Previously processes and threads would be deleted by the scheduler. Now,
only delete them based on refcounts - this allows joining an
already-exited thread, for instance.
For the coming switch to cap/handle ref-counting being the main lifetime
determiner of objects, get rid of self handles for threads and processes
to avoid circular references. Instead, passing 0 to syscalls expecting a
thread or process handle signifies "this process/thread".
Add a version of thread::block() that takes a lock and releases it after
marking the thread as unready, but before calling the scheduler.
Use this version of block() in the wait_queue.
Split out different constants for scheduler::idle_priority and
scheduler::max_priority, so that threads never fall to the same priority
level as the idle threads.
This commit changes the add_user_thunk to point to a new routine,
initialize_user_cpu, which sets all the registers that were previously
unset when starting a new user thread. The values for rdi and rsi are
popped off the initial stack values that add_user_thunk sets up, so that
user thread procs can take up to two arguments.
To suppor this, j6_thread_create gained two new arguments, which are
passed on to the thread.
This also let me finally get rid of the hack of passing an argument in
rsp when starting init.
The status code from thread exit had too many issues, (eg, how does it
relate to process exit code? what happens when different threads exit
with different exit codes?) and not enough value, so I'm getting rid of
it.
Instead of handles / capabilities having numeric ids that are only valid
for the owning process, they are now global in a system capabilities
table. This will allow for specifying capabilities in IPC that doesn't
need to be kernel-controlled.
Processes will still need to be granted access to given capabilities,
but that can become a simpler system call than the current method of
sending them through mailbox messages (and worse, having to translate
every one into a new capability like was the case before). In order to
track which handles a process has access to, a new node_set based on
node_map allows for an efficient storage and lookup of handles.
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().
In preparation for the new mailbox IPC model, blocking threads needed an
overhaul. The `wait_on_*` and `wake_on_*` methods are gone, and the
`block()` and `wake()` calls on threads now pass a value between the
waker and the blocked thread.
As part of this change, the concept of signals on the base kobject class
was removed, along with the queue of blocked threads waiting on any
given object. Signals are now exclusively the domain of the event object
type, and the new wait_queue utility class helps manage waiting threads
when an object does actually need this functionality. In some cases (eg,
logger) an event object is used instead of the lower-level wait_queue.
Since this change has a lot of ramifications, this large commit includes
the following additional changes:
- The j6_object_wait, j6_object_wait_many, and j6_thread_pause syscalls
have been removed.
- The j6_event_clear syscall has been removed - events are "cleared" by
reading them now. A new j6_event_wait syscall has been added to read
events.
- The generic close() method on kobject has been removed.
- The on_no_handles() method on kobject now deletes the object by
default, and needs to be overridden by classes that should not be.
- The j6_system_bind_irq syscall now takes an event handle, as well as a
signal that the IRQ should set on the event. IRQs will cause a waiting
thread to be woken with the appropriate bit set.
- Threads waking due to timeout is simplified to just having a
wake_timeout() accessor that returns a timestamp.
- The new wait_queue uses util::deque, which caused the disovery of two
bugs in the deque implementation: empty deques could still have a
single array allocated and thus return true for empty(), and new
arrays getting allocated were not being zeroed first.
- Exposed a new erase() method on util::map that takes a node pointer
instead of a key, skipping lookup.
If the thread waiting is the current thread, it should have the result
when it wakes. Might as well return it, so that syscalls that know
they're putting the current thread to sleep can get the result easily.
A spinlock was recenly added to thread wait states, so that they
couldn't get stuck if their wake event happened while setting the wake
state, and cause the thread to deadlock. But the scoped_lock objects
locking that spinlock were being instantiated as temporaries and
immediately being thrown away because I forgot to name them.
This commit contains a couple large, interdependent changes:
- In preparation for capability checking, the _syscall_verify_*
functions now load most handles passed in, and verify that they exist
and are of the correct type. Lists and out-handles are not converted
to objects.
- Also in preparation for capability checking, the internal
representation of handles has changed. j6_handle_t is now 32 bits, and
a new j6_cap_t (also 32 bits) is added. Handles of a process are now a
util::map<j6_handle_t, handle> where handle is a new struct containing
the id, capabilities, and object pointer.
- The kernel object definition DSL gained a few changes to support auto
generating the handle -> object conversion in the _syscall_verify_*
functions, mostly knowing the object type, and an optional "cname"
attribute on objects where their names differ from C++ code.
(Specifically vma/vm_area)
- Kernel object code and other code under kernel/objects is now in a new
obj:: namespace, because fuck you <cstdlib> for putting "system" in
the global namespace. Why even have that header then?
