[Fire Android Development] hadlock:
FYI one of the major changes with 5.1.2 was that Amazon removed whole device encryption. Given Apple's troubles with the FBI lately this may or may not have something to do with that but let's not start a flame war here :angel: :cyclops:

edit: looks like this is where it all falls apart. I dug in to the BAT file and ran the commands in sequence to see if there was a small issue I would work around. My guess here is that they've disabled the androidboot.unlocked_kernel command:

>files\fastboot.exe oem append-cmdline "androidboot.unlocked_kernel=true"
...
FAILED (remote: unknown command)
finished. total time: 0.000s

Here was my output running your tool on my 5.1.2 device today, if that helps at all. Device does reboot in to fastboot mode, fails, then boots in to `normal` mode where it throws a bunch of file permission errors. It would appear that the device is unrootable until some genius figures out how to root a 5.1.2 device. Without further adieu:

--------------------------------------------------------------------------------
[*] NOTE this will not work unless your fastboot drivers are installed
[*] see option 1 ADB Driver install.
[*] Once the screen is black and says fastboot in the corner
[*] press and key to continue the script.
--------------------------------------------------------------------------------
...
FAILED (remote: unknown command)
finished. total time: 0.006s
resuming boot...
OKAY [ 0.016s]
finished. total time: 0.016s
--------------------------------------------------------------------------------
[*] your device is rebooting and will inject root files.
--------------------------------------------------------------------------------
remount of system failed: Permission denied
remount failed
1713 KB/s (170232 bytes in 0.097s)
1 KB/s (1976 bytes in 1.000s)
2886 KB/s (75364 bytes in 0.025s)
4422 KB/s (5904943 bytes in 1.303s)
8353 KB/s (29972 bytes in 0.003s)
mkdir failed for /system/app/SuperSU, Read-only file system
Unable to open /system/app/SuperSU: No such file or directory
chcon: Could not label /system/app/SuperSU with u:object_r:system_file:s0: No such file or directory
cp: /system/app/SuperSU/SuperSU.apk: No such file or directory
Unable to open /system/app/SuperSU/SuperSU.apk: No such file or directory
chcon: Could not label /system/app/SuperSU/SuperSU.apk with u:object_r:system_file:s0: No such file or directory
mkdir failed for /system/bin/.ext, Read-only file system
Unable to open /system/bin/.ext: No such file or directory
chcon: Could not label /system/bin/.ext with u:object_r:system_file:s0: No such file or directory
cp: /system/xbin/su: Read-only file system
Unable to open /system/xbin/su: No such file or directory
chcon: Could not label /system/xbin/su with u:object_r:system_file:s0: No such file or directory
cp: /system/bin/.ext/.su: No such file or directory
Unable to open /system/bin/.ext/.su: No such file or directory
chcon: Could not label /system/bin/.ext/.su with u:object_r:system_file:s0: No such file or directory
cp: /system/xbin/daemonsu: Read-only file system
Unable to open /system/xbin/daemonsu: No such file or directory
chcon: Could not label /system/xbin/daemonsu with u:object_r:system_file:s0: No such file or directory
cp: /system/xbin/sugote: Read-only file system
Unable to open /system/xbin/sugote: No such file or directory
chcon: Could not label /system/xbin/sugote with u:object_r:zygote_exec:s0: No such file or directory
cp: /system/xbin/supolicy: Read-only file system
Unable to open /system/xbin/supolicy: No such file or directory
chcon: Could not label /system/xbin/supolicy with u:object_r:system_file:s0: No such file or directory
cp: /system/lib/libsupol.so: Read-only file system
Unable to open /system/lib/libsupol.so: No such file or directory
chcon: Could not label /system/lib/libsupol.so with u:object_r:system_file:s0: No such file or directory
cp: /system/xbin/sugote-mksh: Read-only file system
Unable to open /system/xbin/sugote-mksh: No such file or directory
chcon: Could not label /system/xbin/sugote-mksh with u:object_r:system_file:s0: No such file or directory
cp: /system/bin/app_process32_original: Read-only file system
Unable to open /system/bin/app_process32_original: No such file or directory
chcon: Could not label /system/bin/app_process32_original with u:object_r:zygote_exec:s0: No such file or directory
cp: /system/bin/app_process_init: Read-only file system
Unable to open /system/bin/app_process_init: No such file or directory
chcon: Could not label /system/bin/app_process_init with u:object_r:system_file:s0: No such file or directory
rm: /system/bin/app_process: Read-only file system
override rwxr-xr-x root:shell for '/system/bin/app_process32'?

---------- Post added at 11:19 AM ---------- Previous post was at 10:24 AM ----------

Ok, on page 2 of /cache/recovery/lastkmsg it still says:

nt_pool=3240k androidboot.unlocked_kernel=false androidboot.rpmb_state=1 androidboot.secure_cpu=1 android [ 0.000000]-(0)[0:swapper]

So.... did they just disable true for that first flag? Do those other two flags look familiar to you, or maybe I just need to flip it to state=0 and/or secur_cpu=0 ?