The current strategy is simply to nuke all physical pages and force
reload them from disk. This is obviously not optimal and should eventually
be optimized. It should be fairly straightforward.
Userspace programs can now open /dev/gui_events and read a stream of GUI_Event
structs one at a time.
I was stuck on a stupid problem where we'd reenter Scheduler::yield() due to
having one of the has_data_available_for_reading() implementations using locks.
This is a lot better than having them in kmalloc memory. I'm gonna need
a way to keep track of which process owns which bitmap eventually,
maybe through some sort of resource keying system. We'll see.
This is really sweet! :^) The four instances of /bin/sh spawned at
startup now share their read-only text pages.
There are problems and limitations here, and plenty of room for
improvement. But it kinda works.
All right, we can now mmap() a file and it gets magically paged in from fs
in response to an NP page fault. This is really cool :^)
I need to refactor this to support sharing of read-only file-backed pages,
but it's cool to just have something working.
First of all, change sys$mmap to take a struct SC_mmap_params since our
sycsall calling convention can't handle more than 3 arguments.
This exposed a bug in Syscall::invoke() needing to use clobber lists.
It was a bit confusing to debug. :^)
Processes are either alive (with many substates), dead or forgiven.
A dead process is forgiven when the parent waitpid()s on it.
Dead orphans are also forgiven.
There's a lot of work to be done around this.
sys$fork() now clones all writable regions with per-page COW bits.
The pages are then mapped read-only and we handle a PF by COWing the pages.
This is quite delightful. Obviously there's lots of work to do still,
and it needs better data structures, but the general concept works.
We now make three VirtualConsoles at boot: tty0, tty1, and tty2.
We launch an instance of /bin/sh in each one.
You switch between them with Alt+1/2/3
How very very cool :^)
This took me a couple hours. :^)
The ELF loading code now allocates a single region for the entire
file and creates virtual memory mappings for the sections as needed.
Very nice!
I also added a generator cache to FileHandle. This way, multiple
reads to a generated file (i.e in a synthfs) can transparently
handle multiple calls to read() without the contents changing
between calls.
The cache is discarded at EOF (or when the FileHandle is destroyed.)
- Turn Keyboard into a CharacterDevice (85,1) at /dev/keyboard.
- Implement MM::unmapRegionsForTask() and MM::unmapRegion()
- Save SS correctly on interrupt.
- Add a simple Spawn syscall for launching another process.
- Move a bunch of IO syscall debug output behind DEBUG_IO.
- Have ASSERT do a "cli" immediately when failing.
This makes the output look proper every time.
- Implement a bunch of syscalls in LibC.
- Add a simple shell ("sh"). All it can do now is read a line
of text from /dev/keyboard and then try launching the specified
executable by calling spawn().
There are definitely bugs in here, but we're moving on forward.
This leaves interrupts enabled while we're in the kernel, which is
precisely what we want.
This uncovered a horrendous problem with kernel tasks silently
overflowing their stacks. For now I've simply increased the stack size
but I need a more MMU-y solution for this eventually.
