Implementation of the Zone Allocator. More...

Classes
struct	page_t
	Page descriptor. Use as a bitmap to understand the order of the block and if it is free or allocated. More...

struct	zone_t
	Data structure to differentiate memory zone. More...

struct	pg_data_t
	Data structure to rapresent a memory node. In Uniform memory access (UMA) architectures there is only one node called contig_page_data. More...

Macros
#define	page_count(p) atomic_read(&(p)->count)
	Reads the page count.

#define	set_page_count(p, v) atomic_set(&(p)->count, v)
	Sets the page count.

#define	page_inc(p) atomic_inc(&(p)->count)
	Increments the counter for the given page.

#define	page_dec(p) atomic_dec(&(p)->count)
	Decrements the counter for the given page.

Typedefs
typedef struct page_t	page_t
	Page descriptor. Use as a bitmap to understand the order of the block and if it is free or allocated.

typedef struct zone_t	zone_t
	Data structure to differentiate memory zone.

typedef struct pg_data_t	pg_data_t
	Data structure to rapresent a memory node. In Uniform memory access (UMA) architectures there is only one node called contig_page_data.

Enumerations
enum	zone_type { ZONE_NORMAL , ZONE_HIGHMEM , __MAX_NR_ZONES }
	Enumeration for zone_t. More...

Functions
uint32_t	find_nearest_order_greater (uint32_t base_addr, uint32_t amount)
	Finds the nearest order of memory allocation that can accommodate a given amount of memory. More...

int	pmmngr_init (boot_info_t *boot_info)
	Physical memory manager initialization. More...

page_t *	alloc_page_cached (gfp_t gfp_mask)
	Allocates a cached page based on the given GFP mask. More...

int	free_page_cached (page_t *page)
	Free a page allocated with alloc_page_cached. More...

uint32_t	__alloc_page_lowmem (gfp_t gfp_mask)
	Find the first free page frame, set it allocated and return the memory address of the page frame. More...

int	free_page_lowmem (uint32_t addr)
	Frees the given page frame address. More...

uint32_t	__alloc_pages_lowmem (gfp_t gfp_mask, uint32_t order)
	Find the first free 2^order amount of page frames, set it allocated and return the memory address of the first page frame allocated. More...

page_t *	_alloc_pages (gfp_t gfp_mask, uint32_t order)
	Find the first free 2^order amount of page frames, set it allocated and return the memory address of the first page frame allocated. More...

uint32_t	get_virtual_address_from_page (page_t *page)
	Converts a page structure to its corresponding low memory virtual address. More...

uint32_t	get_physical_address_from_page (page_t *page)
	Converts a page structure to its corresponding physical address. More...

page_t *	get_page_from_physical_address (uint32_t paddr)
	Retrieves the page structure corresponding to a given physical address. More...

page_t *	get_page_from_virtual_address (uint32_t vaddr)
	Retrieves the low memory page corresponding to the given virtual address. More...

int	free_pages_lowmem (uint32_t addr)
	Frees from the given page frame address up to 2^order amount of page frames. More...

int	__free_pages (page_t *page)
	Frees from the given page frame address up to 2^order amount of page frames. More...

unsigned long	get_zone_total_space (gfp_t gfp_mask)
	Retrieves the total space of the zone corresponding to the given GFP mask. More...

unsigned long	get_zone_free_space (gfp_t gfp_mask)
	Retrieves the free space of the zone corresponding to the given GFP mask. More...

unsigned long	get_zone_cached_space (gfp_t gfp_mask)
	Retrieves the cached space of the zone corresponding to the given GFP mask. More...

static int	is_lowmem_page_struct (void *addr)
	Checks if the specified address points to a page_t (or field) that belongs to lowmem. More...

Variables
page_t *	mem_map
	Array of all physical memory blocks (pages). More...

pg_data_t *	contig_page_data
	Memory node descriptor for contiguous memory. More...

Detailed Description

Implementation of the Zone Allocator.

Copyright: (c) 2014-2024 This file is distributed under the MIT License. See LICENSE.md for details.

Enumeration Type Documentation

◆ zone_type

enum zone_type

Enumeration for zone_t.

Enumerator

ZONE_NORMAL

Direct mapping. Used by the kernel.

Normal addressable memory is in ZONE_NORMAL. DMA operations can be performed on pages in ZONE_NORMAL if the DMA devices support transfers to all addressable memory.

ZONE_HIGHMEM

Page tables mapping. Used by user processes.

A memory area that is only addressable by the kernel through mapping portions into its own address space. This is for example used by i386 to allow the kernel to address the memory beyond 900MB. The kernel will set up special mappings (page table entries on i386) for each page that the kernel needs to access.

__MAX_NR_ZONES

The maximum number of zones.

Function Documentation

◆ __alloc_page_lowmem()

uint32_t __alloc_page_lowmem ( gfp_t gfp_mask )

Find the first free page frame, set it allocated and return the memory address of the page frame.

Parameters

gfp_mask GFP_FLAGS to decide the zone allocation.

Returns: The low memory address of the allocated page, or 0 if allocation fails.

◆ __alloc_pages_lowmem()

uint32_t __alloc_pages_lowmem	(	gfp_t	gfp_mask,
		uint32_t	order
	)

Find the first free 2^order amount of page frames, set it allocated and return the memory address of the first page frame allocated.

Parameters

gfp_mask	GFP_FLAGS to decide the zone allocation.
order	The logarithm of the size of the page frame.

Returns: Memory address of the first free page frame allocated.

◆ __free_pages()

int __free_pages ( page_t * page )

Frees from the given page frame address up to 2^order amount of page frames.

Parameters

page The page.

Returns: Returns 0 on success, or -1 if an error occurs.

