0ctobyte/popcorn

A 64-bit kernel for ARMv8-A CPU's.

popcorn's Issues

Use spinlocks in data structures

Specifically in pmm.c, instead of using INTERRUPT_LOCK, use a spinlock in the pagestack data structure

Spinlocks should be used in the data structures in pmap.c, vmm.c, vsprintf.c, etc.

Documentation on how to load and run on the Beaglebone Black

Use CMake for build system

The Makefile is simple and works for now, but maybe a more flexible build system (CMake) should be used?

Move Beaglebone specific code to platform directory

There is some code in _loader.s that is specific to the Beaglebone Black. This needs to be somewhere in the platform directory

Need a way to allocate 4 contiguous pages aligned to a 16 KiB boundary for PGD

ARM 1st level page table (i.e. page directory) is 16 KiB in size and is required to be 16 KiB aligned. Currently, contiguous physical pages can be allocated using pmm_alloc_contiguous but there is no way to align such an allocation to an address boundary.

Implement pmap_enter

Needed by _vmm_kernel_init (#7) to enter mappings for the kernel virtual memory region.

Lock pmap before modifications

Kernel can be interrupted when modifying pmaps thus leaving them in an undetermined state. Use a lock to prevent this.

Implement kheap: Buddy allocation

Implement a kernel heap memory manager based on the buddy allocation algorithm. Need to complete #7 first.

Initialize the kernel's virtual memory map (vmm)

The kernel heap will use the kernel_vmap structure to find the location of the start of the kernel heap

pmap_destroy doesn't deallocate resources when the pmap's refcount is zero

pmap_destroy should deallocate a pmap's resources when the refcount becomes zero. This functionality depends on the slab allocator (and thus the kernel heap) being implemented. Marked as incomplete for now.

Add pmm_reserve_page function

Use to mark certain pages as used. This needs to be used to mark kernel pages (and devices addresses) as used on kernel startup.

File 'disk1.img' is missing

kernel.img can be built successfully from source, but there seems to be no file disk1.img found when I attempt to execute tools/sim.sh. Here are the error messages:

qemu-system-arm: -hda disk1.img: could not open disk image disk1.img: Could not open 'disk1.img': No such file or directory

uart0.c: incorrect use UARTFR register offset

The register offset value is added to a pointer type, this will result in an incorrect register access