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 X-Spam-Level: X-Spam-Status: No, score=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 497D9C43461 for ; Mon, 19 Apr 2021 20:52:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 277A2611F0 for ; Mon, 19 Apr 2021 20:52:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243513AbhDSUw2 (ORCPT ); Mon, 19 Apr 2021 16:52:28 -0400 Received: from mail.kernel.org ([198.145.29.99]:54790 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239746AbhDSUt1 (ORCPT ); Mon, 19 Apr 2021 16:49:27 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 129C6613C7; Mon, 19 Apr 2021 20:46:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1618865172; bh=/n9hWrh5Ns6ElDZbq9sAMEb3XVD75y66iAlBuG07Ufc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Asp6IeT5CM6E1LYt73XTfO61oF8OuEnQ3D7cz5bV1J0w7iv6eBT1HdV9bqhrB6y/J bxwwEbUQJ18zVpf3NKNi7oFsMJseIzcXVp+IoRF66wIdYuFxZYpMmhtiZbgE+C97RC gCEk+NZLX4erLvwtrHLmnOrwq2hvEv/uVj27+apZgX+qr73+zP6ethS1IWPAjT3D4/ 7dgmOQ4wK1aDBuDbkz4zd7yd+YPbbbG5yOiQRH3cQ1SUv6iW/OykEe5QbrkmUVEs4q Dm2o97e54vYh0FQkZToJiuXy8qhH1Xe+pObN77dgfF+8gdCqabK2fdQrA0bMYSM7VO Bpt70x1vT5sqg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Vasily Gorbik , Sven Schnelle , Heiko Carstens , Sasha Levin , linux-s390@vger.kernel.org Subject: [PATCH AUTOSEL 4.4 2/7] s390/entry: save the caller of psw_idle Date: Mon, 19 Apr 2021 16:46:03 -0400 Message-Id: <20210419204608.7191-2-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210419204608.7191-1-sashal@kernel.org> References: <20210419204608.7191-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Vasily Gorbik [ Upstream commit a994eddb947ea9ebb7b14d9a1267001699f0a136 ] Currently psw_idle does not allocate a stack frame and does not save its r14 and r15 into the save area. Even though this is valid from call ABI point of view, because psw_idle does not make any calls explicitly, in reality psw_idle is an entry point for controlled transition into serving interrupts. So, in practice, psw_idle stack frame is analyzed during stack unwinding. Depending on build options that r14 slot in the save area of psw_idle might either contain a value saved by previous sibling call or complete garbage. [task 0000038000003c28] do_ext_irq+0xd6/0x160 [task 0000038000003c78] ext_int_handler+0xba/0xe8 [task *0000038000003dd8] psw_idle_exit+0x0/0x8 <-- pt_regs ([task 0000038000003dd8] 0x0) [task 0000038000003e10] default_idle_call+0x42/0x148 [task 0000038000003e30] do_idle+0xce/0x160 [task 0000038000003e70] cpu_startup_entry+0x36/0x40 [task 0000038000003ea0] arch_call_rest_init+0x76/0x80 So, to make a stacktrace nicer and actually point for the real caller of psw_idle in this frequently occurring case, make psw_idle save its r14. [task 0000038000003c28] do_ext_irq+0xd6/0x160 [task 0000038000003c78] ext_int_handler+0xba/0xe8 [task *0000038000003dd8] psw_idle_exit+0x0/0x6 <-- pt_regs ([task 0000038000003dd8] arch_cpu_idle+0x3c/0xd0) [task 0000038000003e10] default_idle_call+0x42/0x148 [task 0000038000003e30] do_idle+0xce/0x160 [task 0000038000003e70] cpu_startup_entry+0x36/0x40 [task 0000038000003ea0] arch_call_rest_init+0x76/0x80 Reviewed-by: Sven Schnelle Signed-off-by: Vasily Gorbik Signed-off-by: Heiko Carstens Signed-off-by: Sasha Levin --- arch/s390/kernel/entry.S | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S index 4cad1adff16b..d43f18b3d42c 100644 --- a/arch/s390/kernel/entry.S +++ b/arch/s390/kernel/entry.S @@ -889,6 +889,7 @@ ENTRY(ext_int_handler) * Load idle PSW. The second "half" of this function is in .Lcleanup_idle. */ ENTRY(psw_idle) + stg %r14,(__SF_GPRS+8*8)(%r15) stg %r3,__SF_EMPTY(%r15) larl %r1,.Lpsw_idle_lpsw+4 stg %r1,__SF_EMPTY+8(%r15) -- 2.30.2