ref: 4a6ab355c1af789f7ddb4edbf4d82d17efd9d2bf dir: /sys/src/libc/amd64/argv0.s/
GLOBL argv0(SB), $8 GLOBL _tos(SB), $8 GLOBL _privates(SB), $8 GLOBL _nprivates(SB), $4