Module sunrise_kernel::frame_allocator::i386

Architecture specific-behaviour i386 implementation of the frame allocator.

It keeps tracks of the allocated frames by mean of a giant bitmap mapping every physical memory frame in the address space to a bit representing if it is free or not. This works because the address space in 32 bits is only 4GB, so ~1 million frames only

During init we initialize the bitmap by parsing the information that the bootloader gives us and marking some physical memory regions as reserved, either because of BIOS or MMIO.

We also reserve everything that is mapped in KernelLand, assuming the bootstrap mapped it there for us, and we don't want to overwrite it.

We do not distinguish between reserved and occupied frames.

Structs

FrameAllocator	The physical memory manager.
FrameAllocatori386	A frame allocator backed up by a giant bitmap.

Constants

FRAMES_BITMAP_SIZE	For unit tests we use a much smaller array.
FRAME_BASE_LOG	The right shift to perform to a Physical address to get its frame id.
FRAME_BASE_MASK	The frame part in PhysicalAddress.
FRAME_FREE	In the the bitmap, 1 means the frame is free.
FRAME_OCCUPIED	In the the bitmap, 0 means the frame is occupied.
FRAME_OFFSET_MASK	The offset part in a PhysicalAddress.

Statics

FRAME_ALLOCATOR

A physical memory manger to allocate and free memory frames

Functions

addr_to_frame	Gets the frame number from a physical address
frame_to_addr	Gets the physical address from a frame number
init	Initialize the FrameAllocator by parsing the multiboot information and marking some memory areas as unusable
mark_area_free	Marks a physical memory area as free for frame allocation
mark_area_reserved	Marks a physical memory area as reserved and will never give it when requesting a frame. This is used to mark where memory holes are, or where the kernel was mapped
mark_frame_bootstrap_allocated	Marks a physical memory frame as already allocated Currently used during init when paging marks KernelLand frames as alloc'ed by bootstrap