ref: 1a67cd2c4400bc5e0a6f79b2be0b1fc1b324ad64 dir: /sys/src/libc/amd64/argv0.s/
GLOBL argv0(SB), $8 GLOBL _tos(SB), $8 GLOBL _privates(SB), $8 GLOBL _nprivates(SB), $4