From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BBA7E20330; Thu, 21 Aug 2025 06:11:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755756717; cv=none; b=P4LQZLiTRrVJgOBqtMabvyBZXrIVTofkdCQ/w24ZS0QeUY3cUrRu85wJNI5eOFsroS+7z3zRjmRKaqTDgSRJEDb4tOW4kteR2WH3up1R6Cu1PX5kTquTfbMlcAPqr2CLH4lnOuB/4TohN56ksQ38ew7isRjZDneO7aLhkKFQzLQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755756717; c=relaxed/simple; bh=+PhorBsR6XMQ86wn4MXz/aLDVw7PeqDWpjqLZ/xx6is=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=RIEah0tHvm98D7pippusqTkVYcbzaMHFUSW/Kc8JCR8RBzSJ8rn9zySpBIkCSpeYZyws+38dLHYxzXKKKQzS526id3N78OZJkAR+vawdiGZ6a9Rcraw56EyUlSpbMK/cehmfYewrVGNxi0wFgBfhyHZFBq0d9wq3jiRFS9wPMOY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=qP+aS7CD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="qP+aS7CD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8D8EFC4CEED; Thu, 21 Aug 2025 06:11:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755756717; bh=+PhorBsR6XMQ86wn4MXz/aLDVw7PeqDWpjqLZ/xx6is=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=qP+aS7CDTcx3AaSCB8aROP8Z3j5y7rpn2d+cQ4/5rom6GopCD2X8201ocHvfjnbPq o/Cqmum51WzIu7FGUPN30V/Q1n6m5dy0uwtUrdhJW1EV/uJuj/LsDDJ2sDRmKQqJo2 CDMaQEuOQUOPifZxG8sSL97Jjg1Azpr1lNncNe8HEw0UAEVpeN7hHxCIuv8ABSHBtf ah/5gVJtO3HEOHaOFnydT/vSubHbRhIUY++u+Vr8YnV3gnCseqsBygmFo/gYGa45bo T7HdPJpFfC9C6URSWpKF+U5IQlLjeZifbgPzsNweYN9q2OxnY1BS8BTLpZ4uV/EAXI AaBmI9I71YYBw== Date: Thu, 21 Aug 2025 09:11:46 +0300 From: Mike Rapoport To: Steven Rostedt Cc: Andrew Morton , Andy Lutomirski , Borislav Petkov , Christophe Leroy , Daniel Gomez , Dave Hansen , Ingo Molnar , "Liam R. Howlett" , Luis Chamberlain , Mark Rutland , Masami Hiramatsu , "H. Peter Anvin" , Peter Zijlstra , Petr Pavlu , Sami Tolvanen , Thomas Gleixner , Yann Ylavic , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-modules@vger.kernel.org, linux-trace-kernel@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH v3 8/8] x86/ftrace: enable EXECMEM_ROX_CACHE for ftrace allocations Message-ID: References: <20250713071730.4117334-1-rppt@kernel.org> <20250713071730.4117334-9-rppt@kernel.org> <20250820184743.0302a8b5@gandalf.local.home> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250820184743.0302a8b5@gandalf.local.home> On Wed, Aug 20, 2025 at 06:47:43PM -0400, Steven Rostedt wrote: > On Sun, 13 Jul 2025 10:17:30 +0300 > Mike Rapoport wrote: > > > From: "Mike Rapoport (Microsoft)" > > > > For the most part ftrace uses text poking and can handle ROX memory. > > The only place that requires writable memory is create_trampoline() that > > updates the allocated memory and in the end makes it ROX. > > > > Use execmem_alloc_rw() in x86::ftrace::alloc_tramp() and enable ROX cache > > for EXECMEM_FTRACE when configuration and CPU features allow that. > > > > Acked-by: Peter Zijlstra (Intel) > > Signed-off-by: Mike Rapoport (Microsoft) > > --- > > The "ftrace=function" kernel command line started crashing with v6.17-rc1, > and I bisected it down to this commit: > > 5d79c2be5081 ("x86/ftrace: enable EXECMEM_ROX_CACHE for ftrace