The new one is write(fd, buf, count).
The old one was write(buf, count).
So the old one tries to pass buf as a file descriptor, and write() complains that 4000000 is too large of a file descriptor and throws EBADF.
We now use the new syscall, through the wrapper that fwrite() provides us.
Kernel: Add an errno.h header with definitions for each header,
and return those, negated, from syscalls when there is an error.
mmap() returns an invalid address with errno encoded, instead of
returning a negated errno; this address is encoded as ffffffffffffffEE
where EE is errno in hex.
libc: make syscall() return -1 and set errno on error, instead of
returning the raw return value of the system call. Also, add mmap()
and munmap() wrappers in sys/mman.h :).
userspace: make the memeater program show the value of errno
when allocating memory fails.
Things to improve: add perror() and strerror() to make the errno
experience even better! >.<
