Here is a new, separate bug report about 'kASLR' and system booting
issues (v4.4.0-113.136 - v4.4.0-115-generic kernel versions):
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Linux 4.4.0-113.136 (i386/x86_32): failed to boot and BusyBox v1.22.1
built-in shell (initramfs).
Status in linux package in Ubuntu:
Status in linux source package in Xenial:
On Thu Feb 8, Linux kernel for Ubuntu 16.04.3 LTS has been updated to
the 4.4.0-113.136 version (xenial-proposed). However, after reboot,
plymouth freezes during start, and keys on an USB keyboard were in-
active. After several seconds, the BusyBox shell screen appeared. It
looks this way:
| BusyBox v1.22.1 (Ubuntu 1:1.22.0-15ubuntu1) built-in shell (ash)
| Enter 'help' for a list of built-in commands.
| (initramfs) _
Unfortunately, the USB keyboard does not work and does not respond.
The only way to solve this issue is a "hard reset" and in GRUB menu
choosing an earlier kernel, which is linux 4.4.0-112.135. Now,
everything works okay.
Proposed update to the Linux 4.4.0-113.136 contains many new updates
(please see 1.) It's an i386/x86_32 architecture, which does not
contain PTI yet, right? I'm asking, because mentioned -proposed
updates contains a couple of PTI-related patches and bugs in PTI can
cause a few different signatures of crashes etc. For example:
→ Crashes in early boot, especially around CPU bringup. Bugs in the
trampoline code or mappings cause these.
→ Userspace segfaults early in boot, sometimes manifesting as mount(8)
failing to mount the rootfs. These have tended to be TLB invalidation issues.
Usually invalidating the wrong PCID, or otherwise missing an invalidation.
NOTE: if it's about PCID, which is mentioned in a second point, there
is one patch in -proposed update: "x86/mm/32: Move
setup_clear_cpu_cap(X86_FEATURE_PCID) earlier". Maybe that's is the
cause of a boot failure? There are no errors in log files, such as
'/var/log/syslog' or '/var/log/kern.log'. However, it's a Celeron, "E"
series. So, I don't know if mentioned patches are good for this type
of processor etc.? Especially on i386/x86_32 architecture.
● UPDATE/WARNING: It seems, that 'kaslr' option is responsible for
this issue. After booting the latest v4.4.0-115.139 kernel, I've had
the same problems as described above. However, after removing 'kaslr'
option from a command line via GRUB menu, system started normally etc.
The latest, working kernel with 'kaslr' option is v4.4.0-112.135.
According to all of this I think, that 'kaslr' is not compatible with
some "Spectre & Meltdown" mitigation patches and fixes etc.
✗ Release ('/proc/version_signature'): Ubuntu 4.4.0-112.135-generic 4.4.98
✗ Architecture: i386/x86_32
✗ PCI ('lspci -vnvn'): 00:0a.0 PCI bridge : NVIDIA Corporation MCP73
PCI Express bridge [10de:056d] (rev a1) (prog-if 01 [Subtractive decode])
Capabilities: [b8] Subsystem: Gigabyte Technology Co., Ltd MCP73 PCI Express
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