ref: 1a782fda3e0fcc3205dc4b2a9b6ef3a75f68efb7 dir: /sys/src/libc/amd64/argv0.s/
GLOBL argv0(SB), $8 GLOBL _tos(SB), $8 GLOBL _privates(SB), $8 GLOBL _nprivates(SB), $4