From owner-freebsd-mips@FreeBSD.ORG Tue Mar 13 14:48:22 2012 Return-Path: Delivered-To: freebsd-mips@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id F19E4106566B for ; Tue, 13 Mar 2012 14:48:22 +0000 (UTC) (envelope-from juli@clockworksquid.com) Received: from mail-wi0-f178.google.com (mail-wi0-f178.google.com [209.85.212.178]) by mx1.freebsd.org (Postfix) with ESMTP id 8698C8FC0A for ; Tue, 13 Mar 2012 14:48:22 +0000 (UTC) Received: by wibhq7 with SMTP id hq7so747782wib.13 for ; Tue, 13 Mar 2012 07:48:21 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc:content-type:x-gm-message-state; bh=EFI9Y5YVRYilO2wQBgTuw0R4hEUBXYRVwix5WzgerUQ=; b=mjE/w34fwj5hk7l4Hxs7E+XFl9G63xhYJ1HX4DmQkxCTOoDC+nynluwcia24+ihCbT 658wUWDPi+9YbItQ2sEuRU6J1MLXWUcGTO9KjmM5IjOLldp6bMjPyrdsrAuv+GItMPCk zsh7EToZSTzpdGCsM37WTfjo+E3IH1ut95BEFkGNl7753EiUFP4evNXGNcJPjouqIgL+ f/SnhW5skHEyW24C1ZiolDDIqDH5MK0iIa4zNEao1v9pjeRCcE0EuJyCKNuwEKC+pQx6 ikRkDypvROSPmp0VO8Y2bnKWe+Pqk/ulIRmDAWbocGt39iGDQ3j5kG/5bQduY8clNKvr QXRw== Received: by 10.180.88.67 with SMTP id be3mr8048283wib.20.1331650101241; Tue, 13 Mar 2012 07:48:21 -0700 (PDT) MIME-Version: 1.0 Received: by 10.180.96.231 with HTTP; Tue, 13 Mar 2012 07:48:00 -0700 (PDT) In-Reply-To: References: From: Juli Mallett Date: Tue, 13 Mar 2012 07:48:00 -0700 Message-ID: To: Andrew Duane Content-Type: text/plain; charset=UTF-8 X-Gm-Message-State: ALoCoQlP4iVMx1x7uTTgX6vDD6wSoXuiS5gwZR5yttivZ9uyw352KQxrapQ8wiqpPd0gZF+2hn/9 Cc: "freebsd-mips@FreeBSD.org" Subject: Re: Enforcing soft-float. X-BeenThere: freebsd-mips@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Porting FreeBSD to MIPS List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 13 Mar 2012 14:48:23 -0000 On Tue, Mar 13, 2012 at 06:35, Andrew Duane wrote: > If it can't be done safely/correctly, it can't be done. I would think > killing the program would be appropriate. > > Getting a wrong answer is catastrophic. My greatest concern is that any user program can use floating point instructions to panic the kernel by getting it to truncate its own pointers. Heck, an even slightly well-crafted program could probably predict likely values of the kernel stack pointer and set up many malicious userspace stacks that could match the truncated address, and get its own code running in kernel mode.