1.fix bugs about timer interrupt
2.fix bug about huge map
3.fix bug about write

1. Increase user stack
2. When the thread exits, the memory is reclaimed in advance.

1. fix bugs about float number
2. fix bugs about user stack size
3. fix bugs about mmap
4. fix bugs about user's argument

net is so hard

update copy_to_user/copy_from_user impl

Dealing with tty echo issues.

add more syscall

make \r -> \n when stdin

add more syscall to support busybox

We need to ensure that the status update and reference count reduction
of the task exit are atomic.
When the task exits, the waiting task needs to be woken up according to
the value of clear_child_tid.

Now we use bitmap instead of buddy.
Buddy's implementation may contain bugs.

fix bugs about futex,signal and so on

ref maturin os

Boot from uboot using the fit image format.
Use cfg for conditional compilation.

add some syscall to support libc-test
fix some error

add some syscall support: writev/clock-gettime/ioctl/wxit_group.
cargo cmt

The link script in libc does not page-align each segment, so we need to
ensure that the data is loaded to the correct position when loading
data.