From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59348) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1g9B7s-0003C0-Mx for qemu-devel@nongnu.org; Sun, 07 Oct 2018 11:37:49 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1g9B7r-0004Ff-V6 for qemu-devel@nongnu.org; Sun, 07 Oct 2018 11:37:48 -0400 Received: from speedy.comstyle.com ([2001:470:1d:8c::2]:27889 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 1g9B7r-0004Bt-N7 for qemu-devel@nongnu.org; Sun, 07 Oct 2018 11:37:47 -0400 Received: from mail.comstyle.com (localhost [127.0.0.1]) by mail.comstyle.com (Postfix) with ESMTP id 920059843A for ; Sun, 7 Oct 2018 11:37:24 -0400 (EDT) Received: from humpty.home.comstyle.com (unknown [IPv6:2001:470:c454:100:13af:4407:2bbf:771f]) (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 73E0D98439 for ; Sun, 7 Oct 2018 11:37:24 -0400 (EDT) Date: Sun, 7 Oct 2018 11:37:31 -0400 From: Brad Smith Message-ID: <20181007153731.GA32288@humpty.home.comstyle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Subject: [Qemu-devel] [PATCH] oslib-posix: Use MAP_STACK in qemu_alloc_stack() on OpenBSD List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org 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 diff --git a/util/oslib-posix.c b/util/oslib-posix.c index fbd0dc8c57..51e9a012c2 100644 --- a/util/oslib-posix.c +++ b/util/oslib-posix.c @@ -611,7 +611,11 @@ void *qemu_alloc_stack(size_t *sz) *sz += pagesz; ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE, - MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + MAP_PRIVATE | MAP_ANONYMOUS +#ifdef MAP_STACK + | MAP_STACK +#endif + , -1, 0); if (ptr == MAP_FAILED) { perror("failed to allocate memory for stack"); abort();