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.
We started actually running up against the page boundary for kernel
stacks and thus double-faulting on page faults from kernel space. So I
finally added IST stacks. Note that we currently just
increment/decrement the IST entry by a page when we enter the handler to
avoid clobbering on re-entry, but this means:
* these handlers need to be able to operate with only a page of stack
* kernel stacks always have to be >1 pages
* the amount of nesting possible is tied to the kernel stack size.
These seem fine for now, but we should maybe find a way to use something
besides g_kernel_stacks to set up the IST stacks if/when this becomes an
issue.
The previous frame allocator involved a lot of splitting and merging
linked lists and lost all information about frames while they were
allocated. The new allocator is based on an array of descriptor
structures and a bitmap. Each memory map region of allocatable memory
becomes one or more descriptors, each mapping up to 1GiB of physical
memory. The descriptors implement two levels of a bitmap tree, and have
a pointer into the large contiguous bitmap to track individual pages.
To enable setting sections as NX or read-only, the boot program loader
now loads programs as lists of sections, and the kernel args are updated
accordingly. The kernel's loader now just takes a program pointer to
iterate the sections. Also enable NX in IA32_EFER in the bootloader.
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:
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.
Multiple changes regarding channels. Mainly channels are now stream
based and can handle partial reads or writes. Channels now use the
kernel buffers area with the related buffer_cache. Added a fake stdout
stream channel and kernel task to read its contents to the screen in
preparation for handing channels as stdin/stdout to processes.
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.
There were a few lingering bugs due to places where 510/511 were
hard-coded as the kernel-space PML4 entries. These are now constants
defined in kernel_memory.h instead.
Tags: boot memory paging
The `kernel_offset` and `page_offset` had already been updated with
previous bootloader changes, but `kernel_max_heap` had not. Also, make
all the constants `constexpr` instead of `static const` that would live
in multiple TUs.
This commit makes several fundamental changes to memory handling:
- the frame allocator is now only an allocator for free frames, and does
not track used frames.
- the frame allocator now stores its free list inside the free frames
themselves, as a hybrid stack/span model.
- This has the implication that all frames must currently fit within
the offset area.
- kutil has a new allocator interface, which is the only allowed way for
any code outside of src/kernel to allocate. Code under src/kernel
_may_ use new/delete, but should prefer the allocator interface.
- the heap manager has become heap_allocator, which is merely an
implementation of kutil::allocator which doles out sections of a given
address range.
- the heap manager now only writes block headers when necessary,
avoiding page faults until they're actually needed
- page_manager now has a page fault handler, which checks with the
address_manager to see if the address is known, and provides a frame
mapping if it is, allowing heap manager to work with its entire
address size from the start. (Currently 32GiB.)
Additionally, there were several bug fixes needed to allow this:
- frame_allocator was allocating its frame_blocks from the heap, causing
a circular dependency. Now it gives itself a page on its own when
needed.
- frame_allocator::free was putting any trailing pages in a block back
into the list after the current block, so they would be the next block
iterated to.
- frame_allocator::free was updating the address it was looking for
after freeing some pages, but not the count it was looking for, so it
would eventually free all pages after the initial address.
