From nobody Sun Sep 22 07:33:11 2024 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 B75A6C433F5 for ; Wed, 23 Feb 2022 02:24:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236789AbiBWCZK (ORCPT ); Tue, 22 Feb 2022 21:25:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38030 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233469AbiBWCZH (ORCPT ); Tue, 22 Feb 2022 21:25:07 -0500 Received: from mailgw01.mediatek.com (unknown [60.244.123.138]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E26F73969D for ; Tue, 22 Feb 2022 18:24:37 -0800 (PST) X-UUID: 1ce8197dbf7b4187aab88735c511e23c-20220223 X-UUID: 1ce8197dbf7b4187aab88735c511e23c-20220223 Received: from mtkcas10.mediatek.inc [(172.21.101.39)] by mailgw01.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-SHA384 256/256) with ESMTP id 67793427; Wed, 23 Feb 2022 10:24:31 +0800 Received: from mtkcas11.mediatek.inc (172.21.101.40) by mtkmbs10n1.mediatek.inc (172.21.101.34) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.2.792.15; Wed, 23 Feb 2022 10:24:30 +0800 Received: from mszsdtcf10.gcn.mediatek.inc (10.16.4.60) by mtkcas11.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Wed, 23 Feb 2022 10:24:29 +0800 From: Haibo Li To: Russell King , Matthias Brugger CC: "GitAuthor : Haibo Li" , , , , Subject: [PATCH] ARM:Fix incomplete stacktrace when unwind ftrace_regs_caller Date: Wed, 23 Feb 2022 10:24:28 +0800 Message-ID: <20220223022428.58385-1-haibo.li@mediatek.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-MTK: N Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" We can use register_ftrace_function(&ops) to register a function callback. if we set FTRACE_OPS_FL_SAVE_REGS in ftrace flags(flags in ops), then do stack unwind like dump_stack or WARN in the callback,we get incomplete stacktrace. The stack unwind ends in ftrace_regs_caller. Below is the output from test code. The test code do register_ftrace_function with FTRACE_OPS_FL_SAVE_REGS set, and set sysrq_handle_loglevel as filter,then do dump_stack in callback.It can not continue to unwind the stack from ftrace_regs_call echo 7 >/proc/sysrq-trigger sysrq: Changing Loglevel CPU: 1 PID: 145 Comm: sh Not tainted 5.17.0-rc4-00002-gb0dc07624ccd-dirty #2 [ 9.023226][ T145] Hardware name: Generic DT based system [ 9.023670][ T145] unwind_backtrace from show_stack+0x28/0x2c [ 9.024070][ T145] show_stack from dump_stack_lvl+0x48/0x54 [ 9.024298][ T145] dump_stack_lvl from ftrace_regs_call+0x4/0x18 [ 9.024650][ T145] sysrq: Loglevel set to 7 Fix it by adding unwind directives in ftrace_regs_caller. Signed-off-by: Haibo Li --- arch/arm/kernel/entry-ftrace.S | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S index a74289ebc803..eafa0c9b8992 100644 --- a/arch/arm/kernel/entry-ftrace.S +++ b/arch/arm/kernel/entry-ftrace.S @@ -75,15 +75,18 @@ =20 add ip, sp, #12 @ move in IP the value of SP as it was @ before the push {lr} of the mcount mechanism - + UNWIND(.movsp ip) str lr, [sp, #0] @ store LR instead of PC + UNWIND(.save{pc}) @it is the caller of ftrace_regs_caller =20 ldr lr, [sp, #8] @ get previous LR =20 str r0, [sp, #8] @ write r0 as OLD_R0 over previous LR =20 stmdb sp!, {ip, lr} + UNWIND(.save{ip,lr}) stmdb sp!, {r0-r11, lr} + UNWIND(.save{r0-r11,lr}) =20 @ stack content at this point: @ 0 4 48 52 56 60 64 68 72 --=20 2.25.1