Implementation of a memory paging management. More...

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Classes
struct	page_dir_entry_t
	An entry of a page directory. More...

struct	page_table_entry_t
	An entry of a page table. More...

struct	page_table_t
	A page table. More...

struct	page_directory_t
	A page directory. More...

struct	vm_area_struct_t
	Virtual Memory Area, used to store details of a process segment. More...

struct	mm_struct_t
	Memory Descriptor, used to store details about the memory of a user process. More...

Macros
#define	PAGE_SHIFT 12
	4KB pages (2^12 = 4096 bytes)

#define	PAGE_SIZE (1 << PAGE_SHIFT)
	Size of a page (4096 bytes).

#define	MAX_PHY_PFN (1UL << (32 - PAGE_SHIFT))
	Maximum number of physical page frame numbers (PFNs).

#define	PROCAREA_START_ADDR 0x00000000
	The start of the process area.

#define	PROCAREA_END_ADDR 0xC0000000
	The end of the process area (and start of the kernel area).

#define	MAX_PAGE_TABLE_ENTRIES 1024
	For a single page table in a 32-bit system.

#define	MAX_PAGE_DIR_ENTRIES 1024
	For a page directory with 1024 entries.

Typedefs
typedef struct page_dir_entry_t	page_dir_entry_t
	An entry of a page directory.

typedef struct page_table_entry_t	page_table_entry_t
	An entry of a page table.

typedef struct page_table_t	_syscall0 = _syscall0( (aligned( (1 << 12 ) )) )= _syscall1( (aligned( (1 << 12 ) )) )= _syscall2( (aligned( (1 << 12 ) )) )= _syscall3( (aligned( (1 << 12 ) )) )= page_table_t
	A page table. More...

typedef struct vm_area_struct_t	vm_area_struct_t
	Virtual Memory Area, used to store details of a process segment.

typedef struct mm_struct_t	mm_struct_t
	Memory Descriptor, used to store details about the memory of a user process.

Enumerations
enum	MEMMAP_FLAGS { MM_USER = 0x1 , MM_GLOBAL = 0x2 , MM_RW = 0x4 , MM_PRESENT = 0x8 , MM_COW = 0x10 , MM_UPDADDR = 0x20 }
	Flags associated with virtual memory areas. More...

Functions
static int	vm_area_compare (const list_head vma0, const list_head vma1)
	Comparison function between virtual memory areas. More...

int	paging_init (boot_info_t *info)
	Initializes the paging system, sets up memory caches, page directories, and maps important memory regions. More...

page_directory_t *	paging_get_main_directory (void)
	Provide access to the main page directory. More...

static page_directory_t *	paging_get_current_directory (void)
	Provide access to the current paging directory. More...

static void	paging_switch_directory (page_directory_t *dir)
	Switches paging directory, the pointer must be a physical address. More...

int	is_current_pgd (page_directory_t *pgd)
	Checks if the given page directory is the current one. More...

int	paging_switch_directory_va (page_directory_t *dir)
	Switches paging directory, the pointer can be a lowmem address. More...

void	paging_flush_tlb_single (unsigned long addr)
	Invalidate a single tlb page (the one that maps the specified virtual address) More...

static void	paging_enable (void)
	Enables paging.

static int	paging_is_enabled (void)
	Returns if paging is enabled. More...

void	page_fault_handler (pt_regs *f)
	Handles a page fault. More...

page_t *	mem_virtual_to_page (page_directory_t pgdir, uint32_t virt_start, size_t size)
	Maps a virtual address to a corresponding physical page. More...

int	mem_upd_vm_area (page_directory_t *pgd, uint32_t virt_start, uint32_t phy_start, size_t size, uint32_t flags)
	Updates the virtual memory area in a page directory. More...

int	mem_clone_vm_area (page_directory_t src_pgd, page_directory_t dst_pgd, uint32_t src_start, uint32_t dst_start, size_t size, uint32_t flags)
	Clones a range of pages between two distinct page tables. More...

vm_area_struct_t *	create_vm_area (mm_struct_t *mm, uint32_t virt_start, size_t size, uint32_t pgflags, uint32_t gfpflags)
	Create a virtual memory area. More...

uint32_t	clone_vm_area (mm_struct_t mm, vm_area_struct_t area, int cow, uint32_t gfpflags)
	Clone a virtual memory area, using copy on write if specified. More...

int	destroy_vm_area (mm_struct_t mm, vm_area_struct_t area)
	Destroys a virtual memory area. More...

vm_area_struct_t *	find_vm_area (mm_struct_t *mm, uint32_t vm_start)
	Searches for the virtual memory area at the given address. More...

int	is_valid_vm_area (mm_struct_t *mm, uintptr_t vm_start, uintptr_t vm_end)
	Checks if the given virtual memory area range is valid. More...

int	find_free_vm_area (mm_struct_t mm, size_t length, uintptr_t vm_start)
	Searches for an empty spot for a new virtual memory area. More...

mm_struct_t *	create_blank_process_image (size_t stack_size)
	Creates the main memory descriptor. More...

mm_struct_t *	clone_process_image (mm_struct_t *mmp)
	Create a Memory Descriptor. More...

int	destroy_process_image (mm_struct_t *mm)
	Free Memory Descriptor with all the memory segment contained. More...

