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 24471C433EF for ; Mon, 14 Feb 2022 10:09:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345441AbiBNKJl (ORCPT ); Mon, 14 Feb 2022 05:09:41 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:35432 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345322AbiBNKGH (ORCPT ); Mon, 14 Feb 2022 05:06:07 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4679174630; Mon, 14 Feb 2022 01:49:29 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id C148761284; Mon, 14 Feb 2022 09:49:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 996D8C340E9; Mon, 14 Feb 2022 09:49:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1644832168; bh=3epFaGK+vhe/wOw2uqSsd6GvhL9Cvq9qJdaq6ifWC2k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=c6WOvrnq3jkKNnPSHQEmKHYz+LebrnnDY6Afx5Uh8NYA51NwLb1oDEjJX3nBGPSlU Udy3+cRvDu2t1CAGFosUfq3ZehN6iasoUcl0H1yWle3GDzh2xPc6AAWTZXiac7w2Oq sMslRlLYzchA/H8Z33c+iqqlWvFiwHvLa6OKxLtw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Changbin Du , Palmer Dabbelt Subject: [PATCH 5.15 068/172] riscv: eliminate unreliable __builtin_frame_address(1) Date: Mon, 14 Feb 2022 10:25:26 +0100 Message-Id: <20220214092508.750772172@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220214092506.354292783@linuxfoundation.org> References: <20220214092506.354292783@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Changbin Du commit 6a00ef4493706a23120057fafbc62379bcde11ec upstream. I tried different pieces of code which uses __builtin_frame_address(1) (with both gcc version 7.5.0 and 10.3.0) to verify whether it works as expected on riscv64. The result is negative. What the compiler had generated is as below: 31 fp = (unsigned long)__builtin_frame_address(1); 0xffffffff80006024 <+200>: ld s1,0(s0) It takes '0(s0)' as the address of frame 1 (caller), but the actual address should be '-16(s0)'. | ... | <-+ +-----------------+ | | return address | | | previous fp | | | saved registers | | | local variables | | $fp --> | ... | | +-----------------+ | | return address | | | previous fp --------+ | saved registers | $sp --> | local variables | +-----------------+ This leads the kernel can not dump the full stack trace on riscv. [ 7.222126][ T1] Call Trace: [ 7.222804][ T1] [] dump_backtrace+0x2c/0x3a This problem is not exposed on most riscv builds just because the '0(s0)' occasionally is the address frame 2 (caller's caller), if only ra and fp are stored in frame 1 (caller). | ... | <-+ +-----------------+ | | return address | | $fp --> | previous fp | | +-----------------+ | | return address | | | previous fp --------+ | saved registers | $sp --> | local variables | +-----------------+ This could be a *bug* of gcc that should be fixed. But as noted in gcc manual "Calling this function with a nonzero argument can have unpredictable effects, including crashing the calling program.", let's remove the '__builtin_frame_address(1)' in backtrace code. With this fix now it can show full stack trace: [ 10.444838][ T1] Call Trace: [ 10.446199][ T1] [] dump_backtrace+0x2c/0x3a [ 10.447711][ T1] [] show_stack+0x32/0x3e [ 10.448710][ T1] [] dump_stack_lvl+0x58/0x7a [ 10.449941][ T1] [] dump_stack+0x14/0x1c [ 10.450929][ T1] [] ubsan_epilogue+0x10/0x5a [ 10.451869][ T1] [] __ubsan_handle_load_invalid_value+0x6c/0x78 [ 10.453049][ T1] [] __pagevec_release+0x62/0x64 [ 10.455476][ T1] [] truncate_inode_pages_range+0x132/0x5be [ 10.456798][ T1] [] truncate_inode_pages+0x24/0x30 [ 10.457853][ T1] [] kill_bdev+0x32/0x3c ... Signed-off-by: Changbin Du Fixes: eac2f3059e02 ("riscv: stacktrace: fix the riscv stacktrace when CONFIG_FRAME_POINTER enabled") Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt Signed-off-by: Greg Kroah-Hartman --- arch/riscv/kernel/stacktrace.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) --- a/arch/riscv/kernel/stacktrace.c +++ b/arch/riscv/kernel/stacktrace.c @@ -22,15 +22,16 @@ void notrace walk_stackframe(struct task bool (*fn)(void *, unsigned long), void *arg) { unsigned long fp, sp, pc; + int level = 0; if (regs) { fp = frame_pointer(regs); sp = user_stack_pointer(regs); pc = instruction_pointer(regs); } else if (task == NULL || task == current) { - fp = (unsigned long)__builtin_frame_address(1); - sp = (unsigned long)__builtin_frame_address(0); - pc = (unsigned long)__builtin_return_address(0); + fp = (unsigned long)__builtin_frame_address(0); + sp = sp_in_global; + pc = (unsigned long)walk_stackframe; } else { /* task blocked in __switch_to */ fp = task->thread.s[0]; @@ -42,7 +43,7 @@ void notrace walk_stackframe(struct task unsigned long low, high; struct stackframe *frame; - if (unlikely(!__kernel_text_address(pc) || !fn(arg, pc))) + if (unlikely(!__kernel_text_address(pc) || (level++ >= 1 && !fn(arg, pc)))) break; /* Validate frame pointer */