMA6bly/IO+gptfaqkWWKErYTu5Lm32jC4PCxbTOZ9tah7SbhWx+GxLor/ DWYQ== X-Forwarded-Encrypted: i=1; AFNElJ8hhwTK0QM/gLq+Ni3ezJn3tkrT9zLfi1WeBbz2mMWATNvM708RXY0pj4TZ/4QOfWu9faqSxn4fdHFp5g==@lists.infradead.org X-Gm-Message-State: AOJu0Ywjm2+csPDw5MJ67gtVTAfMds6X1NT503e3SbS6vv3joGQV5kM4 5CorUW5DunHZXFstJYWXxoWc11pfX140c5hW9DzcuwVYXQ8YqwuN1cMX X-Gm-Gg: Acq92OEvlQd+CDMsdx5mw0Utcv27VnB4jnSh8KhJBXUbk05o6h7F9RcBeKrbRFlLtrY f8uzGf+pctH6g+Vcxi23dSZPuEABkkJ0WIE5G0NLkZvqD14yik6L1tcnCAEg+fJ6RclQwQAxOd2 8B2apq4LQH8CMoe5hSphQypqMOcxGD+Ega2BIaMmEbL+D8yywciTJAi+PTTYePKFP2jlpat0q2i 67UaauQE1Mrt/2mc/TPN5OLBpi8M4XS5xWXPtxgmeWGU63NvdDTHqWyQMo769rXMlUPl8Pm8fvw FM1gqZOs0F/uhOxry2xiVfzDc4QVzGmPs6eta/tD0A7/vNaZlDEsspud2+x5XrgGBIeV6WwT9vJ o+SyNB7jgI0YczcuZQz6X1TgWa0xL0dfrDiEVIBix8ONH6JYpY3tUICDcowcIYG25JtIQArh5Gi ViE3GCy+ejuJwlw6cTXPxiUgj6KNAt2nDkK9TFIdhP17bOemXBPsIhGuB+wAG+YPng X-Received: by 2002:a05:600d:10:b0:48f:e230:2a1b with SMTP id 5b1f17b1804b1-48fe6630137mr181624675e9.30.1779100124599; Mon, 18 May 2026 03:28:44 -0700 (PDT) Received: from pumpkin (82-69-66-36.dsl.in-addr.zen.co.uk. [82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48fffb9aac4sm234496915e9.9.2026.05.18.03.28.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 May 2026 03:28:43 -0700 (PDT) Date: Mon, 18 May 2026 11:28:42 +0100 From: David Laight To: Zong Li Cc: pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, debug@rivosinc.com, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] riscv: cif: reduce shadow stack size limit from 4GB to 2GB Message-ID: <20260518112842.07f0f2af@pumpkin> In-Reply-To: <20260518105725.7afe7a4c@pumpkin> References: <20260514075036.1432352-1-zong.li@sifive.com> <20260514095605.2c7d8761@pumpkin> <20260515102411.4d3e868a@pumpkin> <20260515201613.243ea49b@pumpkin> <20260518105725.7afe7a4c@pumpkin> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260518_032847_183657_C7597CF2 X-CRM114-Status: UNSURE ( 9.50 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Mon, 18 May 2026 10:57:25 +0100 David Laight wrote: .. > Actually would it be possible to initially just allocate one page? > If you get an overflow fault on the shadow stack I think you can > safely reallocate it at an entirely different user virtual address. > That would remove all the problems over committing a lot of swap. > Most threads will never do the 512 nested calls needed to blow the stack. Forget that - probably breaks setjmp(). -- David _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f50.google.com (mail-wm1-f50.google.com [209.85.128.50]) (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 346093074B1 for ; Mon, 18 May 2026 10:28:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.50 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779100135; cv=none; b=Q16ZTeBJsFk8GOp1WIZYLpcMuvUL3/JoUHhtoCEe+f1/dNnH0Cv/nsFZGCM3C5mfXdut7jQuivo43nc/Y/lfkdNBrMmsn4SepUWXbDv5UwpnAWFRqqw5AxR0mI+rVOTYM3veSoT01a5eACqgIUfuoE5kN1QIyn4r9+1ohzDCwdk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779100135; c=relaxed/simple; bh=rYxpbaAOJBEg8u7pNfSvBgIfNUEd56wHaxd4vDulNaw=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=FhM53TZMHDACIrmLKB88ylDlxn/WnRxFo3/mr+g3wHlQNApBikT3i0NOzqH7L0CYXDa3Q7WsJUFj6e6XKhhjSsQvL5ndiAkIdc53uUDiH0DUZ7awppzgAqrwsO8MIG9AzpT7cf04oh9sKz1OAn02bELUCeQkbSuBMNqfXeVNSTI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=k17TJ8r6; arc=none smtp.client-ip=209.85.128.50 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="k17TJ8r6" Received: