ref: 03e6d3a0f06b1f1dc2b70bf7d236e8c96bbfa120 dir: /sys/src/libc/amd64/argv0.s/
GLOBL argv0(SB), $8 GLOBL _tos(SB), $8 GLOBL _privates(SB), $8 GLOBL _nprivates(SB), $4