From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) (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 2FA2B2DC355; Wed, 20 Aug 2025 22:47:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.17 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755730071; cv=none; b=pI8Fn9D0lo4KxwmvMxbHSCl6kMhUKCzXF5/Gp0at8bcTOBjSW8wo/QT16GQPseL1qf+vWUSLSFgSjouyrj1ijTFl1nyJD8v6MxgRs4npcNbrA+DMQkNaf7lOwJQVEnusT81xMmgx75vJ8jJr8gtEftKajaDHxMYG1HXerCnkG60= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755730071; c=relaxed/simple; bh=VA4mP2VLRQz6yfgaKC1bMAw560ME6HO37gLDWWtCaXU=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=AJJrxoDsdkTUx++LypFbFpbGiUlfLGZ2UCq2U8gXtEnJze4GjmvbisKQBsdELF6kv5+1+HkNVC5wojyMV+cRQhHtXJVQVuzYTBXFUPxQprnV1t4owZk21+/uSYuvGHeL88tcuQw8TaBPu+qwqq89nm5Yjya2HnQeNzWz6XXAW2Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.17 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 13F431A01A2; Wed, 20 Aug 2025 22:47:45 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf16.hostedemail.com (Postfix) with ESMTPA id 6CA042000F; Wed, 20 Aug 2025 22:47:40 +0000 (UTC) Date: Wed, 20 Aug 2025 18:47:43 -0400 From: Steven Rostedt To: Mike Rapoport 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: <20250820184743.0302a8b5@gandalf.local.home> In-Reply-To: <20250713071730.4117334-9-rppt@kernel.org> References: <20250713071730.4117334-1-rppt@kernel.org> <20250713071730.4117334-9-rppt@kernel.org> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 6CA042000F X-Stat-Signature: 4rys4zzq3grmk4iz8njd9hcrd1n9a5xk X-Rspamd-Server: rspamout06 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX18niudp8MzlJSk2CKpi7L3PVVfh56aRSjY= X-HE-Tag: 1755730060-24004 X-HE-Meta: U2FsdGVkX185NYSqNdNBNsPuTnEliAO8Pc9z/2zyL0/XZrgDjC2inAGrNVdtT8LaunP4GdSwgzUzAn0ieYTKYrkbJp3U73834SFXYZuN7MPquEyZfj5HnY3VvzSvP8qywLdkkudYQ2iBDo0rKKZ2Z2PvVVo77G5u3qQ6vh4roaJGnq6fG7h4qIt/EcJN4NcwslrDJloAhoMhNTWc/+k0jLFaIT+RUaSQCiHki1SfKSCtJUP9PaWU881E2pAAQo9VoCuEnfmObDwj9kkkLrT0pvuxR9LGxQr4OXtwTYzRILsya/suHDdPWf24wawtOurEPMWbSml/gm4JHnwobNCY2fmluAzlK6zAAAAIwM1AP2VVrDDmRRbVbJ9Nx+QY3dxvRvS3KddU+q5e3ucoNss1rQ== 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) [ 0.166186] Code: 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 55 48 89 e5 41 57 41 56 41 55 41 54 49 89 fc 53 48 83 e4 f0 48 83 ec 20 8b 05 c9 b6 7e 01 <44> 8b 77 1c 65 4c 8b 2d b5 ea 20 02 4c 89 6c 24 18 41 89 f5 21 f0 All code ======== 0: 90 nop 1: 90 nop 2: 90 nop 3: f3 0f 1e fa endbr64 7: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) c: 55 push %rbp d: 48 89 e5 mov %rsp,%rbp 10: 41 57 push %r15 12: 41 56 push %r14 14: 41 55 push %r13 16: 41 54 push %r12 18: 49 89 fc mov %rdi,%r12 1b: 53 push %rbx 1c: 48 83 e4 f0 and $0xfffffffffffffff0,%rsp 20: 48 83 ec 20 sub $0x20,%rsp 24: 8b 05 c9 b6 7e 01 mov 0x17eb6c9(%rip),%eax # 0x17eb6f3 2a:* 44 8b 77 1c mov 0x1c(%rdi),%r14d <-- trapping instruction 2e: 65 4c 8b 2d b5 ea 20 mov %gs:0x220eab5(%rip),%r13 # 0x220eaeb 35: 02 36: 4c 89 6c 24 18 mov %r13,0x18(%rsp) 3b: 41 89 f5 mov %esi,%r13d 3e: 21 f0 and %esi,%eax Code starting with the faulting instruction =========================================== 0: 44 8b 77 1c mov 0x1c(%rdi),%r14d 4: 65 4c 8b 2d b5 ea 20 mov %gs:0x220eab5(%rip),%r13 # 0x220eac1 b: 02 c: 4c 89 6c 24 18 mov %r13,0x18(%rsp) 11: 41 89 f5 mov %esi,%r13d 14: 21 f0 and %esi,%eax [ 0.168811] RSP: 0000:ffffffffb2e03b30 EFLAGS: 00010086 [ 0.169545] RAX: 0000000001fff33f RBX: 0000000000000000 RCX: 0000000000000000 [ 0.170544] RDX: 0000000000002800 RSI: 0000000000002800 RDI: 0000000000000000 [ 0.171554] RBP: ffffffffb2e03b80 R08: 0000000000000004 R09: ffffffffb2e03c90 [ 0.172549] R10: ffffffffb2e03c90 R11: 0000000000000000 R12: 0000000000000000 [ 0.173544] R13: ffffffffb2e03c90 R14: ffffffffb2e03c90 R15: 0000000000000001 [ 0.174542] FS: 0000000000000000(0000) GS:ffff9d2808114000(0000) knlGS:0000000000000000 [ 0.175684] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 0.176486] CR2: 000000000000001c CR3: 000000007264c001 CR4: 00000000000200b0 [ 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 ]--- -- Steve