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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4DC26C83F12 for ; Tue, 29 Aug 2023 15:14:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230128AbjH2POA (ORCPT ); Tue, 29 Aug 2023 11:14:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43454 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237177AbjH2PNi (ORCPT ); Tue, 29 Aug 2023 11:13:38 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 64CC0B5 for ; Tue, 29 Aug 2023 08:12:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1693321968; 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; bh=w3CVYpgxTsvHbKTea4nnprzsRm89plHSxyih6vxlw24=; b=Lq8lasQnnqxI8bvr0WCr2IZ0yYkEv5gsLhjDyUaJv/wH3WOgqsntBILX5+6gZjLHxhQU/3 lVhPCwtrpHD4+lKOQI5E9i6gkfpcMAUFhvExznrj20j2xmPX6WsVBU1/Jk13ZKBTUatcbo fEhKMu5k4vQGrfae6LyrN0XJ8p/c0WE= Received: from mimecast-mx02.redhat.com (66.187.233.73 [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-277-xaklgDF5NhOHUji6ZcH9AA-1; Tue, 29 Aug 2023 11:12:44 -0400 X-MC-Unique: xaklgDF5NhOHUji6ZcH9AA-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 0194A1C03D96; Tue, 29 Aug 2023 15:12:44 +0000 (UTC) Received: from redhat.com (unknown [10.22.16.28]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BE4FD401051; Tue, 29 Aug 2023 15:12:43 +0000 (UTC) Date: Tue, 29 Aug 2023 11:12:42 -0400 From: Joe Lawrence To: linuxppc-dev@lists.ozlabs.org Cc: live-patching@vger.kernel.org, Ryan Sullivan , Joe Lawrence Subject: Recent Power changes and stack_trace_save_tsk_reliable? Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org Hi ppc-dev list, We noticed that our kpatch integration tests started failing on ppc64le when targeting the upstream v6.4 kernel, and then confirmed that the in-tree livepatching kselftests similarly fail, too. From the kselftest results, it appears that livepatch transitions are no longer completing. Looking at the commit logs for v6.4, there looks to be some churn in the powerpc stack layout code -- I am suspicious that "reliable" stack unwinding may be left untested/broken after those changes. AFAICT, the livepatching subsystem is the only user of this interface in kernel/livepatch/transition.c :: klp_check_stack()'s call to stack_trace_save_tsk_reliable(). As such, the livepatching kselftests are probably the only way to test reliable unwinding. Unfortunately, git bisect isn't cooperating (we keep falling into a long span of non-bootable commits, despite efforts to `git bisect skip` over them), so we don't have an offending commit or patchset to point to. A few other details: - Test machine is a Power 9 9009-42A (IBM Power System S924) - Reproducable with v6.4, v6.5 - Minimal repro: -- Build with CONFIG_TEST_LIVEPATCH=m -- Run tools/testing/selftests/livepatch/test-livepatch.sh If this has already been report or fixed, please send any pointers to threads / commits. If not, I can provide any other info to help reproduce. Thanks, -- Joe