The enum_bitfields system never worked quite right, and always had edge cases where name
resolution for the SFINAE would fail. Move everything over to use util::bitset, which can
be constexpr and boils down to inline integer bitops in release mode.
Improved util::bitset itself, moving the array-backed base implementation into a new
util::sized_bitset, and making the single-inttype backed implementation the base case.
Also added a distinction between | or |= (which work with real bit values) and + or +=
(which work with bit indexes).
This is the first of two rather big changes to clean up includes
throughout the project. In this commit, the implicit semi-dependency on
libc that bonnibel adds to every module is removed. Previously, I was
sloppy with includes of libc headers and include directory order. Now,
the freestanding headers from libc are split out into libc_free, and an
implicit real dependency is added onto this module, unless `no_libc` is
set to `True`. The full libc needs to be explicitly specified as a
dependency to be used.
Several things needed to change in order to do this:
- Many places use `memset` or `memcpy` that cannot depend on libc. The
kernel has basic implementations of them itself for this reason. Now
those functions are moved into the lower-level `j6/memutils.h`, and
libc merely references them. Other modules are now free to reference
those functions from libj6 instead.
- The kernel's `assert.h` was renamed kassert.h (matching its `kassert`
function) so that the new `util/assert.h` can use `__has_include` to
detect it and make sure the `assert` macro is usable in libutil code.
- Several implementation header files under `__libj6/` also moved under
the new libc_free.
- A new `include_phase` property has been added to modules for Bonnibel,
which can be "normal" (default) or "late" which uses `-idirafter`
instead of `-I` for includes.
- Since `<utility>` and `<new>` are not freestanding, implementations of
`remove_reference`, `forward`, `move`, and `swap` were added to the
`util` namespace to replace those from `std`, and `util/new.h` was
added to declare `operator new` and `operator delete`.
The kernel log levels are now numerically reversed so that more-verbose
levels can be added to the end. Replaced 'debug' with 'verbose', and
added new 'spam' level.
When waking another thread, if that thread has a more urgent priority
than the current thread on the same CPU, send that CPU an IPI to tell it
to run its scheduler.
Related changes in this commit:
- Addition of the ipiSchedule isr (vector 0xe4) and its handler in
isr_handler().
- Change the APIC's send_ipi* functions to take an isr enum and not an
int for their vector parameter
- Thread TCBs now contain a pointer to their current CPU's cpu_data
structure
- Add the maybe_schedule() call to the scheduler, which sends the
schedule IPI to the given thread's CPU only when that CPU is running a
less-urgent thread.
- Move the locking of a run queue lock earlier in schedule() instead of
taking the lock in steal_work() and again in schedule().
First attempt at a UART driver. I'm not sure it's the most stable. Now
that userspace is handling displaying logs, also removed serial and log
output support from the kernel.
This is a rather large commit that is widely focused on cleaning things
out of the 'junk drawer' that is src/include. Most notably, several
things that were put in there because they needed somewhere where both
the kernel, boot, and init could read them have been moved to a new lib,
'bootproto'.
- Moved kernel_args.h and init_args.h to bootproto as kernel.h and
init.h, respectively.
- Moved counted.h and pointer_manipulation.h into util, renaming the
latter to util/pointers.h.
- Created a new src/include/arch for very arch-dependent definitions,
and moved some kernel_memory.h constants like frame size, page table
entry count, etc to arch/amd64/memory.h. Also created arch/memory.h
which detects platform and includes the former.
- Got rid of kernel_memory.h entirely in favor of a new, cog-based
approach. The new definitions/memory_layout.csv lists memory regions
in descending order from the top of memory, their sizes, and whether
they are shared outside the kernel (ie, boot needs to know them). The
new header bootproto/memory.h exposes the addresses of the shared
regions, while the kernel's memory.h gains the start and size of all
the regions. Also renamed the badly-named page-offset area the linear
area.
- The python build scripts got a few new features: the ability to parse
the csv mentioned above in a new memory.py module; the ability to add
dependencies to existing source files (The list of files that I had to
pull out of the main list just to add them with the dependency on
memory.h was getting too large. So I put them back into the sources
list, and added the dependency post-hoc.); and the ability to
reference 'source_root', 'build_root', and 'module_root' variables in
.module files.
