ref: 5f7a6b7ea3c4ae1b51beffe3309e9b6b0491e71f dir: /sys/src/libc/amd64/argv0.s/
GLOBL argv0(SB), $8 GLOBL _tos(SB), $8 GLOBL _privates(SB), $8 GLOBL _nprivates(SB), $4