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 09551C433F5 for ; Tue, 30 Nov 2021 15:26:24 +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=I8FuN4RaYxaFg2n/bkw2/Ocgmsfi77VLllKKW6aikT0=; b=CwNlm1/f7YuENr wfzfMMnMTUiwR0ts5flaDpYHWpeML3M0YEfoD7PqIjxIl+KTM6pC09j/0MTdH3000ZrT5FEzkHTBW I6mGwExb7SSP+TGkHA7zhJgzppMbMoXr6JmN3HGG2I9RJGuCgTFoz2s1s9uI8Z/5j01S5FZK7w8A8 oH0Mrsy+/yVGr8epotDwKnz60CvE6Ki3mhGfcT6btKndewqOuh+wCnwLKg3Xcwv+k47j2c6ISFDhb BbUDPl7JLgxsbBwLYIg9vxWuyTsxNZwdLk3cbMMX1gUOg9Cf7fi9e9Q2yUaip7EfQdSNBI54PGQhg qd836buXlK6Vl9acFOCw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ms4zM-005sGm-LS; Tue, 30 Nov 2021 15:24:14 +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 1ms4ho-005mwV-SS for linux-arm-kernel@lists.infradead.org; Tue, 30 Nov 2021 15:06:09 +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 E1E9B1063; Tue, 30 Nov 2021 07:06:00 -0800 (PST) Received: from FVFF77S0Q05N (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AFFC83F5A1; Tue, 30 Nov 2021 07:05:58 -0800 (PST) Date: Tue, 30 Nov 2021 15:05:48 +0000 From: Mark Rutland To: madvenka@linux.microsoft.com Cc: broonie@kernel.org, jpoimboe@redhat.com, ardb@kernel.org, nobuta.keiya@fujitsu.com, sjitindarsingh@gmail.com, catalin.marinas@arm.com, will@kernel.org, jmorris@namei.org, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v11 1/5] arm64: Call stack_backtrace() only from within walk_stackframe() Message-ID: References: <8b861784d85a21a9bf08598938c11aff1b1249b9> <20211123193723.12112-1-madvenka@linux.microsoft.com> <20211123193723.12112-2-madvenka@linux.microsoft.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20211123193723.12112-2-madvenka@linux.microsoft.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211130_070605_061303_B5A11E87 X-CRM114-Status: GOOD ( 24.77 ) 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 Tue, Nov 23, 2021 at 01:37:19PM -0600, madvenka@linux.microsoft.com wrote: > From: "Madhavan T. Venkataraman" > > Currently, arch_stack_walk() calls start_backtrace() and walk_stackframe() > separately. There is no need to do that. Instead, call start_backtrace() > from within walk_stackframe(). In other words, walk_stackframe() is the only > unwind function a consumer needs to call. > > Currently, the only consumer is arch_stack_walk(). In the future, > arch_stack_walk_reliable() will be another consumer. > > Currently, there is a check for a NULL task in unwind_frame(). It is not > needed since all current consumers pass a non-NULL task. Can you split the NULL check change into a preparatory patch? That change is fine in isolation (and easier to review/ack), and it's nicer for future bisection to not group that with unrelated changes. > Use struct stackframe only within the unwind functions. > > Signed-off-by: Madhavan T. Venkataraman > --- > arch/arm64/kernel/stacktrace.c | 41 ++++++++++++++++++---------------- > 1 file changed, 22 insertions(+), 19 deletions(-) > > diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c > index 0fb58fed54cb..7217c4f63ef7 100644 > --- a/arch/arm64/kernel/stacktrace.c > +++ b/arch/arm64/kernel/stacktrace.c > @@ -69,9 +69,6 @@ static int notrace unwind_frame(struct task_struct *tsk, > unsigned long fp = frame->fp; > struct stack_info info; > > - if (!tsk) > - tsk = current; > - > /* Final frame; nothing to unwind */ > if (fp == (unsigned long)task_pt_regs(tsk)->stackframe) > return -ENOENT; > @@ -143,15 +140,19 @@ static int notrace unwind_frame(struct task_struct *tsk, > NOKPROBE_SYMBOL(unwind_frame); > > static void notrace walk_stackframe(struct task_struct *tsk, > - struct stackframe *frame, > + unsigned long fp, unsigned long pc, > bool (*fn)(void *, unsigned long), void *data) > { > + struct stackframe frame; > + > + start_backtrace(&frame, fp, pc); > + > while (1) { > int ret; > > - if (!fn(data, frame->pc)) > + if (!fn(data, frame.pc)) > break; > - ret = unwind_frame(tsk, frame); > + ret = unwind_frame(tsk, &frame); > if (ret < 0) > break; > } > @@ -195,17 +196,19 @@ noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry, > void *cookie, struct task_struct *task, > struct pt_regs *regs) > { > - struct stackframe frame; > - > - if (regs) > - start_backtrace(&frame, regs->regs[29], regs->pc); > - else if (task == current) > - start_backtrace(&frame, > - (unsigned long)__builtin_frame_address(1), > - (unsigned long)__builtin_return_address(0)); > - else > - start_backtrace(&frame, thread_saved_fp(task), > - thread_saved_pc(task)); > - > - walk_stackframe(task, &frame, consume_entry, cookie); > + unsigned long fp, pc; > + > + if (regs) { > + fp = regs->regs[29]; > + pc = regs->pc; > + } else if (task == current) { > + /* Skip arch_stack_walk() in the stack trace. */ > + fp = (unsigned long)__builtin_frame_address(1); > + pc = (unsigned long)__builtin_return_address(0); > + } else { > + /* Caller guarantees that the task is not running. */ > + fp = thread_saved_fp(task); > + pc = thread_saved_pc(task); > + } > + walk_stackframe(task, fp, pc, consume_entry, cookie); I'd prefer to leave this as-is. The new and old structure are largely equivalent, so we haven't made this any simpler, but we have added more arguments to walk_stackframe(). One thing I *would* like to do is move tsk into strcut stackframe, so we only need to pass that around, which'll make it easier to refactor the core unwind logic. Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel