bash-4.4$ make ARCH=arm CROSS_COMPILE=arm-linux-gnu- -j3 uImage modules  CHK     include/linux/version.h
  CHK     include/generated/utsrelease.h
make[1]: 'include/generated/mach-types.h' is up to date.
  CALL    scripts/checksyscalls.sh
  CHK     include/generated/compile.h
  LD      init/mounts.o
  CC      arch/arm/kernel/return_address.o
init/do_mounts_rd.o: In function `return_address':
/home/matthew/Downloads/kernel/linux-sunxi/arch/arm/include/asm/ftrace.h:51: multiple definition of `return_address'
init/do_mounts.o:/home/matthew/Downloads/kernel/linux-sunxi/arch/arm/include/asm/ftrace.h:51: first defined here
init/do_mounts_initrd.o: In function `return_address':
/home/matthew/Downloads/kernel/linux-sunxi/arch/arm/include/asm/ftrace.h:51: multiple definition of `return_address'
init/do_mounts.o:/home/matthew/Downloads/kernel/linux-sunxi/arch/arm/include/asm/ftrace.h:51: first defined here
make[1]: *** [scripts/Makefile.build:429: init/mounts.o] Error 1
make: *** [Makefile:947: init] Error 2
make: *** Waiting for unfinished jobs....
  CC      arch/arm/kernel/sched_clock.o
  CC      arch/arm/kernel/setup.o
arch/arm/kernel/return_address.c:62:2: warning: #warning "TODO: return_address should use unwind tables" [-Wcpp]
 #warning "TODO: return_address should use unwind tables"
  ^~~~~~~
arch/arm/kernel/return_address.c:65:7: error: redefinition of ‘return_address’
 void *return_address(unsigned int level)
       ^~~~~~~~~~~~~~
In file included from include/linux/ftrace.h:19:0,
                 from arch/arm/kernel/return_address.c:12:
/home/matthew/Downloads/kernel/linux-sunxi/arch/arm/include/asm/ftrace.h:48:21: note: previous definition of ‘return_address’ was here
 extern inline void *return_address(unsigned int level)
                     ^~~~~~~~~~~~~~
make[1]: *** [scripts/Makefile.build:307: arch/arm/kernel/return_address.o] Error 1
make[1]: *** Waiting for unfinished jobs....
make: *** [Makefile:947: arch/arm/kernel] Error 2