ref: 6eb7e8e2b120c1511bdcf90e5b1d4e76383c7daf dir: /sys/src/libc/amd64/argv0.s/
GLOBL argv0(SB), $8 GLOBL _tos(SB), $8 GLOBL _privates(SB), $8 GLOBL _nprivates(SB), $4