kernel: keep legacy throne tracker as an option

kernel: keep legacy throne tracker as an option

This change restores older throne tracker that uses packages.list scanning
to track app UIDs. It's intended for ultra-legacy Linux 3.X kernels that
experience deadlocks or crashes with the newer implementation due to issues
in user_data_actor().

We have to remember that the whole iterate_dir, and filldir subsystem is way
different on 3.X.

Changes:
- CONFIG_KSU_THRONE_TRACKER_LEGACY in Kconfig
- conditional compilation in Makefile
- throne_tracker_legacy.c which keeps the old implementation

Enable this option if newer throne tracker (tiann #2757crashes on you.)

Co-authored-by: backslashxx <118538522+backslashxx@users.noreply.github.com>

kernel/Makefile

@@ -3,7 +3,6 @@ kernelsu-objs += allowlist.o
 kernelsu-objs += dynamic_manager.o
 kernelsu-objs += apk_sign.o
 kernelsu-objs += sucompat.o
-kernelsu-objs += throne_tracker.o
 kernelsu-objs += core_hook.o
 kernelsu-objs += ksud.o
 kernelsu-objs += embed_ksud.o
@@ -17,6 +16,12 @@ kernelsu-objs += selinux/selinux.o
 kernelsu-objs += selinux/sepolicy.o
 kernelsu-objs += selinux/rules.o
 
+ifeq ($(CONFIG_KSU_THRONE_TRACKER_LEGACY),y)
+	kernelsu-objs += throne_tracker_legacy.o
+else
+	kernelsu-objs += throne_tracker.o
+endif
+
 ccflags-y += -I$(srctree)/security/selinux -I$(srctree)/security/selinux/include
 ccflags-y += -I$(objtree)/security/selinux -include $(srctree)/include/uapi/asm-generic/errno.h