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.
This change finally adds capabilities to handles. Included changes:
- j6_handle_t is now again 64 bits, with the highest 8 bits being a type
code, and the next highest 24 bits being the capability mask, so that
programs can check type/caps without calling the kernel.
- The definitions grammar now includes a `capabilities [ ]` section on
objects, to list what capabilities are relevant.
- j6/caps.h is auto-generated from object capability lists
- init_libj6 again sets __handle_self and __handle_sys, this is a bit
of a hack.
- A new syscall, j6_handle_list, will return the list of existing
handles owned by the calling process.
- syscall_verify.cpp.cog now actually checks that the needed
capabilities exist on handles before allowing the call.
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.
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 vm_area objects had a number of issues I have been running into when
working on srv.init:
- It was impossible to map a VMA, fill it, unmap it, and hand it to
another process. Unmapping the VMA in this process would cause all the
pages to be freed, since it was removed from its last mapping.
- If a VMA was marked with vm_flag::zero, it would be zeroed out _every
time_ it was mapped into a vm_space.
- The vm_area_open class was leaking its page_tree nodes.
In order to fix these issues, the different VMA types all work slightly
differently now:
- Physical pages allocated for a VMA are now freed when the VMA is
deleted, not when it is unmapped.
- A knock-on effect from the first point is that vm_area_guarded is now
based on vm_area_open, instead of vm_area_untracked. An untracked area
cannot free its pages, since it does not track them.
- The vm_area_open type now deletes its root page_tree node. And
page_tree nodes will delete child nodes or free physical pages in
their dtors.
- vm_flag::zero has been removed; pages will need to be zeroed out
further at a higher level.
- vm_area also no longer deletes itself only on losing its last handle -
it will only self-delete when all handles _and_ mappings are gone.
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.
Pull this widely-useful header out of kutil, so more things can use it.
Also replace its dependency on <type_traits> by defining our own custom
basic_types.h which contains a subset of the standard's types.
Create a new usermode program, srv.init, and have it read the initial
module_page args sent to it by the bootloader. Doesn't yet do anything
useful but sets up the way for loading the rest of the programs from
srv.init.
Other (mostly) related changes:
- bootloader: The allocator now has a function for allocating init
modules out of a modules_page slab. Also changed how the allocator is
initialized and passes the allocation register and modules_page list
to efi_main().
- bootloader: Expose the simple wstrlen() to the rest of the program
- bootloader: Move check_cpu_supported() to hardware.cpp
- bootloader: Moved program_desc to loader.h and made the loader
functions take it as an argument instead of paths.
- kernel: Rename the system_map_mmio syscall to system_map_phys, and
stop having it default those VMAs to having the vm_flags::mmio flag.
Added a new flag mask, vm_flags::driver_mask, so that drivers can be
allowed to ask for the MMIO flag.
- kernel: Rename load_simple_process() to load_init_server() and got rid
of all the stack setup routines in memory_bootstrap.cpp and task.s
- Fixed formatting in config/debug.toml, undefined __linux and other
linux-specific defines, and got rid of _LIBCPP_HAS_THREAD_API_EXTERNAL
because that's just not true.
Changing the SFINAE/enable_if strategy from a type to a constexpr
function means that it can be defined in other scopes than the functions
themselves, because of function overloading. This lets us put everything
into the kutil::bitfields namespace, and make bitfields out of enums in
other namespaces. Also took the chance to clean up the implementation a
bit.
Create a syscall for drivers to be able to ask the kernel for a VMA that
maps a MMIO area. Also expose vm_flags via j6 table style include file
and new flags.h header.
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.
Several changes were needed to make this work:
- Update the page_table::flags to understand memory caching types
- Set up the PAT MSR to add the WC option
- Make page-offset area mapped as WT
- Add all the MTRR and PAT MSRs, and log the MTRRs for verification
- Add a vm_area flag for write_combining
Create a new framebuffer driver. Also hackily passing frame buffer size
in the list of init handles to all processes and mapping the framebuffer
into all processes. Changed bootloader passing frame buffer as a module
to its own struct.
The vm_area_shared type of VMA used to track mappings in a separate
array, which doubled information and wasted space. This was no longer
used, and is now removed.
The vm_space allow() functionality was a bit janky; using VMAs for all
regions would be a lot cleaner. To that end, this change:
- Adds a "static array" ctor to kutil::vector for setting the kernel
address space's VMA list. This way a kernel heap VMA can be created
without the heap already existing.
- Splits vm_area into different subclasses depending on desired behavior
- Splits out the concept of vm_mapper which maps vm_areas to vm_spaces,
so that some kinds of VMA can be inherently single-space
- Implements VMA resizing so that userspace can grow allocations.
- Obsolete page_table_indices is removed
Also, the following bugs were fixed:
- kutil::map iterators on empty maps no longer break
- memory::page_count was doing page-align, not page-count
See: Github bug #242
See: [frobozz blog post](https://jsix.dev/posts/frobozz/)
Tags:
Finished the VMA kobject and added the related syscalls. Processes can
now allocate memory! Other changes in this commit:
- stop using g_frame_allocator and add frame_allocator::get()
- make sure to release all handles in the process dtor
- fix kutil::map::iterator never comparing to end()
Added the syscalls/helpers.h file to templatize common kobject syscall
operations. Also moved most syscall implementations to using
process::current() and thread::current() instead of asking the
scheduler.
This is the first commit of several reworking the VM system. The main
focus is replacing page_manager's global functionality with objects
representing individual VM spaces. The main changes in this commit were:
- Adding the (as yet unused) vm_area object, which will be the main
point of control for programs to allocate or share memory.
- Replace the old vm_space with a new one based on state in its page
tables. They will also be containers for vm_areas.
- vm_space takes over from page_manager as the page fault handler
- Commented out the page walking in memory_bootstrap; I'll probably need
to recreate this functionality, but it was broken as it was.
- Split out the page_table.h implementations from page_manager.cpp into
the new page_table.cpp, updated it, and added page_table::iterator as
well.
