ref: 23d6c796cd1dc0c9c2a2b910b79d2dc2bcdbb181 dir: /sys/src/libc/amd64/argv0.s/
GLOBL argv0(SB), $8 GLOBL _tos(SB), $8 GLOBL _privates(SB), $8 GLOBL _nprivates(SB), $4