allocations") > > On boot I hit this: > > [ 0.159269] BUG: kernel NULL pointer dereference, address: 000000000000001c > [ 0.160254] #PF: supervisor read access in kernel mode > [ 0.160975] #PF: error_code(0x0000) - not-present page > [ 0.161697] PGD 0 P4D 0 > [ 0.162055] Oops: Oops: 0000 [#1] SMP PTI > [ 0.162619] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.17.0-rc2-test-00006-g48d06e78b7cb-dirty #9 PREEMPT(undef) > [ 0.164141] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 > [ 0.165439] RIP: 0010:kmem_cache_alloc_noprof (mm/slub.c:4237) > [ 0.177483] Call Trace: > [ 0.177828] > [ 0.178123] mas_alloc_nodes (lib/maple_tree.c:176 (discriminator 2) lib/maple_tree.c:1255 (discriminator 2)) > [ 0.178692] mas_store_gfp (lib/maple_tree.c:5468) > [ 0.179223] execmem_cache_add_locked (mm/execmem.c:207) > [ 0.179870] execmem_alloc (mm/execmem.c:213 mm/execmem.c:313 mm/execmem.c:335 mm/execmem.c:475) > [ 0.180397] ? ftrace_caller (arch/x86/kernel/ftrace_64.S:169) > [ 0.180922] ? __pfx_ftrace_caller (arch/x86/kernel/ftrace_64.S:158) > [ 0.181517] execmem_alloc_rw (mm/execmem.c:487) > [ 0.182052] arch_ftrace_update_trampoline (arch/x86/kernel/ftrace.c:266 arch/x86/kernel/ftrace.c:344 arch/x86/kernel/ftrace.c:474) > [ 0.182778] ? ftrace_caller_op_ptr (arch/x86/kernel/ftrace_64.S:182) > [ 0.183388] ftrace_update_trampoline (kernel/trace/ftrace.c:7947) > [ 0.184024] __register_ftrace_function (kernel/trace/ftrace.c:368) > [ 0.184682] ftrace_startup (kernel/trace/ftrace.c:3048) > [ 0.185205] ? __pfx_function_trace_call (kernel/trace/trace_functions.c:210) > [ 0.185877] register_ftrace_function_nolock (kernel/trace/ftrace.c:8717) > [ 0.186595] register_ftrace_function (kernel/trace/ftrace.c:8745) > [ 0.187254] ? __pfx_function_trace_call (kernel/trace/trace_functions.c:210) > [ 0.187924] function_trace_init (kernel/trace/trace_functions.c:170) > [ 0.188499] tracing_set_tracer (kernel/trace/trace.c:5916 kernel/trace/trace.c:6349) > [ 0.189088] register_tracer (kernel/trace/trace.c:2391) > [ 0.189642] early_trace_init (kernel/trace/trace.c:11075 kernel/trace/trace.c:11149) > [ 0.190204] start_kernel (init/main.c:970) > [ 0.190732] x86_64_start_reservations (arch/x86/kernel/head64.c:307) > [ 0.191381] x86_64_start_kernel (??:?) > [ 0.191955] common_startup_64 (arch/x86/kernel/head_64.S:419) > [ 0.192534] > [ 0.192839] Modules linked in: > [ 0.193267] CR2: 000000000000001c > [ 0.193730] ---[ end trace 0000000000000000 ]--- maple tree is initialized after ftrace, so the patch below should fix it: diff --git a/init/main.c b/init/main.c index 0ee0ee7b7c2c..5753e9539ae6 100644 --- a/init/main.c +++ b/init/main.c @@ -956,6 +956,7 @@ void start_kernel(void) sort_main_extable(); trap_init(); mm_core_init(); + maple_tree_init(); poking_init(); ftrace_init(); @@ -973,7 +974,6 @@ void start_kernel(void) "Interrupts were enabled *very* early, fixing it\n")) local_irq_disable(); radix_tree_init(); - maple_tree_init(); /* * Set up housekeeping before setting up workqueues to allow the unbound > -- Steve -- Sincerely yours, Mike.