# # source codes # usermode.S # # # build command: arc-elf32-gcc -mcpu=arcem -nostdlib usermode.S -g -Wl,-Ttext=0x80000000 -Wl,--entry=_start -o usermode.elf # # qemu command: qemu-system-arc -cpu arcem -M simhs -kernel usermode.elf -s -S # # mdb command: mdb -nooptions -nogoifmain -toggle=include_local_symbols=1 -nsim -arcv2em -OKN usermode.elf .global _start .type _start, @function _start: lr r0, [status32] or r0, r0, 128 sr r0, [erstatus] mov r0, usermode sr r0, [eret] rtie .global usermode .type usermode, @function usermode: lr r0, [status32] clri r0 lr r0, [status32] brk