EmulateSnippet Class Reference

Emulate a snippet of PcodeOps out of a functional context. More...

#include <emulateutil.hh>

Inheritance diagram for EmulateSnippet:

Collaboration diagram for EmulateSnippet:

Public Member Functions
virtual	~EmulateSnippet (void)
	Destructor.
virtual void	setExecuteAddress (const Address &addr)
	Set the address of the next instruction to emulate.
virtual Address	getExecuteAddress (void) const
	Get the address of the current instruction being executed.
void	resetMemory (void)
	Reset the emulation snippet. More...
PcodeEmit *	buildEmitter (const vector< OpBehavior * > &inst, uintb uniqReserve)
	Provide the caller with an emitter for building the p-code snippet. More...
bool	checkForLegalCode (void) const
	Check for p-code that is deemed illegal for a snippet. More...
void	setCurrentOp (int4 i)
	Set the current executing p-code op by index. More...
void	setVarnodeValue (uintb offset, uintb val)
	Set a temporary register value in the machine state. More...
uintb	getVarnodeValue (VarnodeData *vn) const
	Retrieve the value of a Varnode from the current machine state. More...
uintb	getTempValue (uintb offset) const
	Retrieve a temporary register value directly. More...
Public Member Functions inherited from Emulate
void	setHalt (bool val)
	Set the halt state of the emulator. More...
bool	getHalt (void) const
	Get the halt state of the emulator. More...
void	executeCurrentOp (void)
	Do a single pcode op step. More...

Additional Inherited Members
Protected Attributes inherited from Emulate
bool	emu_halted
	Set to true if the emulator is halted.
OpBehavior *	currentBehave
	Behavior of the next op to execute.

Detailed Description

Emulate a snippet of PcodeOps out of a functional context.

Emulation is performed on a short sequence (snippet) of PcodeOpRaw objects. Control-flow emulation is limited to this snippet; BRANCH and CBRANCH operations can happen using p-code relative branching. Executing BRANCHIND, CALL, CALLIND, CALLOTHER, STORE, MULTIEQUAL, INDIRECT, SEGMENTOP, CPOOLOP, and NEW ops is treated as illegal and an exception is thrown. Expressions can only use temporary registers or read from the LoadImage.

The set of PcodeOpRaw objects in the snippet is provided by emitting p-code to the object returned by buildEmitter(). This is designed for one-time initialization of this class, which can be repeatedly used by calling resetMemory() between executions.

Member Function Documentation

buildEmitter()

PcodeEmit * EmulateSnippet::buildEmitter	(	const vector< OpBehavior * > &	inst,
		uintb	uniqReserve
	)

Provide the caller with an emitter for building the p-code snippet.

Any p-code produced by the PcodeEmit, when triggered by the caller, becomes part of the snippet that will get emulated by this. The caller should free the PcodeEmit object immediately after use.

Parameters

inst	is the opcode to behavior map the emitter will use
uniqReserve	is the starting offset within the unique address space for any temporary registers

Returns

the newly constructed emitter

checkForLegalCode()

bool EmulateSnippet::checkForLegalCode

(

void

)

const

Check for p-code that is deemed illegal for a snippet.

This method facilitates enforcement of the formal rules for snippet code.

• Branches must use p-code relative addressing.
• Snippets can only read/write from temporary registers
• Snippets cannot use BRANCHIND, CALL, CALLIND, CALLOTHER, STORE, SEGMENTOP, CPOOLREF, NEW, MULTIEQUAL, or INDIRECT

Returns

true if the current snippet is legal

getTempValue()

uintb EmulateSnippet::getTempValue

(

uintb

offset

)

const

Retrieve a temporary register value directly.

This allows the user to obtain the final value of the snippet calculation, without having to have the Varnode object in hand.

Parameters

offset

is the offset of the temporary register to retrieve

Returns

the calculated value or 0 if the register was never written

getVarnodeValue()

uintb EmulateSnippet::getVarnodeValue

(

VarnodeData *

vn

)

const

Retrieve the value of a Varnode from the current machine state.

If the Varnode is a temporary registers, the storage offset is used to look up the value from the machine state cache. If the Varnode represents a RAM location, the value is pulled directly out of the load-image. If the value does not exist, a "Read before write" exception is thrown.

Parameters

vn	is the Varnode to read

Returns

the retrieved value

resetMemory()

void EmulateSnippet::resetMemory ( void  )

inline

Reset the emulation snippet.

Reset the memory state, and set the first p-code op as current.

setCurrentOp()

void EmulateSnippet::setCurrentOp ( int4  i )

inline

Set the current executing p-code op by index.

The i-th p-code op in the snippet sequence is set as the currently executing op.

Parameters

i	is the index

setVarnodeValue()

void EmulateSnippet::setVarnodeValue ( uintb  offset, uintb  val  )

inline

Set a temporary register value in the machine state.

The temporary Varnode's storage offset is used as key into the machine state map.

Parameters

offset	is the temporary storage offset
val	is the value to put into the machine state

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

• emulateutil.hh
• emulateutil.cc