- Kernel object types constructed with the construct_handle helper now
have a creation_caps static member to declare what capabilities a
newly created object's handle should have.
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.
The j6threads command shows the current thread, ready threads, and
blocked threads for a given CPU.
To support this, TCB structs gained a pointer to their thread (instead
of trying to do offset magic) and threads gained a pointer to their
creator. Also removed thread::from_tcb() now that the TCB has a pointer.
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.
Now that kutil has no kernel-specific code in it anymore, it can
actually be linked to by anything, so I'm renaming it 'util'.
Also, I've tried to unify the way that the system libraries from
src/libraries are #included using <> instead of "".
Other small change: util::bip_buffer got a spinlock to guard against
state corruption.
The moving of kernel-only code out of kutil continues. (See 042f061)
This commit moves the following:
- The heap allocator code
- memory.cpp/h which means:
- letting string.h be the right header for memset and memcpy, still
including an implementation of it for the kernel though, since
we're not linking libc to the kernel
- Changing calls to kalloc/kfree to new/delete in kutil containers
that aren't going to be merged into the kernel
- Fixing a problem with stdalign.h from libc, which was causing issues
for type_traits.
Stop creating stacks in user space for user threads, that should be done
by the thread's creator. This change adds process and stack_top
arguments to the thread_create syscall, so that threads can be created
in other processes, and given a stack address.
Also included is a fix in add_thunk_user due to the r11/flags change.
THIS COMMIT BREAKS USERSPACE. See subsequent commits for the user side
changes related to this change.
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.
Add the object_wait_many syscall to allow programs to wait for signals
on multiple objects at once. Also removed the object argument to
thread::wait_on_signals, which does nothing with it. That information is
saved in the thread being in the object's blocked threads list.
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.
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.
The previous method of VMA page tracking relied on the VMA always being
mapped at least into one space and just kept track of pages in the
spaces' page tables. This had a number of drawbacks, and the mapper
system was too complex without much benefit.
Now make VMAs themselves keep track of spaces that they're a part of,
and make them responsible for knowing what page goes where. This
simplifies most types of VMA greatly. The new vm_area_open (nee
vm_area_shared, but there is now no reason for most VMAs to be
explicitly shareable) adds a 64-ary radix tree for tracking allocated
pages.
The page_tree cannot yet handle taking pages away, but this isn't
something jsix can do yet anyway.
In preparation for moving things to the init process, move process
loading out of the scheduler. memory_bootstrap now has a
load_simple_process function for mapping an args::program into memory,
and the stack setup has been simplified (though all the initv values are
still being added by the kernel - this needs rework) and normalized to
use the thread::add_thunk_user code path.
It was not consistent how processes got handles to themselves or their
threads, ending up with double entries. Now make such handles automatic
and expose them with new self_handle() methods.
Instead of making every callsite that may make a thread do a blocking
operation also invoke the scheduler, move that logic into thread
implementation - if the thread is blocking and is the current thread,
call schedule().
Related changes in this commit:
- Also make exiting threads and processes call the scheduler when
blocking.
- Threads start blocked, and get automatically added to the scheduler's
blocked list.
vm_space and page_table continue to take over duties from
page_manager:
- creation and deletion of address spaces / pml4s
- cross-address-space copies for endpoints
- taking over pml4 ownership from process
Also fixed the bug where the wrong process was being set in the cpu
data.
To solve: now the kernel process has its own vm_space which is not
g_kernel_space.
Replace linearly-indexed vector of handles with new kutil::map. Also
provide thread::current() and process::current() accessors so that every
syscall doesn't need to include the scheduler to deduce the current
process.
Renamed and genericized the stack_cache class to manage any address
range area of buffers or memory regions. Removed singleton and created
some globals that map to different address regions (kernel stacks,
kernel buffers).
Tags: vmem virtual memeory
When committing an area of vmem and splitting from a larger block, the
block that is returned was set to the unknown state, and the leading
block was incorrectly set to the desired state.
Also remove extra unused thread ctor.
We were previously allocating kernel stacks as large objects on the
heap. Now keep track of areas of the kernel stack area that are in use,
and allocate them from there. Also required actually implementing
vm_space::commit(). This still needs more work.
Implement the syscalls necessary for threads to create other threads in
their same process. This involved rearranging a number of syscalls, as
well as implementing object_wait and a basic implementation of a
process' list of handles.
The TCB is always stored at a constant offset within the thread object.
So instead of carrying an extra pointer, just implement thread::from_tcb
to get the thread.
Re-implent the concept of processes as separate from threads, and as a
kobject API object. Also improve scheduler::prune which was doing some
unnecessary iterations.
