Comment 3 for bug 1855668

------- Comment From <email address hidden> 2020-01-09 00:14 EDT-------
Hi,

Apologies for the delay.

I installed the most recent kernel, modules and extra modules I could find from that PPA on a p8 kvm guest.

dja@dja-guest:~$ uname -a
Linux dja-guest 5.4.0-9-generic #12-Ubuntu SMP Mon Dec 16 22:32:07 UTC 2019 ppc64le ppc64le ppc64le GNU/Linux

The kernel boots fine with no additional command line options, but if booted with lockdown=confidentiality, it has a lot of issues.

Firstly, there are a flood of lines like

[ 0.265197] Could not create tracefs 'set_ftrace_pid' entry
[ 0.265247] Lockdown: swapper/0: use of tracefs is restricted; see man kernel_lockdown.7

for various tracefs entries

Then there are 2 splats:

[ 0.265868] Could not create tracefs 'set_graph_function' entry
[ 0.265931] Lockdown: swapper/0: use of tracefs is restricted; see man kernel_lockdown.7
[ 0.266005] Could not create tracefs 'set_graph_notrace' entry
[ 0.266070] Lockdown: swapper/0: use of tracefs is restricted; see man kernel_lockdown.7
[ 0.266145] ------------[ cut here ]------------
[ 0.266195] Could not register function stat for cpu 0
[ 0.266255] WARNING: CPU: 5 PID: 1 at kernel/trace/ftrace.c:987 ftrace_init_tracefs_toplevel+0x1e8/0x264
[ 0.266342] Modules linked in:
[ 0.266384] CPU: 5 PID: 1 Comm: swapper/0 Not tainted 5.4.0-9-generic #12-Ubuntu
[ 0.266458] NIP: c000000001363430 LR: c00000000136342c CTR: c00000003fff8a00
[ 0.266532] REGS: c0000003fa67f890 TRAP: 0700 Not tainted (5.4.0-9-generic)
[ 0.266612] MSR: 8000000000029033 <SF,EE,ME,IR,DR,RI,LE> CR: 28000244 XER: 20000000
[ 0.266694] CFAR: c00000000013aa5c IRQMASK: 0
GPR00: c00000000136342c c0000003fa67fb20 c000000001a4bb00 000000000000002a
GPR04: 0000000000000001 0000000000000000 00000000000002ca 300d0a7374617420
GPR08: 00000003fbeb0000 c0000000018e3248 c0000000018e3248 c0000000011a3048
GPR12: 0000000000000000 c00000003fff8a00 c0000000000106c0 0000000000000000
GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR24: c0000000011afd48 c000000001a821e0 c0000000019e6f90 c000000001464300
GPR28: c0000003f78fe910 0000000000000000 0000000000000000 c0000003fce14300
[ 0.267313] NIP [c000000001363430] ftrace_init_tracefs_toplevel+0x1e8/0x264
[ 0.267376] LR [c00000000136342c] ftrace_init_tracefs_toplevel+0x1e4/0x264
[ 0.267439] Call Trace:
[ 0.267465] [c0000003fa67fb20] [c00000000136342c] ftrace_init_tracefs_toplevel+0x1e4/0x264 (unreliable)
[ 0.267554] [c0000003fa67fbc0] [c00000000136408c] tracer_init_tracefs+0x100/0x270
[ 0.267632] [c0000003fa67fc10] [c000000000010144] do_one_initcall+0x64/0x2b0
[ 0.267707] [c0000003fa67fce0] [c000000001334694] kernel_init_freeable+0x29c/0x3a0
[ 0.267783] [c0000003fa67fdb0] [c0000000000106dc] kernel_init+0x24/0x148
[ 0.267846] [c0000003fa67fe20] [c00000000000b648] ret_from_kernel_thread+0x5c/0x74
[ 0.267921] Instruction dump:
[ 0.267961] f95f0048 f93f0050 fb830000 4af4eced 60000000 2c230000 4182ff30 3c62ff76
[ 0.268038] 7fa4eb78 38634288 4add75cd 60000000 <0fe00000> 7f83e378 4b0c08f1 60000000
[ 0.268119] ---[ end trace fd202afb6f2e24ec ]---
[ 0.268170] Lockdown: swapper/0: use of tracefs is restricted; see man kernel_lockdown.7
[ 0.268245] Could not create tracefs 'tracing_thresh' entry
