areas.c File Reference

This file contains functions for manipulating regions of virtual memory known as areas. More...

Functions
void	list_areas (MemContext_s *psCtx)
	Prints all areas in the specified memory context to the debug console.
void	validate_kernel_pages (void)
status_t	put_area (MemArea_s *psArea)
status_t	alloc_area_list (uint32_t nProtection, uint32_t nLockMode, uintptr_t nAddress, uint_fast32_t nCount, const char *const *apzNames, size_t *panOffsets, size_t *panSizes, area_id *panAreas)
	Allocates an array of areas with the specified names, starting offsets and sizes.
status_t	resize_area (area_id hArea, size_t nNewSize, bool bAtomic)
	Resizes the specified area.
status_t	delete_area (area_id hArea)
	Deletes the specified area.
void	empty_mem_context (MemContext_s *psCtx)
	Deletes all areas in the specified memory context.
void	delete_mem_context (MemContext_s *psCtx)
	Deletes the specified memory context and all of its areas.
status_t	clone_page_pte (pte_t *pDst, pte_t *pSrc, bool bCow)
	Copies a page-table entry, optionally setting up copy-on-write semantics.
MemContext_s *	clone_mem_context (MemContext_s *psOrig)
	Clones the specified memory context.
status_t	map_area_to_file (area_id hArea, File_s *psFile, flags_t nProtection __attribute__((unused)), off_t nOffset, size_t nSize)
	Maps the specified area onto a file.
area_id	sys_clone_area (const char *pzName, void **ppAddress, flags_t nProtection, flags_t nLockMode, area_id hSrcArea)
	Clones the specified area at a new address.
area_id	create_area (const char *pzName, void **ppAddress, size_t nSize, size_t nMaxSize, flags_t nProtection, flags_t nLockMode)
	Creates a new memory area in the current process.
area_id	sys_create_area (const char *pzName, void **ppAddress, size_t nSize, flags_t nProtection, flags_t nLockMode)
	Creates a new memory area with the specified attributes.
status_t	sys_delete_area (area_id hArea)
	Deletes the specified area.
status_t	get_area_physical_address (area_id hArea, uintptr_t *pnAddress)
	Returns the starting physical memory address for the specified area.
status_t	get_area_info (area_id hArea, AreaInfo_s *psInfo)
	Returns an AreaInfo_s for the specified area.
status_t	sys_get_area_info (area_id hArea, AreaInfo_s *psInfo)
	Returns an AreaInfo_s for the specified area.
status_t	sys_remap_area (area_id hArea, void *pPhysAddress)
	Remaps the specified area to use a different region of physical memory.
status_t	remap_area (area_id hArea, void *pPhysAddress)
	Remaps the specified area to use a different region of physical memory.
status_t	memcpy_to_user (void *pDst, const void *pSrc, size_t nSize)
	Copies a region of memory from kernel space into user space.
status_t	memcpy_from_user (void *pDst, const void *pSrc, size_t nSize)
	Copies a region of memory from user space into kernel space.
status_t	strncpy_from_user (char *pzDst, const char *pzSrc, size_t nMaxLen)
	Copies a string from user space into kernel space.
status_t	strndup_from_user (const char *pzSrc, size_t nMaxLen, char **ppzDst)
	Copies a string from user space into a newly allocated kernel region.
status_t	strcpy_to_user (char *pzDst, const char *pzSrc)
	Copies a string from kernel space into user space.
status_t	strlen_from_user (const char *pzString)
	Returns the length of the specified string.
status_t	verify_mem_area (const void *pAddress, size_t nSize, bool bWriteAccess)
	Verifies a region of user memory for kernel access.
void *	sys_sbrk (int nDelta)
	Adjusts the upper bound of a user process's data segment.
area_id	clone_from_inactive_ctx (MemArea_s *psArea, uintptr_t nOffset, size_t nLength)
	clone_from_inactive_ctx() and update_inactive_ctx() are used to access an inactive address space / memory context (the associated process is not currently running, page directory is not loaded into CR3).
status_t	update_inactive_ctx (MemArea_s *psOriginalArea, area_id hCloneArea, uintptr_t nOffset)
	See also: clone_from_inactive_ctx()
void	init_kernel_mem_context ()
	Creates the memory context for the kernel.
void	init_areas (void)
	Initializes the area manager.
Variables
MultiArray_s	g_sAreas
	A private shared MultiArray for managing areas.
sem_id	g_hAreaTableSema = -1
	A semaphore to control access to g_sAreas.

---

Detailed Description

This file contains functions for manipulating regions of virtual memory known as areas.

An area can exist in one of several states depending on its access privileges and whether or not it is currently located in physical memory.

Read only:

Both the area and the PTE are marked read only.

Cloned as copy-on-write:

The PTE is marked as read-only and the area is marked as read-write.

Memory mapped/not present:

The area has a non-NULL a_psFile entry and the PTE has the value 0.

