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 558A9C43334 for ; Mon, 11 Jul 2022 09:58:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234159AbiGKJ6f (ORCPT ); Mon, 11 Jul 2022 05:58:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49062 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234160AbiGKJ6I (ORCPT ); Mon, 11 Jul 2022 05:58:08 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D858AB4BD9; Mon, 11 Jul 2022 02:27:15 -0700 (PDT) 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 sin.source.kernel.org (Postfix) with ESMTPS id 03BD6CE126E; Mon, 11 Jul 2022 09:27:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 16CA3C34115; Mon, 11 Jul 2022 09:27:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1657531631; bh=G3XdD4ZflwNdqfaY4yjkjFso/enpN8n0LYdk3KU1qK4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OQb3oxKDlGk3BXmyKcfFkk406Dqvl202qd6JJSNFMKndRGIlv3nlMClJhAash5i16 b3L8YbTrVL2DaBINa6syD0pY3YL2JJ6JG0sUgHhG8GkkNLSd2o8CxkcxSM4O2eDDf1 HKhnW6eOup39kHwvtsh8xJpS2BCnHsTpRn8NyRi8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alan Modra , Michael Ellerman , Segher Boessenkool , Sasha Levin Subject: [PATCH 5.15 135/230] powerpc/vdso: Fix incorrect CFI in gettimeofday.S Date: Mon, 11 Jul 2022 11:06:31 +0200 Message-Id: <20220711090607.893284695@linuxfoundation.org> X-Mailer: git-send-email 2.37.0 In-Reply-To: <20220711090604.055883544@linuxfoundation.org> References: <20220711090604.055883544@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: stable@vger.kernel.org From: Michael Ellerman [ Upstream commit 6d65028eb67dbb7627651adfc460d64196d38bd8 ] As reported by Alan, the CFI (Call Frame Information) in the VDSO time routines is incorrect since commit ce7d8056e38b ("powerpc/vdso: Prepare for switching VDSO to generic C implementation."). DWARF has a concept called the CFA (Canonical Frame Address), which on powerpc is calculated as an offset from the stack pointer (r1). That means when the stack pointer is changed there must be a corresponding CFI directive to update the calculation of the CFA. The current code is missing those directives for the changes to r1, which prevents gdb from being able to generate a backtrace from inside VDSO functions, eg: Breakpoint 1, 0x00007ffff7f804dc in __kernel_clock_gettime () (gdb) bt #0 0x00007ffff7f804dc in __kernel_clock_gettime () #1 0x00007ffff7d8872c in clock_gettime@@GLIBC_2.17 () from /lib64/libc.so.6 #2 0x00007fffffffd960 in ?? () #3 0x00007ffff7d8872c in clock_gettime@@GLIBC_2.17 () from /lib64/libc.so.6 Backtrace stopped: frame did not save the PC Alan helpfully describes some rules for correctly maintaining the CFI information: 1) Every adjustment to the current frame address reg (ie. r1) must be described, and exactly at the instruction where r1 changes. Why? Because stack unwinding might want to access previous frames. 2) If a function changes LR or any non-volatile register, the save location for those regs must be given. The CFI can be at any instruction after the saves up to the point that the reg is changed. (Exception: LR save should be described before a bl. not after) 3) If asychronous unwind info is needed then restores of LR and non-volatile regs must also be described. The CFI can be at any instruction after the reg is restored up to the point where the save location is (potentially) trashed. Fix the inability to backtrace by adding CFI directives describing the changes to r1, ie. satisfying rule 1. Also change the information for LR to point to the copy saved on the stack, not the value in r0 that will be overwritten by the function call. Finally, add CFI directives describing the save/restore of r2. With the fix gdb can correctly back trace and navigate up and down the stack: Breakpoint 1, 0x00007ffff7f804dc in __kernel_clock_gettime () (gdb) bt #0 0x00007ffff7f804dc in __kernel_clock_gettime () #1 0x00007ffff7d8872c in clock_gettime@@GLIBC_2.17 () from /lib64/libc.so.6 #2 0x0000000100015b60 in gettime () #3 0x000000010000c8bc in print_long_format () #4 0x000000010000d180 in print_current_files () #5 0x00000001000054ac in main () (gdb) up #1 0x00007ffff7d8872c in clock_gettime@@GLIBC_2.17 () from /lib64/libc.so.6 (gdb) #2 0x0000000100015b60 in gettime () (gdb) #3 0x000000010000c8bc in print_long_format () (gdb) #4 0x000000010000d180 in print_current_files () (gdb) #5 0x00000001000054ac in main () (gdb) Initial frame selected; you cannot go up. (gdb) down #4 0x000000010000d180 in print_current_files () (gdb) #3 0x000000010000c8bc in print_long_format () (gdb) #2 0x0000000100015b60 in gettime () (gdb) #1 0x00007ffff7d8872c in clock_gettime@@GLIBC_2.17 () from /lib64/libc.so.6 (gdb) #0 0x00007ffff7f804dc in __kernel_clock_gettime () (gdb) Fixes: ce7d8056e38b ("powerpc/vdso: Prepare for switching VDSO to generic C implementation.") Cc: stable@vger.kernel.org # v5.11+ Reported-by: Alan Modra Signed-off-by: Michael Ellerman Reviewed-by: Segher Boessenkool Link: https://lore.kernel.org/r/20220502125010.1319370-1-mpe@ellerman.id.au Signed-off-by: Sasha Levin --- arch/powerpc/kernel/vdso32/gettimeofday.S | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/vdso32/gettimeofday.S b/arch/powerpc/kernel/vdso32/gettimeofday.S index dd2099128b8f..42d40f895c1f 100644 --- a/arch/powerpc/kernel/vdso32/gettimeofday.S +++ b/arch/powerpc/kernel/vdso32/gettimeofday.S @@ -22,12 +22,15 @@ .macro cvdso_call funct call_time=0 .cfi_startproc PPC_STLU r1, -PPC_MIN_STKFRM(r1) + .cfi_adjust_cfa_offset PPC_MIN_STKFRM mflr r0 - .cfi_register lr, r0 PPC_STLU r1, -PPC_MIN_STKFRM(r1) + .cfi_adjust_cfa_offset PPC_MIN_STKFRM PPC_STL r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1) + .cfi_rel_offset lr, PPC_MIN_STKFRM + PPC_LR_STKOFF #ifdef __powerpc64__ PPC_STL r2, PPC_MIN_STKFRM + STK_GOT(r1) + .cfi_rel_offset r2, PPC_MIN_STKFRM + STK_GOT #endif get_datapage r5 .ifeq \call_time @@ -39,13 +42,15 @@ PPC_LL r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1) #ifdef __powerpc64__ PPC_LL r2, PPC_MIN_STKFRM + STK_GOT(r1) + .cfi_restore r2 #endif .ifeq \call_time cmpwi r3, 0 .endif mtlr r0 - .cfi_restore lr addi r1, r1, 2 * PPC_MIN_STKFRM + .cfi_restore lr + .cfi_def_cfa_offset 0 crclr so .ifeq \call_time beqlr+ -- 2.35.1