Initial step of paging now just prepares fast page for heap, actual page
table initialization happens after heap is initialized which allows
x86_64 to never depend on kmalloc for pages.
Processor's stacks are now also spawned with PMM/VMM allocated stacks
instead of kmalloc identity mapped.
There is no need for them to be uncached. Having them as uncached killed
the networking performance, over 90% time was spent in kernel out of
which 80% was in checksum calculation and memcpy, half each (measured in
qemu with e1000e)
I don't know why I though the block chain had to be stored fully in the
ThreadBlocker, that did not even fix the problem I was trying to fix
when I last rewrote it. Roll back to doubly linked list of block chain
and now just check that the node is contained within the ThreadBlocker
before removing and after acquiring the ThreadBlocker's lock. Also there
is no need to have a separate lock the node's blocker field. We can just
perform an atomic reads and writes to it. We can still get a blocker
that the node is no longer part of, but this can be resolved with a
simple check. This patch reduces ThreadBlocker's size from over 200
bytes to just 12 bytes +4 bytes padding
Also add custom load addresses for x86_64 target. This allows qemu to
load the kernel with -kernel argument. Without these addresses qemu
would refuse to load as it only supports 32 bit ELFs, but as our kernel
starts in 32 bit mode anyway, we can just load it!
This was just RefPtr<OpenFileDescription> and descriptor flags.
Descriptor flags only define O_CLOEXEC, so we can just store fd's
cloexec status in a bitmap rather than separate fields. This cuts down
the size of OpenFileDescriptorSet to basically half!
Kernel syscall API no longer zeros all unused argument registers and
libc now uses inlined syscall macro internally. This significantly
cleans up generated code for basic syscall wrapper functions.
Instead of keeping track of the current time and rescheduling when
interval has passed, keep track of the next expected reschedule time.
This prevents theoretically missing every second pre-emption when
scheduler's timer is interrupting at same rate as the interval.
Initially allocate all physical memory except kernel memory and boot
modules. Before we just skipped all memory before kernel boot modules.
Also release memory used by boot modules after the kernel is up and
running. Once the boot modules are loaded, there is no need to keep them
in memory.
We now appreciate sa_mask and SA_NODEFER and change the signal mask for
the duration of signal handler. This is done by making a sigprocmask
syscall at the end of the signal handler. Back-to-back signals will
still grow stack as original registers are popped AFTER the block mask
is updated. I guess this is why linux has sigreturn(?).
Current cpu index is stored at either segment. If userspace sets that
segment, kernel will not overwrite it on every reschedule. This is fine
as long as user program does not use anything that relies on it :)
We need to have interrupts enabled when signal kills the process as
process does mutex locking. Also signals are now only checked when
returning to userspace in the same place where userspace segments are
loaded.
