ref: 6e2ab60ce7201e22eeb4a9f36f0cfd4d2391aedf dir: /sys/src/libc/amd64/argv0.s/
GLOBL argv0(SB), $8 GLOBL _tos(SB), $8 GLOBL _privates(SB), $8 GLOBL _nprivates(SB), $4