Kprobe event string type argument in ftrace from ubuntu_kernel_selftests failed on B i386

This test in ftace:
    Kprobe event string type argument [FAIL]
failed with Bionic kernel on i386 (passed on other arches)

$ sudo ./ftracetest
=== Ftrace unit tests ===
[1] Basic trace file check [PASS]
[2] Basic test for tracers [PASS]
[3] Basic trace clock test [PASS]
[4] Basic event tracing check [PASS]
[5] event tracing - enable/disable with event level files [PASS]
[6] event tracing - restricts events based on pid [PASS]
[7] event tracing - enable/disable with subsystem level files [PASS]
[8] event tracing - enable/disable with top level files [PASS]
[9] ftrace - function graph filters with stack tracer [PASS]
[10] ftrace - function graph filters [PASS]
[11] ftrace - function glob filters [PASS]
[12] ftrace - function pid filters [PASS]
[13] ftrace - test for function event triggers [PASS]
[14] ftrace - function profiler with function tracing [PASS]
[15] ftrace - test reading of set_ftrace_filter [PASS]
[16] ftrace - test for function traceon/off triggers [PASS]
[17] Test creation and deletion of trace instances while setting an event [PASS]
[18] Test creation and deletion of trace instances [PASS]
[19] Kprobe dynamic event - adding and removing [PASS]
[20] Kprobe dynamic event - busy event check [PASS]
[21] Kprobe dynamic event with arguments [PASS]
[22] Kprobe event string type argument [FAIL]
[23] Kprobe event argument syntax [PASS]
[24] Kprobes event arguments with types [PASS]
[25] Kprobe event auto/manual naming [PASS]
[26] Kprobe dynamic event with function tracer [PASS]
[27] Kprobe dynamic event - probing module [PASS]
[28] Kretprobe dynamic event with arguments [PASS]
[29] Kretprobe dynamic event with maxactive [PASS]
[30] Register/unregister many kprobe events [PASS]
[31] Kprobe events - probe points [PASS]
[32] event trigger - test multiple actions on hist trigger [UNSUPPORTED]
[33] event trigger - test event enable/disable trigger [PASS]
[34] event trigger - test trigger filter [PASS]
[35] event trigger - test histogram modifiers [PASS]
[36] event trigger - test histogram trigger [PASS]
[37] event trigger - test multiple histogram triggers [PASS]
[38] event trigger - test snapshot-trigger [PASS]
[39] event trigger - test stacktrace-trigger [PASS]
[40] event trigger - test traceon/off trigger [PASS]
[41] (instance) Basic test for tracers [PASS]
[42] (instance) Basic trace clock test [PASS]
[43] (instance) event tracing - enable/disable with event level files [PASS]
[44] (instance) event tracing - restricts events based on pid [PASS]
[45] (instance) event tracing - enable/disable with subsystem level files [PASS]
[46] (instance) ftrace - test for function event triggers [PASS]
[47] (instance) ftrace - test for function traceon/off triggers [PASS]
[48] (instance) event trigger - test event enable/disable trigger [PASS]
[49] (instance) event trigger - test trigger filter [PASS]
[50] (instance) event trigger - test histogram modifiers [PASS]
[51] (instance) event trigger - test histogram trigger [PASS]
[52] (instance) event trigger - test multiple histogram triggers [PASS]

# of passed: 50
# of failed: 1
# of unresolved: 0
# of untested: 0
# of unsupported: 1
# of xfailed: 0
# of undefined(test bug): 0

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-4.15.0-43-generic 4.15.0-43.46
ProcVersionSignature: User Name 4.15.0-43.46-generic 4.15.18
Uname: Linux 4.15.0-43-generic i686
AlsaDevices:
 total 0
 crw-rw---- 1 root audio 116, 1 Jan 21 10:52 seq
 crw-rw---- 1 root audio 116, 33 Jan 21 10:52 timer
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay': 'aplay'
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: i386
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord': 'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
Date: Mon Jan 21 11:21:48 2019
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig': 'iwconfig'
MachineType: Dell Inc. PowerEdge R310
PciMultimedia:

ProcFB: 0 mgadrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-43-generic root=UUID=6aaa11f6-d386-4c0c-b4b8-38e6c408980a ro console=ttyS0,115200n8
RelatedPackageVersions:
 linux-restricted-modules-4.15.0-43-generic N/A
 linux-backports-modules-4.15.0-43-generic N/A
 linux-firmware 1.173.3
RfKill: Error: [Errno 2] No such file or directory: 'rfkill': 'rfkill'
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/18/2012
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.11.0
dmi.board.name: 05XKKK
dmi.board.vendor: Dell Inc.
dmi.board.version: A05
dmi.chassis.type: 23
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvr1.11.0:bd09/18/2012:svnDellInc.:pnPowerEdgeR310:pvr:rvnDellInc.:rn05XKKK:rvrA05:cvnDellInc.:ct23:cvr:
dmi.product.name: PowerEdge R310
dmi.sys.vendor: Dell Inc.