ref: 71f807873b43a4d2a2e2c9d1acbe1d97b5fdf18c dir: /sys/src/libc/amd64/argv0.s/
GLOBL argv0(SB), $8 GLOBL _tos(SB), $8 GLOBL _privates(SB), $8 GLOBL _nprivates(SB), $4