Variables
kmem_cache_t *	pgtbl_cache
	Cache used to store page tables. More...

Detailed Description

Implementation of a memory paging management.

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

Typedef Documentation

◆ _syscall0

typedef struct page_directory_t _syscall0 = _syscall0( (aligned( (1 << 12 ) )) )= _syscall1( (aligned( (1 << 12 ) )) )= _syscall2( (aligned( (1 << 12 ) )) )= _syscall3( (aligned( (1 << 12 ) )) )= page_table_t

A page table.

A page directory.

It contains 1024 entries which can be addressed by 10 bits (log_2(1024)).

In the two-level paging, this is the first level.

Enumeration Type Documentation

◆ MEMMAP_FLAGS

enum MEMMAP_FLAGS

Flags associated with virtual memory areas.

Enumerator
MM_USER	Area belongs to user mode (accessible by user-level processes).
MM_GLOBAL	Area is global (not flushed from TLB on context switch).
MM_RW	Area has read/write permissions.
MM_PRESENT	Area is present in memory.
MM_COW	Area is copy-on-write (used for forked processes).
MM_UPDADDR	Update address (used for special memory mappings).

Function Documentation

◆ clone_process_image()

mm_struct_t* clone_process_image ( mm_struct_t * mmp )

Create a Memory Descriptor.

Parameters

mmp	The memory map to clone

Returns: The Memory Descriptor created.

◆ clone_vm_area()

uint32_t clone_vm_area	(	mm_struct_t *	mm,
		vm_area_struct_t *	area,
		int	cow,
		uint32_t	gfpflags
	)

Clone a virtual memory area, using copy on write if specified.

Parameters

mm	the memory descriptor which will contain the new segment.
area	the area to clone
cow	whether to use copy-on-write or just copy everything.
gfpflags	the Get Free Pages flags.

Returns: Zero on success.

◆ create_blank_process_image()

mm_struct_t* create_blank_process_image ( size_t stack_size )

Creates the main memory descriptor.

Parameters

stack_size The size of the stack in byte.

Returns: The Memory Descriptor created.

◆ create_vm_area()

vm_area_struct_t* create_vm_area	(	mm_struct_t *	mm,
		uint32_t	virt_start,
		size_t	size,
		uint32_t	pgflags,
		uint32_t	gfpflags
	)

Create a virtual memory area.

Parameters

mm	The memory descriptor which will contain the new segment.
virt_start	The virtual address to map to.
size	The size of the segment.
pgflags	The flags for the new memory area.
gfpflags	The Get Free Pages flags.

Returns: The newly created virtual memory area descriptor.

◆ destroy_process_image()

int destroy_process_image ( mm_struct_t * mm )

Free Memory Descriptor with all the memory segment contained.

Parameters

mm	The Memory Descriptor to free.

Returns: Returns -1 on error, otherwise 0.

◆ destroy_vm_area()

int destroy_vm_area	(	mm_struct_t *	mm,
		vm_area_struct_t *	area
	)

Destroys a virtual memory area.

Parameters

mm	the memory descriptor from which we will destroy the area.
area	the are we want to destroy.

Returns: 0 if the area was destroyed, or -1 if the operation failed.

◆ find_free_vm_area()

int find_free_vm_area	(	mm_struct_t *	mm,
		size_t	length,
		uintptr_t *	vm_start
	)

Searches for an empty spot for a new virtual memory area.

Parameters

mm	the memory descriptor which should contain the new area.
length	the size of the empty spot.
vm_start	where we save the starting address for the new area.

Returns: 0 on success, -1 on error, or 1 if no free area is found.

◆ find_vm_area()

vm_area_struct_t* find_vm_area	(	mm_struct_t *	mm,
		uint32_t	vm_start
	)

Searches for the virtual memory area at the given address.

Parameters

mm	the memory descriptor which should contain the area.
vm_start	the starting address of the area we are looking for.

Returns: a pointer to the area if we found it, NULL otherwise.

◆ is_current_pgd()

int is_current_pgd ( page_directory_t * pgd )

Checks if the given page directory is the current one.

Parameters

pgd	A pointer to the page directory to check.

Returns: 1 if the given page directory is the current one, 0 otherwise.

◆ is_valid_vm_area()

int is_valid_vm_area	(	mm_struct_t *	mm,
		uintptr_t	vm_start,
		uintptr_t	vm_end
	)

Checks if the given virtual memory area range is valid.

