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 060E6C54EE9 for ; Fri, 16 Sep 2022 10:54:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229639AbiIPKyt (ORCPT ); Fri, 16 Sep 2022 06:54:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55242 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230503AbiIPKyG (ORCPT ); Fri, 16 Sep 2022 06:54:06 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3320BA99DD; Fri, 16 Sep 2022 03:38:43 -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 63B75CE1D26; Fri, 16 Sep 2022 10:38:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1FFC6C433B5; Fri, 16 Sep 2022 10:38:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1663324719; bh=fQQ9LRUqfsx3cfYecZ/0UH/3uQDGIYX4CW3obG1yBZ8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OzewtFsNS61ypGzXNK2PDmiBaEPZNyIkkIMymnIQXNEPqn+Q3M8xbXTEdBz6xbpwo zRT6AofFaPWxrMpqjCfxOz3bGBf4wNMeK49pD3POBxZ9sBQnxIT+AJZHKgdkG0wwR8 9M0cyS+qdIqTYT94EQiSP2IeCvyshuhVLLr6FWWuBKOE7T7reC7WNxcb0yyvK7f6z0 Xcu86W32cEBNJXdtM2lG9HPyqyfRoL35gLMw20IxnkRmkNQpzyKJybShqm8hiwIygT KQbFrehUKlkGr3zbHmXMRjeYE5Vx5+c9qbbSiAJmMiQWxv+ODqUIOASe5aCHaA7UIX eenodqYgWuRCA== From: guoren@kernel.org To: arnd@arndb.de, guoren@kernel.org, palmer@rivosinc.com, rostedt@goodmis.org, andy.chiu@sifive.com, greentime.hu@sifive.com, zong.li@sifive.com, jrtc27@jrtc27.com, mingo@redhat.com Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org Subject: [PATCH 1/3] riscv: ftrace: Fixup panic by disabling preemption Date: Fri, 16 Sep 2022 06:38:15 -0400 Message-Id: <20220916103817.9490-2-guoren@kernel.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220916103817.9490-1-guoren@kernel.org> References: <20220916103817.9490-1-guoren@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org From: Andy Chiu In RISCV, we must use an AUIPC + JALR pair to encode an immediate, forming a jump that jumps to an address over 4K. This may cause errors if we want to enable kernel preemption and remove dependency from patching code with stop_machine(). For example, if a task was switched out on auipc. And, if we changed the ftrace function before it was switched back, then it would jump to an address that has updated 11:0 bits mixing with previous XLEN:12 part. p: patched area performed by dynamic ftrace ftrace_prologue: p| REG_S ra, -SZREG(sp) p| auipc ra, 0x? ------------> preempted ... change ftrace function ... p| jalr -?(ra) <------------- switched back p| REG_L ra, -SZREG(sp) func: xxx ret Fixes: fc76b8b8011 ("riscv: Using PATCHABLE_FUNCTION_ENTRY instead of MCOUNT") Cc: Andy Chiu Signed-off-by: Guo Ren --- @Andy, could you give the patch a Signed-off-by? I just copy your most important comment, so the first author should be you. First, let's fix the problem caused by my previous patch, and you can continue your ftrace preemption work. --- arch/riscv/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index ed66c31e4655..b3454c843932 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -272,7 +272,7 @@ config ARCH_RV64I select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL select HAVE_FUNCTION_GRAPH_TRACER - select HAVE_FUNCTION_TRACER if !XIP_KERNEL + select HAVE_FUNCTION_TRACER if !XIP_KERNEL && !PREEMPTION select SWIOTLB if MMU endchoice -- 2.36.1