** Description changed:
== Justification ==
Running the ftrace in ubuntu_kernel_selftests repetitively against x86 Cosmic
kernel will cause system hang.
+ When this happens, you won't be able to ssh into this system, and no log
+ can be found in syslog.
+
This hang is caused by one of the sub-test: kprobe/multiple_kprobes
- Upstream discussion could be found here:
- https://lkml.org/lkml/2018/12/3/1219
+ Masami's comment from upstream discussion
(https://lkml.org/lkml/2018/12/3/1219):
+ In arch/x86/kernel/kprobes/opt.c, copy_optimized_instructions() does a copy
loop, but only update src and dest cursors, but not update real address which
is used for adjusting RIP relative instruction.
== Fix ==
43a1b0cb4 (kprobes/x86: Fix instruction patching corruption when copying more
than one RIP-relative instruction)
This patch is already in D.
- For B/C, they all have this ill-commit 63fef14 and this patch can be
cherry-picked. Note that for Bionic kernel it can only be triggered in this way
with kernel built with GCC-8.
+ For B/C, they all have this ill-commit 63fef14 and this patch can be
cherry-picked. Note that for Bionic kernel it can only be triggered in this way
with a kernel built with GCC-8.
For X, the ill-commit 63fef14 does not exist.
== Test ==
Test kernel for Cosmic and Bionic built with GCC-8:
http://people.canonical.com/~phlin/kernel/lp-1826385-ftrace-hang/
+ (To verify this for the Bionic, you will need to build a kernel with
+ GCC-8.)
+
Patch tested with a bare-metal and a KVM node, both of them can pass the
beating repetitively.
== Regression Potential ==
- Upstream fix limited to x86 architecture, and specific for kprobe.
+ Low, upstream fix specific for kprobe and limited to x86 architecture.
+
+ Although it's a bit difficult to trigger this on Bionic, I think it
+ worth this fix as it's quite straightforward.
+
== Original Bug Report ==
This issue is a bit strange.
The test has passed with Cosmic 4.18.0-18.19 generic kernel on AMD64
node during our SRU testing process.
https://pastebin.ubuntu.com/p/HN2vN6fCXn/
However, Tyler found that this test will hang after:
[30] Kretprobe dynamic event with maxactive [PASS]
[31] Register/unregister many kprobe events [PASS]
And this is 100% reproducible.
No relevant output in syslog.
This will need further investigation.
ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: linux-image-4.18.0-18-generic 4.18.0-18.19
ProcVersionSignature: User Name 4.18.0-18.19-generic 4.18.20
Uname: Linux 4.18.0-18-generic x86_64
AlsaDevices:
total 0
crw-rw---- 1 root audio 116, 1 Apr 25 07:16 seq
crw-rw---- 1 root audio 116, 33 Apr 25 07:16 timer
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay': 'aplay'
ApportVersion: 2.20.10-0ubuntu13.2
Architecture: amd64
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: Thu Apr 25 07:18:51 2019
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig': 'iwconfig'
Lsusb: Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
MachineType: QEMU Standard PC (i440FX + PIIX, 1996)
PciMultimedia:
ProcFB: 0 cirrusdrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.18.0-18-generic
root=UUID=2f68c627-8ab4-40d5-8c06-6563436d0f96 ro
RelatedPackageVersions:
linux-restricted-modules-4.18.0-18-generic N/A
linux-backports-modules-4.18.0-18-generic N/A
linux-firmware 1.175.3
RfKill: Error: [Errno 2] No such file or directory: 'rfkill': 'rfkill'
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 04/01/2014
dmi.bios.vendor: SeaBIOS
dmi.bios.version: Ubuntu-1.8.2-1ubuntu1
dmi.chassis.type: 1
dmi.chassis.vendor: QEMU
dmi.chassis.version: pc-i440fx-xenial
dmi.modalias:
dmi:bvnSeaBIOS:bvrUbuntu-1.8.2-1ubuntu1:bd04/01/2014:svnQEMU:pnStandardPC(i440FX+PIIX,1996):pvrpc-i440fx-xenial:cvnQEMU:ct1:cvrpc-i440fx-xenial:
dmi.product.name: Standard PC (i440FX + PIIX, 1996)
dmi.product.version: pc-i440fx-xenial
dmi.sys.vendor: QEMU
** Also affects: linux (Ubuntu Bionic)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1826385
Title:
ftrace in ubuntu_kernel_selftests hang with Cosmic kernel
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