Since the CPU already does almost all necessary validation steps
for us, we don't really need to attempt to do this. Doing it
ourselves doesn't really work very reliably, because we'd have to
account for other processors modifying virtual memory, and we'd
have to account for e.g. pages not being able to be allocated
due to insufficient resources.
So change the copy_to/from_user (and associated helper functions)
to use the new safe_memcpy, which will return whether it succeeded
or not. The only manual validation step needed (which the CPU
can't perform for us) is making sure the pointers provided by user
mode aren't pointing to kernel mappings.
To make it easier to read/write from/to either kernel or user mode
data add the UserOrKernelBuffer helper class, which will internally
either use copy_from/to_user or directly memcpy, or pass the data
through directly using a temporary buffer on the stack.
Last but not least we need to keep syscall params trivial as we
need to copy them from/to user mode using copy_from/to_user.
This does not add any behaviour change to the processes, but it ties a
TTY to an active process group via TIOCSPGRP, and returns the TTY to the
kernel when all processes in the process group die.
Also makes the TTY keep a link to the original controlling process' parent (for
SIGCHLD) instead of the process itself.
This compiles, and fixes two bugs:
- setpgid() confusion (see previous commit)
- tcsetpgrp() now allows to set a non-empty process group even if
the group leader has already died. This makes Serenity slightly
more POSIX-compatible.
- Remove goofy _r suffix from syscall names.
- Don't take a signed buffer size.
- Use Userspace<T>.
- Make TTY::tty_name() return a String instead of a StringView.
As suggested by Joshua, this commit adds the 2-clause BSD license as a
comment block to the top of every source file.
For the first pass, I've just added myself for simplicity. I encourage
everyone to add themselves as copyright holders of any file they've
added or modified in some significant way. If I've added myself in
error somewhere, feel free to replace it with the appropriate copyright
holder instead.
Going forward, all new source files should include a license header.
The TTY driver now respects the ICANON flag, enabling basic line
editing like VKILL, VERASE, VEOF and VWERASE. Additionally,
ICANON is now set by default.
Basic echoing has can now be enabled via the ECHO flag, though
more complicated echoing like ECHOCTL or ECHONL has not been
implemented.
This papers over an immediate issue where pseudoterminals would choke
on more than 16 characters of pasted input in the GUI terminal.
Longer-term we should find a more elegant solution than using a static
size CircularQueue for this.
TTY::emit is called from an IRQ handler, and is used to push input data
into a buffer for later retrieval. Previously this was using DoubleBuffer,
but that class wants to take a lock. Our lock code wants to make sure
interrupts are enabled, but they're disabled while an IRQ handler is
running. This made the kernel sad, but this CircularQueue cheers it up by
avoiding the lock requirement completely.
After reading a bunch of POSIX specs, I've learned that a file descriptor
is the number that refers to a file description, not the description itself.
So this patch renames FileDescriptor to FileDescription, and Process now has
FileDescription* file_description(int fd).
Also run it across the whole tree to get everything using the One True Style.
We don't yet run this in an automated fashion as it's a little slow, but
there is a snippet to do so in makeall.sh.
