ref: 4a30e556f7b66bcd2e68ab04bd3c9c42e1e4dfac dir: /sys/src/libc/amd64/argv0.s/
GLOBL argv0(SB), $8 GLOBL _tos(SB), $8 GLOBL _privates(SB), $8 GLOBL _nprivates(SB), $4