ref: eff7165c2ac8f4f1de511f87c6f68ecbdf0b3a1e dir: /sys/src/libc/amd64/argv0.s/
GLOBL argv0(SB), $8 GLOBL _tos(SB), $8 GLOBL _privates(SB), $8 GLOBL _nprivates(SB), $4