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 01695C27C4F for ; Tue, 18 Jun 2024 16:50:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To: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=8Rj2egRUPIqs2wPGBjJ3mHoRYj3Hi5qo8zfXUT0EKek=; b=YMvfH7XcEEHp7b5KY7LDgmP/dY xtk6jQYlb0dNwXL6JLbtcdIBZd0a6DsquCVDU1VR/NRvzOoS2mjXhKdae/eM3A2aAQ3kkF182ddoF H3Y/0z0OkDsnKjCOykBmK3HDptFSqV8vuiyiG35rYqwjxoaceCzMDP9jBYlS0QLIr3QhCo1+AtIBm yufHcnvOFoqr7R7S9+DsSUduLIFcLWkJF/CEW0ZahyYLvshy5kKD7AzdnjeC0uA6uGfa8h30JTlXN nP0B2zF3/HzAitJfnGPYmdbuaKULsBwE8TUi6wesPEn9ohxIYoEJuhzz7jvKV8lRpIXwYPocl1YLN bdvDmyqA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sJc2c-0000000FvQy-0pgI; Tue, 18 Jun 2024 16:50:42 +0000 Received: from sin.source.kernel.org ([2604:1380:40e1:4800::1]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sJc2Z-0000000FvQ1-0yk2 for linux-arm-kernel@lists.infradead.org; Tue, 18 Jun 2024 16:50:41 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id BDD80CE0E64; Tue, 18 Jun 2024 16:50:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A2FC9C3277B; Tue, 18 Jun 2024 16:50:32 +0000 (UTC) Date: Tue, 18 Jun 2024 12:50:31 -0400 From: Steven Rostedt To: Puranjay Mohan Cc: Catalin Marinas , Will Deacon , Mark Rutland , "Madhavan T. Venkataraman" , Kalesh Singh , chenqiwu , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, puranjay12@gmail.com Subject: Re: [PATCH] arm64: stacktrace: fix the usage of ftrace_graph_ret_addr() Message-ID: <20240618125031.22642d40@rorschach.local.home> In-Reply-To: <20240618162342.28275-1-puranjay@kernel.org> References: <20240618162342.28275-1-puranjay@kernel.org> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240618_095039_513923_0DAC2DAB X-CRM114-Status: GOOD ( 23.47 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 18 Jun 2024 16:23:42 +0000 Puranjay Mohan wrote: > ftrace_graph_ret_addr() takes an 'idx' integer pointer that is used to > optimize the stack unwinding process. arm64 currently passes `NULL` for > this parameter which stops it from utilizing these optimizations. It no longer is an optimization (in linux-next). If it's not included, it doesn't bother to find what the "return_to_handler" actually points to. > > Further, the current code for ftrace_graph_ret_addr() will just return > the passed in return address if it is NULL which will break this usage. > > Pass a valid integer pointer to ftrace_graph_ret_addr() similar to > x86_64's stack unwinder. In the next merge window, this will not work. Besides the comment about "optimization" not the real reason for this change... Reviewed-by: Steven Rostedt (Google) -- Steve > > Signed-off-by: Puranjay Mohan > --- > arch/arm64/kernel/stacktrace.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c > index 6b3258860377..2729faaee4b4 100644 > --- a/arch/arm64/kernel/stacktrace.c > +++ b/arch/arm64/kernel/stacktrace.c > @@ -25,6 +25,7 @@ > * > * @common: Common unwind state. > * @task: The task being unwound. > + * @graph_idx: Used by ftrace_graph_ret_addr() for optimized stack unwinding. > * @kr_cur: When KRETPROBES is selected, holds the kretprobe instance > * associated with the most recently encountered replacement lr > * value. > @@ -32,6 +33,7 @@ > struct kunwind_state { > struct unwind_state common; > struct task_struct *task; > + int graph_idx; > #ifdef CONFIG_KRETPROBES > struct llist_node *kr_cur; > #endif > @@ -106,7 +108,7 @@ kunwind_recover_return_address(struct kunwind_state *state) > if (state->task->ret_stack && > (state->common.pc == (unsigned long)return_to_handler)) { > unsigned long orig_pc; > - orig_pc = ftrace_graph_ret_addr(state->task, NULL, > + orig_pc = ftrace_graph_ret_addr(state->task, &state->graph_idx, > state->common.pc, > (void *)state->common.fp); > if (WARN_ON_ONCE(state->common.pc == orig_pc))