Module sunrise_bootstrap::frame_alloc

A module implementing a physical memory manager that allocates and frees memory frames

We define a frame as the same size as a page, to make things easy for us. This module can only allocate and free whole frames.

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, MMIO or simply because our kernel is loaded in it

Structs

AllocatorBitmap	A big bitmap denoting for every frame if it is free or not
Frame	A pointer to a physical frame
FrameAllocator	A physical memory manger to allocate and free memory frames

Constants

FRAMES_BITMAP_SIZE	When testing we use a much smaller array.
FRAME_BASE_LOG
FRAME_BASE_MASK
FRAME_FREE
FRAME_OCCUPIED
FRAME_OFFSET_MASK
MEMORY_FRAME_SIZE	A memory frame is the same size as a page

Statics

FRAMES_BITMAP

A big bitmap denoting for every frame if it is free or not

Functions

addr_to_frame	Gets the frame number from a physical address
frame_to_addr	Gets the physical address from a frame number
round_to_page	Rounds an address to its page address
round_to_page_upper	Rounds an address to the next page address except if its offset in that page is 0