[BUG][tip] ftrace: mmiotracer hit a bug in mm

[Masami Hiramatsu]

Here is what I've gotten on tip/master (4.2-rc1 base).

I ran the ftracetest and 2nd basic test for tracers hit a bug which completely
freeze the machine (maybe it broke pagetables).
>From the message it happened when initializing kmmio. Without CONFIG_MMIOTRACE
it has gone.

$ sudo ./ftracetest
=== Ftrace unit tests ===
[1] Basic trace file check      [PASS]
[2] Basic test for tracers[  216.878455] ------------[ cut here ]------------
[  216.879905] kernel BUG at /home/mhiramat/ksrc/linux-3/arch/x86/mm/init_64.c:212!
[  216.882022] invalid opcode: 0000 [#1] SMP
[  216.883294] Modules linked in: ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 nf_conntrack_ipv6 nf_defrag_ipv6 ipt_REJECT nf_reject_ipv4 xt_conntrack ebtable_nat ebtable_broute bridge stp llc
ebtable_filter ebtables ip6table_mangle ip6table_security ip6table_raw ip6table_filter ip6_tables iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle
iptable_security iptable_raw iptable_filter ip_tables sg pcspkr acpi_cpufreq dm_mirror dm_region_hash dm_log dm_mod
[  216.897025] CPU: 0 PID: 1322 Comm: ftracetest Not tainted 4.2.0-rc1+ #40
[  216.898944] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
[  216.900615] task: ffff880076e55dc0 ti: ffff880035cdc000 task.ti: ffff880035cdc000
[  216.902760] RIP: 0010:[<ffffffff810b349f>]  [<ffffffff810b349f>] sync_global_pgds+0x18f/0x1a0
[  216.905253] RSP: 0018:ffff880035cdfc58  EFLAGS: 00010287
[  216.906782] RAX: ffff88007d09a000 RBX: ffff88003520ddc0 RCX: ffff880000000000
[  216.908831] RDX: ffff88007909c000 RSI: 000000007d09a067 RDI: 000000007d09a067
[  216.910880] RBP: ffff880035cdfca8 R08: ffff880035cdfc00 R09: 0000000000000002
[  216.912948] R10: 0000000000000004 R11: 0000000000000005 R12: ffff88003520ddc0
[  216.914998] R13: ffff880079094000 R14: ffffffff81b58c90 R15: ffff880076f3da64
[  216.917047] FS:  00007f23c8e82740(0000) GS:ffff88007fc00000(0000) knlGS:0000000000000000
[  216.919372] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[  216.921027] CR2: 000000000078609c CR3: 0000000035cda000 CR4: 00000000000007f0
[  216.923088] Stack:
[  216.923700]  ffffe8ffffffffff ffffc90000000000 ffff88003520e428 0000000088cbb921
[  216.925983]  ffff880035cdfc00 ffffffff81b7fc20 ffff880035cdfd8b ffffffff82057e80
[  216.928273]  000000000000000a 0000000000000000 ffff880035cdfcb8 ffffffff810b5102
[  216.930553] Call Trace:
[  216.931289]  [<ffffffff810b5102>] vmalloc_sync_all+0x22/0x30
[  216.932922]  [<ffffffff810e7556>] register_die_notifier+0x16/0x30
[  216.934702]  [<ffffffff810bcb2f>] kmmio_init+0x2f/0x40
[  216.936186]  [<ffffffff810bd9f1>] enable_mmiotrace+0x51/0x1e0
[  216.937850]  [<ffffffff811907ac>] mmio_trace_init+0x3c/0x70
[  216.939464]  [<ffffffff8118a59e>] tracing_set_tracer+0xfe/0x190
[  216.941167]  [<ffffffff8118a860>] tracing_set_trace_write+0x90/0xd0
[  216.942975]  [<ffffffff8123f73d>] ? do_filp_open+0x9d/0x100
[  216.944604]  [<ffffffff8122efb7>] __vfs_write+0x37/0x100
[  216.946136]  [<ffffffff81231ce8>] ? __sb_start_write+0x58/0x100
[  216.947847]  [<ffffffff813bd9bd>] ? security_file_permission+0x3d/0xc0
[  216.949727]  [<ffffffff8122f6b9>] vfs_write+0xa9/0x190
[  216.951211]  [<ffffffff81003176>] ? do_audit_syscall_entry+0x66/0x70
[  216.953041]  [<ffffffff812304b5>] SyS_write+0x55/0xc0
[  216.954509]  [<ffffffff81003e77>] ? syscall_return_slowpath+0xd7/0x1d0
[  216.956402]  [<ffffffff817a79ae>] entry_SYSCALL_64_fastpath+0x12/0x71
[  216.958256] Code: 81 ff 14 25 48 f0 b7 81 e9 c6 fe ff ff 48 8b 45 c8 65 48 33 04 25 28 00 00 00 75 11 48 83 c4 28 5b 41 5c 41 5d 41 5e 41 5f 5d c3 <0f> 0b e8 7a 48 01 00 66 2e 0f 1f 84 00 00 00 00
00 0f 1f 44 00
[  216.966294] RIP  [<ffffffff810b349f>] sync_global_pgds+0x18f/0x1a0
[  216.968106]  RSP <ffff880035cdfc58>
[  216.969198] ---[ end trace c824ada35f12984e ]---
[  216.970614] Kernel panic - not syncing: Fatal exception
[  216.973111] Kernel Offset: disabled
[  216.974138] ---[ end Kernel panic - not syncing: Fatal exception

Thanks,
-- 
Masami HIRAMATSU
Linux Technology Research Center, System Productivity Research Dept.
Center for Technology Innovation - Systems Engineering
Hitachi, Ltd., Research & Development Group
E-mail: masami.hiramatsu.pt@xxxxxxxxxxx
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