ref: 3fa5aaa1bcb9f1ba80e708aea3672fbf4b7f098d dir: /sys/src/libc/amd64/argv0.s/
GLOBL argv0(SB), $8 GLOBL _tos(SB), $8 GLOBL _privates(SB), $8 GLOBL _nprivates(SB), $4