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 lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (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 626E3CC6B3C for ; Thu, 15 Oct 2026 11:23:16 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1xHJWM-00027Z-Me; Thu, 15 Oct 2026 07:21:14 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xHJWL-00026H-NB for qemu-devel@nongnu.org; Thu, 15 Oct 2026 07:21:13 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xHJWJ-00043i-Tt for qemu-devel@nongnu.org; Thu, 15 Oct 2026 07:21:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1792063271; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=vcE4vzjSzMZVA3M8g7QAKl6n6d9Iw1O4wO/Zs3KKo1U=; b=Vo5G2VhelwJifv47oyg+LOQOZRWEUkMEFcdxF3mGzj927Z7tqMgorQl3OCLk2/S+VUHKVC Vo+qmDhZrCKYWo2f9twJUo0kS9XZWopOm3NXSXnBzZeIPDy1usPm6KOX32tDs/QRhBKn4e nwIISePmoP/UJ4kCy8c6EoRiSwcjc10= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-643-a_HvIE3oPJyUZf2cEmYI0Q-1; Thu, 15 Oct 2026 11:21:08 +0000 X-MC-Unique: a_HvIE3oPJyUZf2cEmYI0Q-1 X-Mimecast-MFC-AGG-ID: a_HvIE3oPJyUZf2cEmYI0Q_1792063266 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A4C5A1956040; Thu, 15 Oct 2026 11:21:06 +0000 (UTC) Received: from berrange.csb (headnet04.pony-001.prod.iad2.dc.redhat.com [10.2.32.116]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 082341800257; Thu, 15 Oct 2026 11:21:02 +0000 (UTC) From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= To: qemu-devel@nongnu.org Cc: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , Michael Roth , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , Fabiano Rosas , Richard Henderson , "Dr. David Alan Gilbert" , Paolo Bonzini , Markus Armbruster , Pierrick Bouvier , Eric Blake , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , Laurent Vivier Subject: [PATCH 04/21] system: run SIGBUS handler on alternate signal stack Date: Thu, 15 Oct 2026 12:20:27 +0100 Message-ID: <20261015112044.1999748-5-berrange@redhat.com> In-Reply-To: <20261015112044.1999748-1-berrange@redhat.com> References: <20261015112044.1999748-1-berrange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 10 X-Spam_score: 1.0 X-Spam_bar: + X-Spam_report: (1.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.24, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org In preparation for introducing data recorder dumps during handling of of crash signals (BUS, SEGV, ILL, FPE, ABRT), introduce an alternative signal stack. This gives a known safe stack for code to operate under. This adds overhead of SIGSTKSZ bytes, which is OS-dependent, but on Linux is 8kb. Signed-off-by: Daniel P. Berrangé --- meson.build | 1 + system/signal.c | 14 +++++++++++++- 2 files changed, 14 insertions(+), 1 deletion(-) diff --git a/meson.build b/meson.build index 255c887e8e6..b383c7fceef 100644 --- a/meson.build +++ b/meson.build @@ -2647,6 +2647,7 @@ config_host_data.set('HAVE_GLIB_WITH_SLICE_ALLOCATOR', glib_has_gslice) config_host_data.set('HAVE_OPENPTY', cc.has_function('openpty', dependencies: util)) config_host_data.set('HAVE_STRCHRNUL', cc.has_function('strchrnul', prefix: osdep_prefix)) config_host_data.set('HAVE_SYSTEM_FUNCTION', cc.has_function('system', prefix: '#include ')) +config_host_data.set('CONFIG_SIGALTSTACK', cc.has_function('sigaltstack')) if rbd.found() config_host_data.set('HAVE_RBD_NAMESPACE_EXISTS', cc.has_function('rbd_namespace_exists', diff --git a/system/signal.c b/system/signal.c index 423325c9a1a..dc5a75e2816 100644 --- a/system/signal.c +++ b/system/signal.c @@ -26,6 +26,7 @@ #include "system/signal.h" #include "hw/core/cpu.h" #include "system/kvm.h" +#include "qemu/error-report.h" #ifdef CONFIG_LINUX @@ -89,12 +90,23 @@ void qemu_init_crash_signals(void) { struct sigaction action; +#ifdef CONFIG_SIGALTSTACK + static stack_t signal_stack; + signal_stack.ss_sp = (void *)g_new0(char, SIGSTKSZ); + signal_stack.ss_size = SIGSTKSZ; + if (sigaltstack(&signal_stack, NULL) < 0) { + error_printf("unable to enable alternate signal stack: %s", + strerror(errno)); + abort(); + } +#endif + /* * ALERT: when modifying this, take care that SIGBUS forwarding in * qemu_prealloc_mem() will continue working as expected. */ memset(&action, 0, sizeof(action)); - action.sa_flags = SA_SIGINFO; + action.sa_flags = SA_SIGINFO | SA_ONSTACK; action.sa_sigaction = sigbus_handler; sigaction(SIGBUS, &action, NULL); -- 2.56.0