From patchwork Fri Oct 19 12:52:39 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Brad Smith X-Patchwork-Id: 10649347 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4172A13A4 for ; Fri, 19 Oct 2018 12:53:57 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2F61228AC8 for ; Fri, 19 Oct 2018 12:53:57 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 242BB28ACF; Fri, 19 Oct 2018 12:53:57 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.7 required=2.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 8F93528AC8 for ; Fri, 19 Oct 2018 12:53:56 +0000 (UTC) Received: from localhost ([::1]:50261 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gDUHr-0003Sw-CR for patchwork-qemu-devel@patchwork.kernel.org; Fri, 19 Oct 2018 08:53:55 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50098) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gDUGh-0002Zd-Bq for qemu-devel@nongnu.org; Fri, 19 Oct 2018 08:52:44 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gDUGg-0004hA-Ie for qemu-devel@nongnu.org; Fri, 19 Oct 2018 08:52:43 -0400 Received: from speedy.comstyle.com ([2001:470:1d:8c::2]:5825 helo=mail.comstyle.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1gDUGg-0004dp-7z for qemu-devel@nongnu.org; Fri, 19 Oct 2018 08:52:42 -0400 Received: from mail.comstyle.com (localhost [127.0.0.1]) by mail.comstyle.com (Postfix) with ESMTP id 5E0B89843A for ; Fri, 19 Oct 2018 08:52:32 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=comstyle.com; h=date:from :to:subject:message-id:mime-version:content-type; s=selector1; bh=paGC/4xxPS5WwHWwNLPPNCxUeFg=; b=Zaashs8SOD4PUjAmG0O+X1iTiDQz 22pbr/NP8M8KKAXza0ymi/CcSLILckYEtXUFaP9GI0fVQGsuXiWJv8+Dhm9JGhhc JvuQlE9WOASiW3XzjNOiTMmylSaBWslaNKa7Z5bLEem6CPbwQqYMqM9Wx5ior8MV Tww0glVWMy0F5KI= DomainKey-Signature: a=rsa-sha1; c=nofws; d=comstyle.com; h=date:from:to :subject:message-id:mime-version:content-type; q=dns; s= selector1; b=Cida3gHM8HmRzd2mBUYYEgT916rG9naKrcR23IfKtnfaVnChZoD 8oZYw+SC3C6f48ZB3PWmrKaRYBu/D8jVAyIuLxS4W9tPaXf3PW17cPP6XDMOBiKG wJQ2sd9OL48zlYp96agllr2wJvhu9YkQQl7PeAorF/07jr88SN4hl8Uk= Received: from humpty.home.comstyle.com (unknown [IPv6:2001:470:c454:100:bae4:5a8f:59c0:49f6]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: brad) by mail.comstyle.com (Postfix) with ESMTPSA id 36A1298439 for ; Fri, 19 Oct 2018 08:52:32 -0400 (EDT) Date: Fri, 19 Oct 2018 08:52:39 -0400 From: Brad Smith To: qemu-devel@nongnu.org Message-ID: <20181019125239.GA13884@humpty.home.comstyle.com> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.10.1 (2018-07-13) X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2001:470:1d:8c::2 Subject: [Qemu-devel] [PATCH v3] oslib-posix: Use MAP_STACK in qemu_alloc_stack() on OpenBSD X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP Use MAP_STACK in qemu_alloc_stack() on OpenBSD. Added to our 6.4 release. MAP_STACK Indicate that the mapping is used as a stack. This flag must be used in combination with MAP_ANON and MAP_PRIVATE. Implement MAP_STACK option for mmap(). Synchronous faults (pagefault and syscall) confirm the stack register points at MAP_STACK memory, otherwise SIGSEGV is delivered. sigaltstack() and pthread_attr_setstack() are modified to create a MAP_STACK sub-region which satisfies alignment requirements. Observe that MAP_STACK can only be set/cleared by mmap(), which zeroes the contents of the region -- there is no mprotect() equivalent operation, so there is no MAP_STACK-adding gadget. Signed-off-by: Brad Smith Reviewed-by: Kamil Rytarowski Reviewed-by: Peter Maydell diff --git a/util/oslib-posix.c b/util/oslib-posix.c index fbd0dc8c57..c1bee2a581 100644 --- a/util/oslib-posix.c +++ b/util/oslib-posix.c @@ -596,6 +596,7 @@ pid_t qemu_fork(Error **errp) void *qemu_alloc_stack(size_t *sz) { void *ptr, *guardpage; + int flags; #ifdef CONFIG_DEBUG_STACK_USAGE void *ptr2; #endif @@ -610,8 +611,18 @@ void *qemu_alloc_stack(size_t *sz) /* allocate one extra page for the guard page */ *sz += pagesz; - ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE, - MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + flags = MAP_PRIVATE | MAP_ANONYMOUS; +#if defined(MAP_STACK) && defined(__OpenBSD__) + /* Only enable MAP_STACK on OpenBSD. Other OS's such as + * Linux/FreeBSD/NetBSD have a flag with the same name + * but have differing functionality. OpenBSD will SEGV + * if it spots execution with a stack pointer pointing + * at memory that was not allocated with MAP_STACK. + */ + flags |= MAP_STACK; +#endif + + ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE, flags, -1, 0); if (ptr == MAP_FAILED) { perror("failed to allocate memory for stack"); abort();