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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7645DC433F5 for ; Tue, 19 Apr 2022 13:47:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=d9H3p+OmaZF3FkC6fTApFuFrKIni5zQTKm5QBL6CJ7Y=; b=h6Da5HvtfU+ZHx 3dbmkkyIZFTpwxqflu35xg736vxX4YmKNE5sxPjMnrIYys2hQ36AM3QXcbWIGItOzjffzU+TLjFVN mRr3I75BpjHbx0K58TxzU0azYP6yTWt8rwMcp3xd43L6W9eQzC7rTGbApecxJLuZ723WZhOCxaGN3 CKme61e/8pj78nKfjhXHgczLHPOBWGX/0ZhRt6bDm3ITXyTtSpfnZgHaSOaYiHpIfEg6AdQBxFNdG LkCtCfS8ma0bIgIAgRkudpGODx4OtFWZRo2Hgtlm+gVswVEVRgoHRLCRNXgG8Uu9aGX1pSdrFH7A3 dmBbi46DfwY6kWBcQpfQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ngoAg-003yQK-R6; Tue, 19 Apr 2022 13:45:35 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ngnOB-003e5u-Ic for linux-arm-kernel@lists.infradead.org; Tue, 19 Apr 2022 12:55:29 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4DB62106F; Tue, 19 Apr 2022 05:55:26 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [10.57.75.72]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D6A513F766; Tue, 19 Apr 2022 05:55:23 -0700 (PDT) Date: Tue, 19 Apr 2022 13:55:19 +0100 From: Mark Rutland To: Chengming Zhou Cc: rostedt@goodmis.org, mingo@redhat.com, catalin.marinas@arm.com, will@kernel.org, tglx@linutronix.de, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, broonie@kernel.org, ardb@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, duanxiongchun@bytedance.com, songmuchun@bytedance.com Subject: Re: [PATCH v4 2/2] arm64/ftrace: Make function graph use ftrace directly Message-ID: References: <20220409153554.14470-1-zhouchengming@bytedance.com> <20220409153554.14470-2-zhouchengming@bytedance.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220409153554.14470-2-zhouchengming@bytedance.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220419_055527_755723_F928EEC2 X-CRM114-Status: GOOD ( 33.89 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Sat, Apr 09, 2022 at 11:35:54PM +0800, Chengming Zhou wrote: > As we do in commit 0c0593b45c9b ("x86/ftrace: Make function graph > use ftrace directly"), we don't need special hook for graph tracer, > but instead we use graph_ops:func function to install return_hooker. > > Since commit 3b23e4991fb6 ("arm64: implement ftrace with regs") add > implementation for FTRACE_WITH_REGS on arm64, we can easily adopt > the same cleanup on arm64. > > And this cleanup only changes the FTRACE_WITH_REGS implementation, > so the mcount-based implementation is unaffected. Could you please say *why* we only do this for FTRACE_WITH_REGS? IIUC that's possible, but would require more invasive refactoring of the core code; have I understood correctly? If so, could we please make this: | While in theory it would be possible to make a similar cleanup for | !FTRACE_WITH_REGS, this will require rework of the core code, and so for now | we only change the FTRACE_WITH_REGS implementation. It'd be quite nice if we could clean up the !FTRACE_WITH_REGS case similarly, but as it appeass that would require far more invasive changes, I'm happy to leave that for future work. > > Signed-off-by: Chengming Zhou > --- > v3: > - Add comments in ftrace_graph_func() as suggested by Steve. Thanks. > > v2: > - Remove FTRACE_WITH_REGS ftrace_graph_caller asm, thanks Mark. > --- > arch/arm64/include/asm/ftrace.h | 7 +++++++ > arch/arm64/kernel/entry-ftrace.S | 17 ----------------- > arch/arm64/kernel/ftrace.c | 17 +++++++++++++++++ > 3 files changed, 24 insertions(+), 17 deletions(-) > > diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h > index 1494cfa8639b..dbc45a4157fa 100644 > --- a/arch/arm64/include/asm/ftrace.h > +++ b/arch/arm64/include/asm/ftrace.h > @@ -80,8 +80,15 