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.
Background: DoubleBuffer is a handy buffer class in the kernel that
allows you to keep writing to it from the "outside" while the "inside"
reads from it. It's used for things like LocalSocket and TTY's.
Internally, it has a read buffer and a write buffer, but the two will
swap places when the read buffer is exhausted (by reading from it.)
Before this patch, it was internally implemented as two Vector<u8>
that we would swap between when the reader side had exhausted the data
in the read buffer. Now instead we preallocate a large KBuffer (64KB*2)
on DoubleBuffer construction and use that throughout its lifetime.
This removes all the kmalloc heap traffic caused by DoubleBuffers :^)
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.
Okay, one "dunce hat" point for me. The new PTY majors conflicted with
PATAChannel. Now they are 200 for master and 201 for slave, not used
by anything else.. I hope!
The 1st master pseudoterminal had the same device ID as /dev/psaux
which was caught by an assertion in Device VFS registration.
This would cause us to overwrite the PS/2 mouse device registration
which was definitely not good.
This makes tcgetpgrp() on a master PTY return the PGID of the slave PTY
which is probably what you are looking for. I'm not sure how correct or
standardized this is, but it makes sense to me right now.
This reverts commit 1cca5142af.
This appears to be causing intermittent triple-faults and I don't know
why yet, so I'll just revert it to keep the tree in decent shape.
Background: DoubleBuffer is a handy buffer class in the kernel that
allows you to keep writing to it from the "outside" while the "inside"
reads from it. It's used for things like LocalSocket and PTY's.
Internally, it has a read buffer and a write buffer, but the two will
swap places when the read buffer is exhausted (by reading from it.)
Before this patch, it was internally implemented as two Vector<u8>
that we would swap between when the reader side had exhausted the data
in the read buffer. Now instead we preallocate a large KBuffer (64KB*2)
on DoubleBuffer construction and use that throughout its lifetime.
This removes all the kmalloc heap traffic caused by DoubleBuffers :^)
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).