- Some utility functions that were in the kernel's memory.h got moved to
util/pointers.h and util/misc.h, and misc.h's byteswap was renamed
byteswap32 to be more specific.
Continuing moving things out of kutil. The assert as implemented could
only ever work in the kernel, so remaining kutil uses of kassert have
been moved to including standard C assert instead.
Along the way, kassert was broken out into panic::panic and kassert,
and the panic.serial namespace was renamed panicking.
I'm a tabs guy. I like tabs, it's an elegant way to represent
indentation instead of brute-forcing it. But I have to admit that the
world seems to be going towards spaces, and tooling tends not to play
nice with tabs. So here we go, changing the whole repo to spaces since
I'm getting tired of all the inconsistent formatting.
The idle threads for the APs have intentionally tiny stacks. Logging is
currently an absolute hog of stack space, so avoid logging on the idle
stacks as much as possible.
Eventually we should instead just reclaim the physical pages used by
most of the stack instead of making them tiny.
Now that the other CPUs have been brought up, add support for scheduling
tasks on them. The scheduler now maintains separate ready/blocked lists
per CPU, and CPUs will attempt to balance load via periodic work
stealing.
Other changes as a result of this:
- The device manager no longer creates a local APIC object, but instead
just gathers relevant info from the APCI tables. Each CPU creates its
own local APIC object. This also spurred the APIC timer calibration to
become a static value, as all APICs are assumed to be symmetrical.
- Fixed a bug where the scheduler was popping the current task off of
its ready list, however the current task is never on the ready list
(except the idle task was first set up as both current and ready).
This was causing the lists to get into bad states. Now a task can only
ever be current or in a ready or blocked list.
- Got rid of the unused static process::s_processes list of all
processes, instead of trying to synchronize it via locks.
- Added spinlocks for synchronization to the scheduler and logger
objects.
KVM didn't like setting all the CR4 bits we wanted at once. I suspect
that means real hardware won't either. Delay the setting of the rest of
CR4 until after the CPU is in long mode - only set PAE and PGE from real
mode.
This very large commit is mainly focused on getting the APs started and
to a state where they're waiting to have work scheduled. (Actually
scheduling on them is for another commit.)
To do this, a bunch of major changes were needed:
- Moving a lot of the CPU initialization (including for the BSP) to
init_cpu(). This includes setting up IST stacks, writing MSRs, and
creating the cpu_data structure. For the APs, this also creates and
installs the GDT and TSS, and installs the global IDT.
- Creating the AP startup code, which tries to be as position
independent as possible. It's copied from its location to 0x8000 for
AP startup, and some of it is fixed at that address. The AP startup
code jumps from real mode to long mode with paging in one swell foop.
- Adding limited IPI capability to the lapic class. This will need to
improve.
- Renaming cpu/cpu.* to cpu/cpu_id.* because it was just annoying in GDB
and really isn't anything but cpu_id anymore.
- Moved all the GDT, TSS, and IDT code into their own files and made
them classes instead of a mess of free functions.
- Got rid of bsp_cpu_data everywhere. Now always call the new
current_cpu() to get the current CPU's cpu_data.
- Device manager keeps a list of APIC ids now. This should go somewhere
else eventually, device_manager needs to be refactored away.
- Moved some more things (notably the g_kernel_stacks vma) to the
pre-constructor setup in memory_bootstrap. That whole file is in bad
need of a refactor.
Now that the spinwait bug is fixed, the raised time for APIC calibration
can be put back to a lower value. It was previously raised thinking more
time would get a more accurate result -- but accuracy was not the issue.
Calling `spinwait()` was hanging due to improper computation of the
clock rate because justin did a dumb at math. Also the period can be
greater than 1ns, so the clock's units were updated to microseconds.
Create a clock class which can be queried for current timestamp in
nanoseconds. Also implements a simple HPET class as one possible clock
source.
Tags: time
Instead of many timer interrupts and decrementing a process' remaining
quanta, change to setting a single timer for when a process should be
preempted. If it uses its whole timeslice, demote it. If it uses less
than half before blocking, promote it. Determine timeslice based on
priority as well.
This change also required changing the apic timer interface to be purely
interval (in microseconds) based instead of its previous interval/tick
hybrid.
