options/posix: sys_dup should not accept a flags parameter

[64]

Instead, there should be a sys_dup3 syscall as per Linux.

Alternatively we could keep it how it is and inside the Linux sysdeps use a fnctl(F_DUPFD_CLOEXEC) call to handle it.

[avdgrinten]

Hm? What prevents you from implementing sys_dup based on syscall(SYS_dup3) on Linux?

[64]

What should the value of newfd be?

[avdgrinten]

That's indeed an issue. I guess we should simply use fcntl(F_DUPFD_CLOEXEC) instead.

[ArsenArsen]

That alters flags to add CLOEXEC. Matt discovered that the only use of the flags argument in sys_dup is in the managarm sysdep (the rest calls dup with zero), so we could just add an overload in that sysdep instead of adding the argument to the sysdep API

[avdgrinten]

Well, there is only a single flag that can be set (O_CLOEXEC), so one can always either use F_DUPFD/dup (which unsets the flag) or F_DUPFD_CLOEXEC.

[ArsenArsen]

The limit of which flags happen here could change in the future, though. It's more forward compatible to just refactor the Managarm sysdep

[64]

I would also prefer to get rid of that parameter, but changing the other sysdeps might be a bit messy.

[ArsenArsen]

why? AFAIK, this kind of change is why they're in tree