Re: [PATCH v2 2/2] tracing/kprobe: Add kprobe_event= boot parameter

Anders Roxell
2019-05-28T12:23:57Z

On Wed, 22 May 2019 at 10:32, Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> Add kprobe_event= boot parameter to define kprobe events
> at boot time.
> The definition syntax is similar to tracefs/kprobe_events
> interface, but use ',' and ';' instead of ' ' and '\n'
> respectively. e.g.
>
> kprobe_event=p,vfs_read,$arg1,$arg2
>
> This puts a probe on vfs_read with argument1 and 2, and
> enable the new event.
>
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>

I built an arm64 kernel from todays linux-next tag next-20190528 and
ran in to this issue when I booted it up in qemu:

[ 9.068772][ T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted
5.2.0-rc2-next-20190528-00019-g9a6008710716 #8
[ 9.072893][ T1] Hardware name: linux,dummy-virt (DT)
[ 9.075143][ T1] pstate: 80400005 (Nzcv daif +PAN -UAO)
[ 9.077528][ T1] pc : kprobe_target+0x0/0x30
[ 9.079479][ T1] lr : init_test_probes+0x134/0x540
[ 9.081611][ T1] sp : ffff80003f51fbe0
[ 9.083331][ T1] x29: ffff80003f51fbe0 x28: ffff200013c17820
[ 9.085906][ T1] x27: ffff200015d3ab40 x26: ffff2000122bb120
[ 9.088491][ T1] x25: 0000000000000000 x24: ffff200013c08ae0
[ 9.091068][ T1] x23: ffff200015d39000 x22: ffff200013a15ac8
[ 9.093667][ T1] x21: 1ffff00007ea3f86 x20: ffff200015d39420
[ 9.096214][ T1] x19: ffff2000122bad20 x18: 0000000000001400
[ 9.098831][ T1] x17: 0000000000000000 x16: ffff80003f510040
[ 9.101410][ T1] x15: 0000000000001480 x14: 1ffff00007ea3ea2
[ 9.103963][ T1] x13: 00000000f1f1f1f1 x12: ffff040002782e0d
[ 9.106549][ T1] x11: 1fffe40002782e0c x10: ffff040002782e0c
[ 9.109120][ T1] x9 : 1fffe40002782e0c x8 : dfff200000000000
[ 9.111676][ T1] x7 : ffff040002782e0d x6 : ffff200013c17067
[ 9.114234][ T1] x5 : ffff80003f510040 x4 : 0000000000000000
[ 9.116843][ T1] x3 : ffff200010427508 x2 : 0000000000000000
[ 9.119409][ T1] x1 : ffff200010426e10 x0 : 0000000000a6326b
[ 9.121980][ T1] Call trace:
[ 9.123380][ T1] kprobe_target+0x0/0x30
[ 9.125205][ T1] init_kprobes+0x2b8/0x300
[ 9.127074][ T1] do_one_initcall+0x4c0/0xa68
[ 9.129076][ T1] kernel_init_freeable+0x3c4/0x4e4
[ 9.131234][ T1] kernel_init+0x14/0x1fc
[ 9.133032][ T1] ret_from_fork+0x10/0x18
[ 9.134908][ T1] Code: a9446bf9 f9402bfb a8d87bfd d65f03c0 (d4200080)
[ 9.137845][ T1] ---[ end trace 49243ee03446b072 ]---
[ 9.140114][ T1] Kernel panic - not syncing: Fatal exception
[ 9.142684][ T1] ---[ end Kernel panic - not syncing: Fatal exception ]---

I bisected down to this commit as the one that introduces this issue.
I'm unsure why this causes the call trace though, any ideas?

Cheers,
Anders