ref: 1e3790f7b5a7d5a01d63afe3956b36fa2d11ed0c dir: /sys/src/libc/amd64/argv0.s/
GLOBL argv0(SB), $8 GLOBL _tos(SB), $8 GLOBL _privates(SB), $8 GLOBL _nprivates(SB), $4