This can be implemented entirely in userspace by calling tcgetattr().
To avoid screwing up the syscall indexes, this patch also adds a
mechanism for removing a syscall without shifting the index of other
syscalls.
Note that ports will still have to be rebuilt after this change,
as their LibC code will try to make the isatty() syscall on startup.
The Plan9 OS has this program that can test a system call with the
given arguments. For the most basic system calls it can be very
helpful and aid with testing or just to play with a given syscall
without writing a dedicated program.
Some examples:
syscall write 1 hello 5
syscall -o read 0 buf 5
syscall mkdir /tmp/my-dir
syscall exit 2
...