by mail-wm1-f50.google.com with SMTP id 5b1f17b1804b1-48ff4f8ef0dso23936945e9.3 for ; Mon, 18 May 2026 03:28:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1779100125; x=1779704925; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=rYxpbaAOJBEg8u7pNfSvBgIfNUEd56wHaxd4vDulNaw=; b=k17TJ8r69P84AEIqgmk0vDVZb9GGJukxGVPklK1ig1kl1xGWjM13TQYXDEFuEIWI2X TpbMZKNWQ0PhqaKHQ4nKEhytBX4J94OK48T/zWQSrNKJuEO2MMynOwSVKGaYbWou18FJ XqmXc/ow3k7zKMidaq0NHlOZeMkvQgbb+eVDuLJlnipe3TE4bxCJJ99G+Qlt+B7X3pen ZTJU4p4+fhIy1nJdvsZ0kpdMX61WM+657HsB+77QP0uFp0APepPMvSyCgtjFjyoFJS77 WeJySrsAZKyoNDnZ3YlEfRcpWtLjLon/v+/6YwM78zTmQO/JEfprSl5UC+fO0S+77vqn ss/w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779100125; x=1779704925; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=rYxpbaAOJBEg8u7pNfSvBgIfNUEd56wHaxd4vDulNaw=; b=RlzDwxNSdal6rTRjyqSgIP9sHmz2yOIFspuT8iruqd5Bd7PGvkQn/QEXW1qCIcle4X j7rzO+dfe2ItqEwVV6Nv1QQt6azQQHfSNM7gUo5CWHofUJNG9Mb+Eog75ILDHPXbCVeT EjE8VJM4G6sjekkuweE5v28DteL5fQS7qCReK81fXP4YnH1/UKZwQpudXcwZV/02Vnk0 MwjQHp41xi3C8/QZJQAQJyFOc32ie9sZLdSg1LHWG6qGjieiOKNF3mmsKdeS8uF/hVPZ svid6ihfg3M2EZZpxUJrgHgWuRHuRQXn8D7FJq0CYc5P347w48b2xwL+0nmqk+tMAVgq bmPQ== X-Forwarded-Encrypted: i=1; AFNElJ/2kE78YLVmBtcGLXiS5ilLqDL4IrFGl8YqmxQ/vnlTq0XDEQfs2uBQJG+6w3jyBBTbF9ORXJC40UuxlbA=@vger.kernel.org X-Gm-Message-State: AOJu0YxzaCmlAYOzC+UJmTAVf6ZYF3zK6nWV8Jzo1eqzcANLmoFuzYWH d9Oau7j5fFn2dDqLSxh2cGpH7g/5Jt05rWotM+rQYlvxibRBj8fZdXjK X-Gm-Gg: Acq92OE9WYpPFlRmN5c+ZXltvIHdVLCjTX+NSM72cNm/ni0q54YV6sxI97F4yGsXsVV CgOIXPfcoZ5gNOpF1an3zwReBNIWzl33vsrqFiisnRFtP9uQ4BoxgjQ54pepwaF5ayDOZOC/v2n DV7txnyQ2msudSjTj9c5ILAz2FSPy79mWqH1q3coC2Fbid0XG5YX3WtuVj43R39DTIGlY0rbyNR 8LaGIfZOCqGGQuE9feLQ2N3HKW8MJEvoVMwk523B+t59mHs2T9xmAw6Jq4PgIVz8JOyIWm/XhCo 8lhr/xTKR0Q9fu646ETOjru/bZwSxOfx+Eq3khzG5x2mP2bQB8GgIHBluGbK6nfkeI4P+9kb6kV wDI0xz94Jg3Y2JQ4mYc+jHHa3MMIoz3m+CbOq26eRHq1m+OYrAqvO7HW8CiQtv+hWUN65EjMVaf lErLfUQWLn27TUN2XDv06riIhG+Rh84YHr0XRsSQwGJliNoqa8OPo2hfD6njaZNxAn X-Received: by 2002:a05:600d:10:b0:48f:e230:2a1b with SMTP id 5b1f17b1804b1-48fe6630137mr181624675e9.30.1779100124599; Mon, 18 May 2026 03:28:44 -0700 (PDT) Received: from pumpkin (82-69-66-36.dsl.in-addr.zen.co.uk. [82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48fffb9aac4sm234496915e9.9.2026.05.18.03.28.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 May 2026 03:28:43 -0700 (PDT) Date: Mon, 18 May 2026 11:28:42 +0100 From: David Laight To: Zong Li Cc: pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, debug@rivosinc.com, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] riscv: cif: reduce shadow stack size limit from 4GB to 2GB Message-ID: <20260518112842.07f0f2af@pumpkin> In-Reply-To: <20260518105725.7afe7a4c@pumpkin> References: <20260514075036.1432352-1-zong.li@sifive.com> <20260514095605.2c7d8761@pumpkin> <20260515102411.4d3e868a@pumpkin> <20260515201613.243ea49b@pumpkin> <20260518105725.7afe7a4c@pumpkin> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 18 May 2026 10:57:25 +0100 David Laight wrote: .. > Actually would it be possible to initially just allocate one page? > If you get an overflow fault on the shadow stack I think you can > safely reallocate it at an entirely different user virtual address. > That would remove all the problems over committing a lot of swap. > Most threads will never do the 512 nested calls needed to blow the stack. Forget that - probably breaks setjmp(). -- David