◆ _alloc_pages()

page_t* _alloc_pages	(	gfp_t	gfp_mask,
		uint32_t	order
	)

Find the first free 2^order amount of page frames, set it allocated and return the memory address of the first page frame allocated.

Parameters

gfp_mask	GFP_FLAGS to decide the zone allocation.
order	The logarithm of the size of the page frame.

Returns: Memory address of the first free page frame allocated, or NULL if allocation fails.

◆ alloc_page_cached()

page_t* alloc_page_cached ( gfp_t gfp_mask )

Allocates a cached page based on the given GFP mask.

Parameters

gfp_mask The GFP mask specifying the allocation constraints.

Returns: A pointer to the allocated page, or NULL if allocation fails.

◆ find_nearest_order_greater()

uint32_t find_nearest_order_greater	(	uint32_t	base_addr,
		uint32_t	amount
	)

Finds the nearest order of memory allocation that can accommodate a given amount of memory.

Parameters

base_addr	the base address from which to calculate the number of pages.
amount	the amount of memory (in bytes) to allocate.

Returns: The nearest order (power of two) that is greater than or equal to the number of pages required.

◆ free_page_cached()

int free_page_cached ( page_t * page )

Free a page allocated with alloc_page_cached.

Parameters

page	Pointer to the page to free.

Returns: Returns 0 on success, or -1 if an error occurs.

◆ free_page_lowmem()

int free_page_lowmem ( uint32_t addr )

Frees the given page frame address.

Parameters

addr	The block address.

Returns: Returns 0 on success, or -1 if an error occurs.

◆ free_pages_lowmem()

int free_pages_lowmem ( uint32_t addr )

Frees from the given page frame address up to 2^order amount of page frames.

Parameters

addr	The page frame address.

Returns: Returns 0 on success, or -1 if an error occurs.

◆ get_page_from_physical_address()

page_t* get_page_from_physical_address ( uint32_t paddr )

Retrieves the page structure corresponding to a given physical address.

Parameters

paddr The physical address for which the page structure is requested.

Returns: A pointer to the corresponding page structure, or NULL if the address is invalid.

◆ get_page_from_virtual_address()

page_t* get_page_from_virtual_address ( uint32_t vaddr )

Retrieves the low memory page corresponding to the given virtual address.

Parameters

vaddr the virtual address to convert.

Returns: A pointer to the corresponding page, or NULL if the address is out of range.

◆ get_physical_address_from_page()

uint32_t get_physical_address_from_page ( page_t * page )

Converts a page structure to its corresponding physical address.

Parameters

page	Pointer to the page structure.

Returns: The physical address corresponding to the specified page, or 0 if the input page pointer is invalid.

◆ get_virtual_address_from_page()

uint32_t get_virtual_address_from_page ( page_t * page )

Converts a page structure to its corresponding low memory virtual address.

Parameters

page	Pointer to the page structure.

Returns: The low memory virtual address corresponding to the specified page, or 0 if the input page pointer is invalid.

◆ get_zone_cached_space()

unsigned long get_zone_cached_space ( gfp_t gfp_mask )

Retrieves the cached space of the zone corresponding to the given GFP mask.

Parameters

gfp_mask The GFP mask specifying the allocation constraints.

Returns: The cached space of the zone, or 0 if the zone cannot be retrieved.

◆ get_zone_free_space()

unsigned long get_zone_free_space ( gfp_t gfp_mask )

Retrieves the free space of the zone corresponding to the given GFP mask.

Parameters

gfp_mask The GFP mask specifying the allocation constraints.

Returns: The free space of the zone, or 0 if the zone cannot be retrieved.

◆ get_zone_total_space()

unsigned long get_zone_total_space ( gfp_t gfp_mask )

Retrieves the total space of the zone corresponding to the given GFP mask.

Parameters

gfp_mask The GFP mask specifying the allocation constraints.

Returns: The total space of the zone, or 0 if the zone cannot be retrieved.

◆ is_lowmem_page_struct()

static int is_lowmem_page_struct ( void * addr )

inlinestatic

Checks if the specified address points to a page_t (or field) that belongs to lowmem.

Parameters

addr	The address to check.

Returns: 1 if it belongs to lowmem, 0 otherwise.

◆ pmmngr_init()

int pmmngr_init ( boot_info_t * boot_info )

Physical memory manager initialization.

Parameters

boot_info Information coming from the booloader.

Returns: Outcome of the operation.

Variable Documentation

◆ contig_page_data

pg_data_t* contig_page_data

extern

Memory node descriptor for contiguous memory.

This variable points to the pg_data_t structure, which represents a memory node (usually for NUMA systems). It typically describes the memory properties and zones for a contiguous block of physical memory.

◆ mem_map

page_t* mem_map

extern

Array of all physical memory blocks (pages).

This variable points to an array of page_t structures representing all physical memory blocks (pages) in the system. It is used to track the state of each page in memory.

Classes

Macros

Typedefs

Enumerations

Functions

Variables

Detailed Description

Enumeration Type Documentation

◆ zone_type

Function Documentation

◆ __alloc_page_lowmem()

◆ __alloc_pages_lowmem()

◆ __free_pages()

◆ _alloc_pages()

◆ alloc_page_cached()

◆ find_nearest_order_greater()

◆ free_page_cached()

◆ free_page_lowmem()

◆ free_pages_lowmem()

◆ get_page_from_physical_address()

◆ get_page_from_virtual_address()

◆ get_physical_address_from_page()

◆ get_virtual_address_from_page()

◆ get_zone_cached_space()

◆ get_zone_free_space()

◆ get_zone_total_space()

◆ is_lowmem_page_struct()

◆ pmmngr_init()

Variable Documentation

◆ contig_page_data

◆ mem_map