Parameters

mm	the memory descriptor which we use to check the range.
vm_start	the starting address of the area.
vm_end	the ending address of the area.

Returns: 1 if it's valid, 0 if it's occupied, -1 if it's outside the memory.

◆ mem_clone_vm_area()

int mem_clone_vm_area	(	page_directory_t *	src_pgd,
		page_directory_t *	dst_pgd,
		uint32_t	src_start,
		uint32_t	dst_start,
		size_t	size,
		uint32_t	flags
	)

Clones a range of pages between two distinct page tables.

Parameters

src_pgd	The source page directory.
dst_pgd	The dest page directory.
src_start	The source virtual address for the clone.
dst_start	The destination virtual address for the clone.
size	The size of the segment.
flags	The flags for the new dst memory range.

Returns: 0 on success, -1 on failure.

◆ mem_upd_vm_area()

int mem_upd_vm_area	(	page_directory_t *	pgd,
		uint32_t	virt_start,
		uint32_t	phy_start,
		size_t	size,
		uint32_t	flags
	)

Updates the virtual memory area in a page directory.

Parameters

pgd	The page directory to update.
virt_start	The starting virtual address to update.
phy_start	The starting physical address to map to the virtual addresses.
size	The size of the memory area to update.
flags	Flags to set for the page table entries.

Returns: 0 on success, or -1 on failure.

◆ mem_virtual_to_page()

page_t* mem_virtual_to_page	(	page_directory_t *	pgdir,
		uint32_t	virt_start,
		size_t *	size
	)

Maps a virtual address to a corresponding physical page.

Parameters

pgdir	The page directory.
virt_start	The starting virtual address to map.
size	Pointer to a size_t variable to store the size of the mapped memory.

Returns: A pointer to the physical page corresponding to the virtual address, or NULL on error.

◆ page_fault_handler()

void page_fault_handler ( pt_regs * f )

Handles a page fault.

Parameters

f	The interrupt stack frame.

◆ paging_flush_tlb_single()

void paging_flush_tlb_single ( unsigned long addr )

Invalidate a single tlb page (the one that maps the specified virtual address)

Parameters

addr	The address of the page table.

◆ paging_get_current_directory()

static page_directory_t* paging_get_current_directory ( void )

inlinestatic

Provide access to the current paging directory.

Returns: A pointer to the current page directory.

◆ paging_get_main_directory()

page_directory_t* paging_get_main_directory ( void )

Provide access to the main page directory.

Returns: A pointer to the main page directory, or NULL if main_mm is not initialized.

◆ paging_init()

int paging_init ( boot_info_t * info )

Initializes the paging system, sets up memory caches, page directories, and maps important memory regions.

Parameters

info	Pointer to the boot information structure, containing kernel addresses and other details.

Returns: 0 on success, -1 on error.

◆ paging_is_enabled()

static int paging_is_enabled ( void )

inlinestatic

Returns if paging is enabled.

Returns: 1 if paging is enables, 0 otherwise.

◆ paging_switch_directory()

static void paging_switch_directory ( page_directory_t * dir )

inlinestatic

Switches paging directory, the pointer must be a physical address.

Parameters

dir	A pointer to the new page directory.

◆ paging_switch_directory_va()

int paging_switch_directory_va ( page_directory_t * dir )

Switches paging directory, the pointer can be a lowmem address.

Parameters

dir	A pointer to the new page directory.

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

◆ vm_area_compare()

static int vm_area_compare	(	const list_head *	vma0,
		const list_head *	vma1
	)

inlinestatic

Comparison function between virtual memory areas.

Parameters

vma0	Pointer to the first vm_area_struct's list_head.
vma1	Pointer to the second vm_area_struct's list_head.

Returns: 1 if vma0 starts after vma1 ends, 0 otherwise.

Variable Documentation

◆ pgtbl_cache

kmem_cache_t* pgtbl_cache

extern

Cache used to store page tables.

Classes

Macros

Typedefs

Enumerations

Functions

Variables

Detailed Description

Typedef Documentation

◆ _syscall0

Enumeration Type Documentation

◆ MEMMAP_FLAGS

Function Documentation

◆ clone_process_image()

◆ clone_vm_area()

◆ create_blank_process_image()

◆ create_vm_area()

◆ destroy_process_image()

◆ destroy_vm_area()

◆ find_free_vm_area()

◆ find_vm_area()

◆ is_current_pgd()

◆ is_valid_vm_area()

◆ mem_clone_vm_area()

◆ mem_upd_vm_area()

◆ mem_virtual_to_page()

◆ page_fault_handler()

◆ paging_flush_tlb_single()

◆ paging_get_current_directory()

◆ paging_get_main_directory()

◆ paging_init()

◆ paging_is_enabled()

◆ paging_switch_directory()

◆ paging_switch_directory_va()

◆ vm_area_compare()

Variable Documentation

◆ pgtbl_cache