[ 0.268295] Lockdown: swapper/0: use of tracefs is restricted; see man kernel_lockdown.7
[ 0.268369] Could not create tracefs 'README' entry
[ 0.268420] Lockdown: swapper/0: use of tracefs is restricted; see man kernel_lockdown.7
[ 0.268493] Could not create tracefs 'saved_cmdlines' entry
[ 0.268544] Lockdown: swapper/0: use of tracefs is restricted; see man kernel_lockdown.7
[ 0.268619] Could not create tracefs 'saved_cmdlines_size' entry
[ 0.268681] Lockdown: swapper/0: use of tracefs is restricted; see man kernel_lockdown.7
[ 0.268756] Could not create tracefs 'saved_tgids' entry
[ 0.271956] Lockdown: swapper/0: use of tracefs is restricted; see man kernel_lockdown.7
[ 0.272038] Could not create tracefs 'dyn_ftrace_total_info' entry
[ 0.272102] Lockdown: swapper/0: use of tracefs is restricted; see man kernel_lockdown.7
[ 0.272178] Could not create tracefs 'funcgraph-overrun' entry
[ 0.272241] ------------[ cut here ]------------
[ 0.272292] Failed to create trace option: funcgraph-overrun
[ 0.272297] WARNING: CPU: 5 PID: 1 at kernel/trace/trace.c:8106 create_trace_option_files+0x2f0/0x330
[ 0.272446] Modules linked in:
[ 0.272484] CPU: 5 PID: 1 Comm: swapper/0 Tainted: G W 5.4.0-9-generic #12-Ubuntu
[ 0.272573] NIP: c0000000002acf90 LR: c0000000002acf8c CTR: 00000000ffffffee
[ 0.272647] REGS: c0000003fa67f840 TRAP: 0700 Tainted: G W (5.4.0-9-generic)
[ 0.272734] MSR: 8000000000029033 <SF,EE,ME,IR,DR,RI,LE> CR: 28000280 XER: 20000000
[ 0.272812] CFAR: c00000000013aa5c IRQMASK: 0
GPR00: c0000000002acf8c c0000003fa67fad0 c000000001a4bb00 0000000000000030
GPR04: c000000001b75660 0000000000000000 6e75727265766f2d 6f20656361727420
GPR08: 00000003fbeb0000 0000000000000000 0000000000000000 c0000000011a3048
GPR12: 0000000000000000 c00000003fff8a00 c0000000000106c0 0000000000000000
GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR20: c0000000019e78e8 0000000000000001 c0000000011b1140 c000000001990345
GPR24: c0000003f78d5800 c0000003f78d5800 0000000000000000 c000000001905ff8
GPR28: c000000001905ff8 0000000000000000 c000000001905fc0 c000000001903998
[ 0.273435] NIP [c0000000002acf90] create_trace_option_files+0x2f0/0x330
[ 0.273498] LR [c0000000002acf8c] create_trace_option_files+0x2ec/0x330
[ 0.273562] Call Trace:
[ 0.273590] [c0000003fa67fad0] [c0000000002acf8c] create_trace_option_files+0x2ec/0x330 (unreliable)
[ 0.273677] [c0000003fa67fb90] [c0000000002ad018] __update_tracer_options+0x48/0x70
[ 0.273754] [c0000003fa67fbc0] [c0000000013641c8] tracer_init_tracefs+0x23c/0x270
[ 0.273828] [c0000003fa67fc10] [c000000000010144] do_one_initcall+0x64/0x2b0
[ 0.273903] [c0000003fa67fce0] [c000000001334694] kernel_init_freeable+0x29c/0x3a0
[ 0.273980] [c0000003fa67fdb0] [c0000000000106dc] kernel_init+0x24/0x148
[ 0.274044] [c0000003fa67fe20] [c00000000000b648] ret_from_kernel_thread+0x5c/0x74
[ 0.274120] Instruction dump:
[ 0.274158] 382100c0 eba1ffe8 7c0803a6 4e800020 89370001 2c090000 4082ff64 e89b0000
[ 0.274234] 7ec3b378 9ab70001 4be8da6d 60000000 <0fe00000> 4bffff48 7f03c378 48176d8d
[ 0.274311] ---[ end trace fd202afb6f2e24ed ]---

I will attach a full dmesg once I figure out how to work the bugzilla bridge.

Kind regards,
Daniel