MemoryPageOverlay Class Reference

Memory bank that overlays some other memory bank, using a "copy on write" behavior. More...

#include <memstate.hh>

Inheritance diagram for MemoryPageOverlay:

Public Member Functions
	MemoryPageOverlay (AddrSpace *spc, int4 ws, int4 ps, MemoryBank *ul)
	Constructor for page overlay. More...
Public Member Functions inherited from MemoryBank
	MemoryBank (AddrSpace *spc, int4 ws, int4 ps)
	Generic constructor for a memory bank. More...
int4	getWordSize (void) const
	Get the number of bytes in a word for this memory bank. More...
int4	getPageSize (void) const
	Get the number of bytes in a page for this memory bank. More...
AddrSpace *	getSpace (void) const
	Get the address space associated with this memory bank. More...
void	setValue (uintb offset, int4 size, uintb val)
	Set the value of a (small) range of bytes. More...
uintb	getValue (uintb offset, int4 size) const
	Retrieve the value encoded in a (small) range of bytes. More...
void	setChunk (uintb offset, int4 size, const uint1 *val)
	Set values of an arbitrary sequence of bytes. More...
void	getChunk (uintb offset, int4 size, uint1 *res) const
	Retrieve an arbitrary sequence of bytes. More...

Protected Member Functions
virtual void	insert (uintb addr, uintb val)
	Overridden aligned word insert. More...
virtual uintb	find (uintb addr) const
	Overridden aligned word find. More...
virtual void	getPage (uintb addr, uint1 *res, int4 skip, int4 size) const
	Overridden getPage. More...
virtual void	setPage (uintb addr, const uint1 *val, int4 skip, int4 size)
	Overridden setPage. More...

Private Attributes
MemoryBank *	underlie
	Underlying memory object.
map< uintb, uint1 * >	page
	Overlayed pages.

Additional Inherited Members
Static Public Member Functions inherited from MemoryBank
static uintb	constructValue (const uint1 *ptr, int4 size, bool bigendian)
	Decode bytes to value. More...
static void	deconstructValue (uint1 *ptr, uintb val, int4 size, bool bigendian)
	Encode value to bytes. More...

Detailed Description

Memory bank that overlays some other memory bank, using a "copy on write" behavior.

Pages are copied from the underlying object only when there is a write. The underlying access routines are overridden to make optimal use of this page implementation. The underlying memory bank can be a null pointer in which case, this memory bank behaves as if it were initially filled with zeros.

Constructor & Destructor Documentation

MemoryPageOverlay()

MemoryPageOverlay::MemoryPageOverlay	(	AddrSpace *	spc,
		int4	ws,
		int4	ps,
		MemoryBank *	ul
	)

Constructor for page overlay.

A page overlay memory bank needs all the parameters for a generic memory bank and it needs to know the underlying memory bank being overlayed.

Parameters

spc	is the address space associated with the memory bank
ws	is the number of bytes in the preferred wordsize (must be power of 2)
ps	is the number of bytes in a page (must be power of 2)
ul	is the underlying MemoryBank

References underlie.

Member Function Documentation

find()

uintb MemoryPageOverlay::find ( uintb  addr ) const

protectedvirtual

Overridden aligned word find.

This derived method first looks for the aligned word in the mapped pages. If the address is not mapped, the search is forwarded to the underlying memory bank. If there is no underlying bank, zero is returned.

Parameters

addr	is the aligned offset of the word

Returns

the retrieved value

Implements MemoryBank.

References MemoryBank::constructValue(), MemoryBank::find(), MemoryBank::getPageSize(), MemoryBank::getSpace(), MemoryBank::getWordSize(), page, and underlie.

getPage()

void MemoryPageOverlay::getPage ( uintb  addr, uint1 *  res, int4  skip, int4  size  ) const

protectedvirtual

Overridden getPage.

The desired page is looked for in the page cache. If it doesn't exist, the request is forwarded to underlying bank. If there is no underlying bank, the result buffer is filled with zeros.

Parameters

addr	is the aligned offset of the page
res	is the pointer to where retrieved bytes should be stored
skip	is the offset into the page from where bytes should be retrieved
size	is the number of bytes to retrieve

Reimplemented from MemoryBank.

References MemoryBank::getPage(), page, and underlie.

insert()

void MemoryPageOverlay::insert ( uintb  addr, uintb  val  )

protectedvirtual

Overridden aligned word insert.

This derived method looks for a previously cached page of the underlying memory bank. If the cached page does not exist, it creates it and fills in its initial value by retrieving the page from the underlying bank. The new value is then written into cached page.

Parameters

addr	is the aligned address of the word to be written
val	is the value to be written at that word

Implements MemoryBank.

References MemoryBank::getPage(), MemoryBank::getPageSize(), page, and underlie.

setPage()

void MemoryPageOverlay::setPage ( uintb  addr, const uint1 *  val, int4  skip, int4  size  )

protectedvirtual

Overridden setPage.

First, a cached version of the desired page is searched for via its address. If it doesn't exist, it is created, and its initial value is filled via the underlying bank. The bytes to be written are then copied into the cached page.

Parameters

addr	is the aligned offset of the page to write
val	is a pointer to bytes to be written into the page
skip	is the offset into the page where bytes should be written
size	is the number of bytes to write

Reimplemented from MemoryBank.

References MemoryBank::getPage(), MemoryBank::getPageSize(), page, and underlie.

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The documentation for this class was generated from the following files:

• memstate.hh
• memstate.cc