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 <mhiramat@xxxxxxxxxx>
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
