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Mon, 19 Apr 2021 13:08:18 +0000 Received: from [10.26.49.10] (172.20.145.6) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Mon, 19 Apr 2021 13:08:16 +0000 Subject: Re: [PATCH v3 1/3] tracing: Show real address for trace event arguments To: Masami Hiramatsu , LKML CC: Steven Rostedt , Ingo Molnar , linux-tegra References: <160277369795.29307.6792451054602907237.stgit@devnote2> <160277370703.29307.5134475491761971203.stgit@devnote2> From: Jon Hunter Message-ID: <9835d9f1-8d3a-3440-c53f-516c2606ad07@nvidia.com> Date: Mon, 19 Apr 2021 14:08:14 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <160277370703.29307.5134475491761971203.stgit@devnote2> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [172.20.145.6] X-ClientProxiedBy: HQMAIL105.nvidia.com (172.20.187.12) To HQMAIL107.nvidia.com (172.20.187.13) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 63bccc92-e63d-4a45-d649-08d903343357 X-MS-TrafficTypeDiagnostic: BYAPR12MB2773: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:2733; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Apr 2021 13:08:18.2743 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 63bccc92-e63d-4a45-d649-08d903343357 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.112.34];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CO1NAM11FT008.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR12MB2773 Precedence: bulk List-ID: X-Mailing-List: linux-tegra@vger.kernel.org On 15/10/2020 15:55, Masami Hiramatsu wrote: > To help debugging kernel, show real address for trace event arguments > in tracefs/trace{,pipe} instead of hashed pointer value. > > Since ftrace human-readable format uses vsprintf(), all %p are > translated to hash values instead of pointer address. > > However, when debugging the kernel, raw address value gives a > hint when comparing with the memory mapping in the kernel. > (Those are sometimes used with crash log, which is not hashed too) > So converting %p with %px when calling trace_seq_printf(). > > Moreover, this is not improving the security because the tracefs > can be used only by root user and the raw address values are readable > from tracefs/percpu/cpu*/trace_pipe_raw file. > > Signed-off-by: Masami Hiramatsu I have encountered the following crash on a couple of our ARM64 Jetson platforms and bisect is pointing to this change. The crash I am seeing is on boot when I am directing the trace prints to the console by adding 'tp_printk trace_event="cpu_frequency,cpu_frequency_limits"' to the kernel command line and enabling CONFIG_BOOTTIME_TRACING. Reverting this change does fix the problem. Let me know if you have any thoughts. [ 5.731301] Unable to handle kernel paging request at virtual address fbf80000800040f8 [ 5.739215] Mem abort info: [ 5.742004] ESR = 0x96000004 [ 5.745054] EC = 0x25: DABT (current EL), IL = 32 bits [ 5.750359] SET = 0, FnV = 0 [ 5.753408] EA = 0, S1PTW = 0 [ 5.756543] Data abort info: [ 5.759416] ISV = 0, ISS = 0x00000004 [ 5.763244] CM = 0, WnR = 0 [ 5.766205] [fbf80000800040f8] address between user and kernel address ranges [ 5.773332] Internal error: Oops: 96000004 [#1] PREEMPT SMP [ 5.778898] Modules linked in: [ 5.781952] CPU: 5 PID: 44 Comm: kworker/5:1 Tainted: G S 5.12.0-rc8 #1 [ 5.789861] Hardware name: NVIDIA Jetson TX2 Developer Kit (DT) [ 5.795773] Workqueue: events deferred_probe_work_func [ 5.800913] pstate: 60000085 (nZCv daIf -PAN -UAO -TCO BTYPE=--) [ 5.806911] pc : trace_event_format+0x28/0x1a0 [ 5.811353] lr : trace_event_printf+0x50/0x98 [ 5.815706] sp : ffff80001230b760 [ 5.819014] x29: ffff80001230b760 x28: ffff800011e99c10 [ 5.824324] x27: ffff000082d9ce18 x26: ffff8000115abd30 [ 5.829630] x25: 0000000000000000 x24: ffff800011f3e040 [ 5.834937] x23: ffff0000800050c8 x22: ffff000080004000 [ 5.840242] x21: ffff800012276e38 x20: ffff000080004000 [ 5.845549] x19: ffff800011e99948 x18: ffffffffffffffff [ 5.850854] x17: 0000000000000007 x16: 0000000000000001 [ 5.856161] x15: ffff800011e99948 x14: ffff000082d15688 [ 5.861468] x13: ffff000082d15687 x12: 0000000000000018 [ 5.866774] x11: 0101010101010101 x10: 7f7f7f7f7f7f7f7f [ 5.872082] x9 : 0000000000000090 x8 : 0000000000000095 [ 5.877389] x7 : 0000000000000014 x6 : ffff0000800050de [ 5.882695] x5 : 0000000000000000 x4 : 0000000000000000 [ 5.888002] x3 : ffff80001230b820 x2 : 00000000ffffffd0 [ 5.893308] x1 : ffff8000115abd30 x0 : fbf8000080004080 [ 5.898615] Call trace: [ 5.901056] trace_event_format+0x28/0x1a0 [ 5.905147] trace_event_printf+0x50/0x98 [ 5.909151] trace_raw_output_cpu_frequency_limits+0x48/0x60 [ 5.914807] trace_event_buffer_commit+0x1bc/0x288 [ 5.919592] trace_event_raw_event_cpu_frequency_limits+0x78/0xd0 [ 5.925679] __traceiter_cpu_frequency_limits+0x30/0x48 [ 5.930899] cpufreq_set_policy+0x15c/0x288 [ 5.935079] cpufreq_online+0x6f4/0x928 [ 5.938910] cpufreq_add_dev+0x78/0x88 [ 5.942654] subsys_interface_register+0x9c/0xf0 [ 5.947266] cpufreq_register_driver+0x170/0x218 [ 5.951878] tegra186_cpufreq_probe+0x164/0x350 [ 5.956404] platform_probe+0x90/0xd8 [ 5.960061] really_probe+0x20c/0x3e8 [ 5.963720] driver_probe_device+0x54/0xb8 [ 5.967812] __device_attach_driver+0x90/0xc0 [ 5.972161] bus_for_each_drv+0x70/0xc8 [ 5.975992] __device_attach+0xec/0x150 [ 5.979825] device_initial_probe+0x10/0x18 [ 5.984002] bus_probe_device+0x94/0xa0 [ 5.987833] deferred_probe_work_func+0x80/0xb8 [ 5.992359] process_one_work+0x1f0/0x4b8 [ 5.996368] worker_thread+0x20c/0x450 [ 6.000112] kthread+0x124/0x150 [ 6.003337] ret_from_fork+0x10/0x18 [ 6.006913] Code: b4000b21 aa0003f6 f9400000 aa0103fa (b9407800) [ 6.013000] ---[ end trace eae1531f47c7c14a ]--- Thanks! Jon -- nvpublic