[Xperia Z3 Compact Original Android Development] seXneo:
I got one of those random reboots during charging and wanted to get /proc/last_kmsg

But it doesn't exist at all. /proc/kmsg is there, I can read it as root

Is /proc/last_kmsg missing for you as well?

These are the contents of my /proc folder

{many folders with numbers}
dr-xr-xr-x 3 root root 0 2016-12-11 15:03 asound
dr-xr-xr-x 3 root root 0 2016-12-11 15:03 bluetooth
-r--r--r-- 1 root root 0 2016-12-11 15:03 buddyinfo
dr-xr-xr-x 3 root root 0 2016-12-11 15:03 bus
-r--r--r-- 1 root root 0 2016-12-11 15:03 cgroups
-r--r----- 1 root radio 0 2016-12-11 15:03 cmdline
-r--r--r-- 1 root root 0 2016-12-11 15:03 consoles
dr-xr-xr-x 2 root root 0 2016-12-11 15:03 cpu
-r--r--r-- 1 root root 0 2016-12-11 15:03 cpuinfo
-r--r--r-- 1 root root 0 2016-12-11 15:03 crypto
dr-xr-xr-x 8 root root 0 2016-12-11 15:03 device-tree
-r--r--r-- 1 root root 0 2016-12-11 15:03 devices
-r--r--r-- 1 root root 0 2016-12-11 15:03 diskstats
dr-xr-xr-x 2 root root 0 2016-12-11 15:03 driver
-r--r--r-- 1 root root 0 2016-12-11 15:03 execdomains
-r--r--r-- 1 root root 0 2016-12-11 15:03 fb
-r--r--r-- 1 root root 0 2016-12-11 15:03 filesystems
dr-xr-xr-x 5 root root 0 2016-12-11 15:03 fs
-r--r--r-- 1 root root 0 2016-12-11 15:03 interrupts
-r-------- 1 root root 0 2016-12-11 15:03 iomem
-r--r--r-- 1 root root 0 2016-12-11 15:03 ioports
dr-xr-xr-x 327 root root 0 2016-12-11 15:03 irq
-r--r--r-- 1 root root 0 2016-12-11 15:03 kallsyms
-r--r--r-- 1 root root 0 2016-12-11 15:03 key-users
-r--r----- 1 root system 0 1970-09-25 22:22 kmsg
-r-------- 1 root root 0 2016-12-11 15:03 kpagecount
-r-------- 1 root root 0 2016-12-11 15:03 kpageflags
-r--r--r-- 1 root root 0 2016-12-11 15:03 loadavg
-r--r--r-- 1 root root 0 2016-12-11 15:03 locks
-r--r--r-- 1 root root 0 2016-12-11 15:03 meminfo
-r--r--r-- 1 root root 0 2016-12-11 15:03 misc
-r--r--r-- 1 root root 0 2016-12-11 15:03 modem_exception
lrwxrwxrwx 1 root root 11 2016-12-11 15:03 mounts -> self/mounts
lrwxrwxrwx 1 root root 8 2016-12-11 15:03 net -> self/net
-r--r--r-- 1 root root 0 2016-12-11 15:03 pagetypeinfo
-r--r--r-- 1 root root 0 2016-12-11 15:03 partitions
-r--r--r-- 1 root root 0 2016-12-11 15:03 sched_debug
-r--r--r-- 1 root root 0 2016-12-11 15:03 schedstat
dr-xr-xr-x 3 root root 0 2016-12-11 15:03 scsi
lrwxrwxrwx 1 root root 0 1970-01-01 01:00 self -> 6700
-r--r--r-- 1 root root 0 2016-12-11 15:03 softirqs
-r--r--r-- 1 root root 0 2016-12-11 15:03 stat
-r--r--r-- 1 root root 0 2016-12-11 15:03 swaps
dr-xr-xr-x 1 root root 0 2016-12-11 15:03 sys
--w--w---- 1 root system 0 2016-12-11 15:03 sysrq-trigger
-r--r--r-- 1 root root 0 2016-12-11 15:03 timer_list
-rw-r--r-- 1 root root 0 2016-12-11 15:03 timer_stats
dr-xr-xr-x 4 root root 0 2016-12-11 15:03 tty
dr-xr-xr-x 2 root root 0 2016-12-11 15:03 uid_cputime
dr-xr-xr-x 18 root root 0 2016-12-11 15:03 uid_stat
-r--r--r-- 1 root root 0 2016-12-11 15:03 uptime
-r--r--r-- 1 root root 0 2016-12-11 15:03 version
-r--r----- 1 root log 0 2016-12-11 15:03 vmallocinfo
-r--r--r-- 1 root root 0 2016-12-11 15:03 vmstat
-r--r--r-- 1 root root 0 2016-12-11 15:03 zoneinfo

I have a quick charge 2.0 charger. Over night I charged with Sony stock charger and got no reboots.