ref: 1c30bd451e1813f1cf9f9db4d7c1a4f3f95d1e37 dir: /sys/src/libc/amd64/argv0.s/
GLOBL argv0(SB), $8 GLOBL _tos(SB), $8 GLOBL _privates(SB), $8 GLOBL _nprivates(SB), $4