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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 18274C61DA4 for ; Thu, 2 Feb 2023 16:57:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232356AbjBBQ5G (ORCPT ); Thu, 2 Feb 2023 11:57:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33444 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229881AbjBBQ5E (ORCPT ); Thu, 2 Feb 2023 11:57:04 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id E78646FD33; Thu, 2 Feb 2023 08:57:02 -0800 (PST) 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 A6999C14; Thu, 2 Feb 2023 08:57:44 -0800 (PST) Received: from FVFF77S0Q05N.cambridge.arm.com (FVFF77S0Q05N.cambridge.arm.com [10.1.27.141]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8E0FC3F64C; Thu, 2 Feb 2023 08:57:00 -0800 (PST) Date: Thu, 2 Feb 2023 16:56:57 +0000 From: Mark Rutland To: Florent Revest Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org, rostedt@goodmis.org, mhiramat@kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, kpsingh@kernel.org, jolsa@kernel.org, xukuohai@huaweicloud.com Subject: Re: [PATCH 5/8] ftrace: Make DIRECT_CALLS work WITH_ARGS and !WITH_REGS Message-ID: References: <20230201163420.1579014-1-revest@chromium.org> <20230201163420.1579014-6-revest@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 02, 2023 at 03:54:33PM +0000, Mark Rutland wrote: > On Wed, Feb 01, 2023 at 05:34:17PM +0100, Florent Revest wrote: > > -#define MULTI_FLAGS (FTRACE_OPS_FL_DIRECT | FTRACE_OPS_FL_SAVE_REGS) > > +#define MULTI_FLAGS (FTRACE_OPS_FL_DIRECT) > > Unfortunately, I think this is broken for architectures where: > > * DYNAMIC_FTRACE_WITH_DIRECT_CALLS=y > * DYNAMIC_FTRACE_WITH_REGS=y > * DYNAMIC_FTRACE_WITH_ARGS=n > > ... since those might pass a NULL ftrace_regs around, and so when using the > list ops arch_ftrace_set_direct_caller() might blow up accessing an element of > ftrace_regs. > > It looks like 32-bit x86 is the only case with that combination, and its > ftrace_caller implementation passes a NULL regs, so I reckon that'll blow up. > However, it looks like there aren't any FTRACE_DIRECT samples wired up for > 32-bit x86, so I'm not aware of a test case we can use. FWIW, the FTRACE_STARTUP_TEST tickles this: [ 1.896209] Testing tracer function_graph: [ 2.900282] BUG: kernel NULL pointer dereference, address: 0000002c [ 2.901171] #PF: supervisor write access in kernel mode [ 2.901171] #PF: error_code(0x0002) - not-present page [ 2.901171] *pde = 00000000 [ 2.901171] Oops: 0002 [#1] PREEMPT SMP [ 2.901171] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.2.0-rc3-00014-gcfd6340c71ce #1 [ 2.901171] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014 [ 2.901171] EIP: call_direct_funcs+0xd/0x1c [ 2.901171] Code: 00 00 00 00 90 a9 00 00 00 01 0f 84 d7 fe ff ff 0d 00 00 80 00 89 46 04 e9 d2 fe ff ff 8b 41 64 85 c0 74 11 55 89 e5 8b 55 08 <89> 42 2c 5d c3 8d b6 00 00 00 00 c3 8d 76 00 89 c1 89 b [ 2.901171] EAX: cc3620e8 EBX: c1147e44 ECX: c1147e44 EDX: 00000000 [ 2.901171] ESI: fffffeff EDI: cc354208 EBP: c1147dbc ESP: c1147dbc [ 2.901171] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00010286 [ 2.901171] CR0: 80050033 CR2: 0000002c CR3: 0d703000 CR4: 00350ed0 [ 2.901171] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000 [ 2.901171] DR6: fffe0ff0 DR7: 00000400 [ 2.901171] Call Trace: [ 2.901171] arch_ftrace_ops_list_func+0xf5/0x1bc [ 2.901171] ? ftrace_enable_ftrace_graph_caller+0x3b/0x44 [ 2.901171] ? trace_selftest_startup_function_graph+0x1d9/0x298 [ 2.901171] ? syscall_unregfunc+0xa0/0xa0 [ 2.901171] ftrace_call+0x5/0x13 [ 2.901171] trace_selftest_dynamic_test_func+0x5/0xc [ 2.901171] trace_selftest_startup_function_graph+0x1d9/0x298 [ 2.901171] ? trace_selftest_dynamic_test_func+0x5/0xc [ 2.901171] ? trace_selftest_startup_function_graph+0x1d9/0x298 [ 2.901171] ? ftrace_check_record+0x340/0x340 [ 2.901171] ? ftrace_check_record+0x340/0x340 [ 2.901171] ? ftrace_stub_graph+0x4/0x4 [ 2.901171] ? trace_selftest_test_regs_func+0x18/0x18 [ 2.901171] run_tracer_selftest+0x7d/0x1bc [ 2.901171] ? graph_depth_read+0x90/0x90 [ 2.901171] register_tracer+0xd3/0x284 [ 2.901171] ? register_trace_event+0xf6/0x180 [ 2.901171] ? init_graph_tracefs+0x38/0x38 [ 2.901171] init_graph_trace+0x56/0x78 [ 2.901171] do_one_initcall+0x53/0x204 [ 2.901171] ? parse_args+0x143/0x3ec [ 2.901171] ? __kmem_cache_alloc_node+0x2d/0x224 [ 2.901171] kernel_init_freeable+0x198/0x2bc [ 2.901171] ? rdinit_setup+0x30/0x30 [ 2.901171] ? rest_init+0xb0/0xb0 [ 2.901171] kernel_init+0x1a/0x1d0 [ 2.901171] ? schedule_tail_wrapper+0x9/0xc [ 2.901171] ret_from_fork+0x1c/0x28 [ 2.901171] Modules linked in: [ 2.901171] CR2: 000000000000002c [ 2.901171] ---[ end trace 0000000000000000 ]--- [ 2.901171] EIP: call_direct_funcs+0xd/0x1c [ 2.901171] Code: 00 00 00 00 90 a9 00 00 00 01 0f 84 d7 fe ff ff 0d 00 00 80 00 89 46 04 e9 d2 fe ff ff 8b 41 64 85 c0 74 11 55 89 e5 8b 55 08 <89> 42 2c 5d c3 8d b6 00 00 00 00 c3 8d 76 00 89 c1 89 b [ 2.901171] EAX: cc3620e8 EBX: c1147e44 ECX: c1147e44 EDX: 00000000 [ 2.901171] ESI: fffffeff EDI: cc354208 EBP: c1147dbc ESP: c1147dbc [ 2.901171] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00010286 [ 2.901171] CR0: 80050033 CR2: 0000002c CR3: 0d703000 CR4: 00350ed0 [ 2.901171] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000 [ 2.901171] DR6: fffe0ff0 DR7: 00000400 [ 2.901171] note: swapper/0[1] exited with preempt_count 1 [ 2.901175] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 [ 2.902171] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 ]--- The below diff solved that for me. Thanks, Mark. ---->8---- diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 84f717f8959e..3d2156e335d7 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -241,6 +241,12 @@ enum { FTRACE_OPS_FL_DIRECT = BIT(17), }; +#ifndef CONFIG_DYNAMIC_FTRACE_WITH_ARGS +#define FTRACE_OPS_FL_SAVE_ARGS FTRACE_OPS_FL_SAVE_REGS +#else +#define FTRACE_OPS_FL_SAVE_ARGS 0 +#endif + /* * FTRACE_OPS_CMD_* commands allow the ftrace core logic to request changes * to a ftrace_ops. Note, the requests may fail. diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 73b6f6489ba1..8e739303b6a2 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5282,7 +5282,7 @@ static LIST_HEAD(ftrace_direct_funcs); static int register_ftrace_function_nolock(struct ftrace_ops *ops); -#define MULTI_FLAGS (FTRACE_OPS_FL_DIRECT) +#define MULTI_FLAGS (FTRACE_OPS_FL_DIRECT | FTRACE_OPS_FL_SAVE_ARGS) static int check_direct_multi(struct ftrace_ops *ops) {