ref: 8fdf22d5fb5dca8b0acb1cbfccca1eda33b7d39f dir: /sys/src/libc/amd64/argv0.s/
GLOBL argv0(SB), $8 GLOBL _tos(SB), $8 GLOBL _privates(SB), $8 GLOBL _nprivates(SB), $4