ref: 0f0270cdd612d6bc7f065b5c25c4cfffc2c0bd87 dir: /sys/src/libc/amd64/argv0.s/
GLOBL argv0(SB), $8 GLOBL _tos(SB), $8 GLOBL _privates(SB), $8 GLOBL _nprivates(SB), $4