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 573DAC6FD1C for ; Wed, 22 Mar 2023 09:02:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229905AbjCVJCG (ORCPT ); Wed, 22 Mar 2023 05:02:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46316 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229611AbjCVJCD (ORCPT ); Wed, 22 Mar 2023 05:02:03 -0400 Received: from mail-m118111.qiye.163.com (mail-m118111.qiye.163.com [115.236.118.111]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5D5D95B42A; Wed, 22 Mar 2023 02:02:01 -0700 (PDT) Received: from [10.128.10.193] (unknown [117.133.56.22]) by mail-m118111.qiye.163.com (Hmail) with ESMTPA id 9E5CB5807BE; Wed, 22 Mar 2023 17:01:55 +0800 (CST) Message-ID: <88c2c37b-c221-5c27-9663-7026084adf8d@sangfor.com.cn> Date: Wed, 22 Mar 2023 17:01:54 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH v5 1/2] function_graph: Support recording and printing the return value of function Content-Language: en-US To: "Russell King (Oracle)" Cc: mhiramat@kernel.org, rostedt@goodmis.org, mark.rutland@arm.com, will@kernel.org, catalin.marinas@arm.com, palmer@dabbelt.com, paul.walmsley@sifive.com, tglx@linutronix.de, dave.hansen@linux.intel.com, x86@kernel.org, mingo@redhat.com, xiehuan09@gmail.com, dinghui@sangfor.com.cn, huangcun@sangfor.com.cn, dolinux.peng@gmail.com, linux-trace-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20230320131650.482594-1-pengdonglin@sangfor.com.cn> <20230320131650.482594-2-pengdonglin@sangfor.com.cn> From: Donglin Peng In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-HM-Spam-Status: e1kfGhgUHx5ZQUpXWQgPGg8OCBgUHx5ZQUlOS1dZFg8aDwILHllBWSg2Ly tZV1koWUFITzdXWS1ZQUlXWQ8JGhUIEh9ZQVkaTx4eVkwdS0NOT04YGR0eTFUTARMWGhIXJBQOD1 lXWRgSC1lBWUpKTFVKSEhVTk1VSUlZV1kWGg8SFR0UWUFZT0tIVUpKS09ISFVKS0tVS1kG X-HM-Sender-Digest: e1kMHhlZQR0aFwgeV1kSHx4VD1lBWUc6PC46GSo*Kj0OKRRJLRI3QiE2 NwNPFA9VSlVKTUxCT0xOTEpMS01MVTMWGhIXVQseFRwfFBUcFxIVOwgaFRwdFAlVGBQWVRgVRVlX WRILWUFZSkpMVUpISFVOTVVJSVlXWQgBWUFPTU1DNwY+ X-HM-Tid: 0a87088db1662eb7kusn9e5cb5807be X-HM-MType: 1 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/3/22 1:31, Russell King (Oracle) wrote: > On Mon, Mar 20, 2023 at 06:16:49AM -0700, Donglin Peng wrote: >> diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S >> index 3e7bcaca5e07..ba1986e27af8 100644 >> --- a/arch/arm/kernel/entry-ftrace.S >> +++ b/arch/arm/kernel/entry-ftrace.S >> @@ -258,7 +258,15 @@ ENDPROC(ftrace_graph_regs_caller) >> #ifdef CONFIG_FUNCTION_GRAPH_TRACER >> ENTRY(return_to_handler) >> stmdb sp!, {r0-r3} >> +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL >> + /* >> + * Pass both the function return values in the register r0 and r1 >> + * to ftrace_return_to_handler >> + */ >> + add r2, sp, #16 @ sp at exit of instrumented routine >> +#else >> add r0, sp, #16 @ sp at exit of instrumented routine >> +#endif >> bl ftrace_return_to_handler > ... >> -unsigned long ftrace_return_to_handler(unsigned long frame_pointer) >> +static unsigned long __ftrace_return_to_handler(unsigned long retval_1st, >> + unsigned long retval_2nd, unsigned long frame_pointer) > ... >> +#ifdef CONFIG_FUNCTION_GRAPH_RETVAL >> +unsigned long ftrace_return_to_handler(unsigned long retval_1st, >> + unsigned long retval_2nd, unsigned long frame_pointer) >> +{ >> + return __ftrace_return_to_handler(retval_1st, retval_2nd, frame_pointer); >> +} >> +#else >> +unsigned long ftrace_return_to_handler(unsigned long frame_pointer) >> +{ >> + return __ftrace_return_to_handler(0, 0, frame_pointer); >> +} >> +#endif >> + > > Hi, > > To echo Mark's criticism, I also don't like this. I feel it would be > better if ftrace_return_to_handler() always took the same arguments > irrespective of the setting of CONFIG_FUNCTION_GRAPH_RETVAL. > > On 32-bit ARM, we have to stack r0-r3 anyway to prevent the call to > ftrace_return_to_handler() corrupting the return value, and these > are the registers we need. So we might as well pass a pointer to > these stacked registers. Whether that's acceptable on other > architectures, I couldn't say. Agree, I think we can introduce a new structure called pt_ret_regs for each relevant architecture. The pt_ret_regs should only contain the return registers and the frame pointer register, for arm, they are r0~r3 and r11.Then we can pass the pointer to the pt_ret_regs to ftrace_return_to_handler. > > Thanks. >