From patchwork Thu Oct 18 22:10:28 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Brad Smith X-Patchwork-Id: 10648329 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 BF8F414E2 for ; Thu, 18 Oct 2018 22:11:38 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id AE95528C75 for ; Thu, 18 Oct 2018 22:11:38 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 9FF0028C7B; Thu, 18 Oct 2018 22:11:38 +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 1460328C75 for ; Thu, 18 Oct 2018 22:11:37 +0000 (UTC) Received: from localhost ([::1]:45002 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gDGW1-0001SW-1q for patchwork-qemu-devel@patchwork.kernel.org; Thu, 18 Oct 2018 18:11:37 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55593) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gDGVM-00018N-6Q for qemu-devel@nongnu.org; Thu, 18 Oct 2018 18:10:56 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gDGVH-0001aA-LQ for qemu-devel@nongnu.org; Thu, 18 Oct 2018 18:10:53 -0400 Received: from speedy.comstyle.com ([2001:470:1d:8c::2]:16666 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 1gDGVD-0001BZ-S8 for qemu-devel@nongnu.org; Thu, 18 Oct 2018 18:10:49 -0400 Received: from mail.comstyle.com (localhost [127.0.0.1]) by mail.comstyle.com (Postfix) with ESMTP id 16E819843A for ; Thu, 18 Oct 2018 18:10:22 -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=8vZK1QRqd0IozDC1Tt4dS7Qs/gU=; b=bbXp+RhXiYStByoMI1IPLPz3ZvzO igjYFGkvmydWfwbCYrhSFkCQShkdphOT4/BWRBnLFxjK+GinhDFrgLadJHyJRX1E TU4+Cj1Pm9GbEJK5TCq6xVljXTr14dOnwE1cj/ONyXuwljpFJfiLLQflhr9gNgRS iSLtwi+QonAC78U= 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=R3iaKXobWLBSKp/Sh/zrerNMLg0B+YLEONEIIj2FDVIe/3xWmmd 8mpz4ygbGxy/uIXfAsJy7fdpVmlU6hFAvSy0nsGoW3FsPKNwTNQglAMWyV1NtyWs qvpc12sJpMhYzy9xcGFnADLORhBzQCXvbB3B4CM//MC9KuVuxhx86kzo= Received: from humpty.home.comstyle.com (unknown [IPv6:2001:470:c454:100:584c:84d6:1353:1133]) (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 64BD598439 for ; Thu, 18 Oct 2018 18:10:21 -0400 (EDT) Date: Thu, 18 Oct 2018 18:10:28 -0400 From: Brad Smith To: qemu-devel@nongnu.org Message-ID: <20181018221028.GB85911@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 v2] 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 -current and will be in our soon to be 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..7814e61114 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 +611,15 @@ 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. */ + 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();