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr) > > #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > struct dyn_ftrace; > +struct ftrace_ops; > +struct ftrace_regs; > + > int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec); > #define ftrace_init_nop ftrace_init_nop > + > +void ftrace_graph_func(unsigned long ip, unsigned long parent_ip, > + struct ftrace_ops *op, struct ftrace_regs *fregs); > +#define ftrace_graph_func ftrace_graph_func > #endif > > #define ftrace_return_address(n) return_address(n) > diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S > index e535480a4069..d42a205ef625 100644 > --- a/arch/arm64/kernel/entry-ftrace.S > +++ b/arch/arm64/kernel/entry-ftrace.S > @@ -97,12 +97,6 @@ SYM_CODE_START(ftrace_common) > SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL) > bl ftrace_stub > > -#ifdef CONFIG_FUNCTION_GRAPH_TRACER > -SYM_INNER_LABEL(ftrace_graph_call, SYM_L_GLOBAL) // ftrace_graph_caller(); > - nop // If enabled, this will be replaced > - // "b ftrace_graph_caller" > -#endif > - > /* > * At the callsite x0-x8 and x19-x30 were live. Any C code will have preserved > * x19-x29 per the AAPCS, and we created frame records upon entry, so we need > @@ -127,17 +121,6 @@ ftrace_common_return: > ret x9 > SYM_CODE_END(ftrace_common) > > -#ifdef CONFIG_FUNCTION_GRAPH_TRACER > -SYM_CODE_START(ftrace_graph_caller) > - ldr x0, [sp, #S_PC] > - sub x0, x0, #AARCH64_INSN_SIZE // ip (callsite's BL insn) > - add x1, sp, #S_LR // parent_ip (callsite's LR) > - ldr x2, [sp, #PT_REGS_SIZE] // parent fp (callsite's FP) > - bl prepare_ftrace_return > - b ftrace_common_return > -SYM_CODE_END(ftrace_graph_caller) > -#endif > - > #else /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */ > > /* > diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c > index 4506c4a90ac1..35eb7c9b5e53 100644 > --- a/arch/arm64/kernel/ftrace.c > +++ b/arch/arm64/kernel/ftrace.c > @@ -268,6 +268,22 @@ void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent, > } > > #ifdef CONFIG_DYNAMIC_FTRACE > + > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > +void ftrace_graph_func(unsigned long ip, unsigned long parent_ip, > + struct ftrace_ops *op, struct ftrace_regs *fregs) > +{ > + /* > + * Athough graph_ops doesn't have FTRACE_OPS_FL_SAVE_REGS set in flags, > + * regs can't be NULL in DYNAMIC_FTRACE_WITH_REGS. By design, it should > + * be fixed when DYNAMIC_FTRACE_WITH_ARGS is implemented. > + */ This is a bit confusing, since it makes it sound like there's an bug in the current implementation, rather than something that would need to change if support for DYNAMIC_FTRACE_WITH_ARGS is added. Could we please make this: /* * When DYNAMIC_FTRACE_WITH_REGS is selected, `fregs` can never be NULL * and arch_ftrace_get_regs(fregs) will always give a non-NULL pt_regs * in which we can safely modify the LR. */ Other than that, this looks good to me. I gave it a spin under QEMU atop v5.18-rc3. The CONFIG_FTRACE_STARTUP_TEST tests all pass, and I played with the graph tracer with: | # echo do_el0_svc > /sys/kernel/tracing/set_graph_function | # echo function_graph > /sys/kernel/tracing/current_tracer ... for which the resutls looks sane. To make sure this didn't adversely affect the return address rewriting, I also concurrently ran perf with: | # perf record -g -e raw_syscalls:sys_enter:k /bin/true | # perf report ... for which the results also looked fine. I also tested the !DYNAMIC_FTRACE_WITH_REGS modes by building with an older compiler and also building with !DYNAMIC_FTRACE, which all looked good. So FWIW: Tested-by: Mark Rutland ... and if you make the changes I requested above: Reviewed-by: Mark Rutland If you could spin a v5 with that folded in, that would be great. Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel