ref: ca2fa9596b5d0d893be28c6e8fd8a52a89a0c3c6 dir: /sys/src/libc/amd64/argv0.s/
GLOBL argv0(SB), $8 GLOBL _tos(SB), $8 GLOBL _privates(SB), $8 GLOBL _nprivates(SB), $4