Memory mapped/present:

The area has a non-NULL a_psFile entry and the PTE is marked present.

Shared/not-present:

The area has the AREA_SHARED flag set and the PTE is marked not present.

Swapped out:

The PTE is marked not-present but the address is non-null.

---

Function Documentation

area_id clone_from_inactive_ctx	(	MemArea_s *	psArea,
		uintptr_t	nOffset,
		size_t	nLength
	)

clone_from_inactive_ctx() and update_inactive_ctx() are used to access an inactive address space / memory context (the associated process is not currently running, page directory is not loaded into CR3).

clone_from_inactive_ctx() will create in kernel space a clone of (a part of) the specified area. If you have written to the cloned area, call update_inactive_ctx() to make sure that pages allocated by the copy-on-write mechanism are transfered to the originating memory context.

void init_kernel_mem_context

(

void

)

Creates the memory context for the kernel.

This context holds all kernel areas below AREA_FIRST_USER_ADDRESS.

area_id sys_clone_area	(	const char *	pzName,
		void **	ppAddress,
		flags_t	nProtection,
		flags_t	nLockMode,
		area_id	hSrcArea
	)

Clones the specified area at a new address.

Parameters:

	pzName	a pointer to the string containing the name of the new area.
	ppAddress	a pointer to the variable where the start address of the new area will be stored, or NULL. If non- NULL, the previous value of the variable it points to will be used as the preferred start address of the new area.
	nProtection	a protection bitmask containing any combination of: AREA_READ, AREA_WRITE, AREA_EXEC, AREA_KERNEL, and AREA_WRCOMB.
	nLockMode	the locking mode to use: AREA_NO_LOCK, AREA_LAZY_LOCK, AREA_FULL_LOCK, or AREA_CONTIGUOUS.
	hSrcArea	the area_id of the area to clone.

Returns:

-EFAULT if there is a memory access violation while copying pzName; -EINVAL if the preferred starting address at *ppAddress is not a multiple of PAGE_SIZE; the area_id of the new area otherwise.

See also:

alloc_area()

Author:

Kurt Skauen ([email protected])

area_id sys_create_area	(	const char *	pzName,
		void **	ppAddress,
		size_t	nSize,
		flags_t	nProtection,
		flags_t	nLockMode
	)

Creates a new memory area with the specified attributes.

Parameters:

	pzName	a pointer to the string containing the name for the new area.
	ppAddress	a pointer to the variable where the start address of the new area will be stored, or NULL. If non- NULL, the previous value of the variable it points to will be used as the preferred start address of the new area.
	nSize	the size in bytes of the requested area.
	nProtection	a protection bitmask containing any combination of AREA_READ, AREA_WRITE, AREA_EXEC, AREA_KERNEL, and AREA_WRCOMB.
	nLockMode	the locking mode to use: AREA_NO_LOCK, AREA_LAZY_LOCK, AREA_FULL_LOCK, or AREA_CONTIGUOUS.

Returns:

-EFAULT if there is a memory access violation while copying pzName; -EINVAL if the preferred start address at *ppAddress is not a multiple of PAGE_SIZE; -ENOADDRSPC if there isn't enough virtual address space, -ENOMEM if there isn't enough physical memory; the area_id of the new area otherwise.

See also:

alloc_area(), do_create_area()

Author:

Kurt Skauen ([email protected])

status_t sys_delete_area

(

area_id

hArea

)

Deletes the specified area.

Parameters:

hArea

a handle to the area to delete.

Returns:

-EINVAL if the area handle is invalid or if the area doesn't belong to this process; 0 otherwise.

See also:

do_delete_area()

Author:

Kurt Skauen ([email protected])

status_t sys_get_area_info	(	area_id	hArea,
		AreaInfo_s *	psInfo
	)

Returns an AreaInfo_s for the specified area.

Parameters:

	hArea	a handle to the area for which to return info.
	psInfo	a pointer to the AreaInfo_s in which to store the results.

Returns:

-EINVAL if the area handle is invalid or the area doesn't belong to this process; -EFAULT if there is a memory access violation while copying to psInfo; 0 otherwise.

Author:

Kurt Skauen ([email protected])

status_t sys_remap_area	(	area_id	hArea,
		void *	pPhysAddress
	)

Remaps the specified area to use a different region of physical memory.

Parameters:

	hArea	a handle to the area to remap.
	pPhysAddress	the new start address in physical memory for the region.

Returns:

-EINVAL if the area handle is invalid or if nPhysAddress isn't a multiple of PAGE_SIZE; 0 otherwise.

See also:

do_remap_area()

Author:

Kurt Skauen ([email protected])

void* sys_sbrk

(

int

nDelta

)

Adjusts the upper bound of a user process's data segment.

Parameters:

nDelta

the number of bytes by which to increase or decrease the data segment.

Returns:

-1 if there was an error adjusting the data segment; otherwise, the old upper bound of the process's data segment.

Author:

Kurt Skauen ([email protected])

---