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

#include <emulateutil.hh>

Inheritance diagram for ghidra::EmulateSnippet:

Public Member Functions
	EmulateSnippet (Architecture *g)
	Constructor.

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.

Architecture *	getArch (void) const
	Get the underlying Architecture.

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 ghidra::Emulate
	Emulate (void)
	generic emulator constructor

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...

Private Member Functions
uintb	getLoadImageValue (AddrSpace *spc, uintb offset, int4 sz) const
	Pull a value from the load-image given a specific address. More...

virtual void	executeUnary (void)
	Execute a unary arithmetic/logical operation.

virtual void	executeBinary (void)
	Execute a binary arithmetic/logical operation.

virtual void	executeLoad (void)
	Standard behavior for a p-code LOAD.

virtual void	executeStore (void)
	Standard behavior for a p-code STORE.

virtual void	executeBranch (void)
	Standard behavior for a BRANCH. More...

virtual bool	executeCbranch (void)
	Check if the conditional of a CBRANCH is true. More...

virtual void	executeBranchind (void)
	Standard behavior for a BRANCHIND.

virtual void	executeCall (void)
	Standard behavior for a p-code CALL.

virtual void	executeCallind (void)
	Standard behavior for a CALLIND.

virtual void	executeCallother (void)
	Standard behavior for a user-defined p-code op.

virtual void	executeMultiequal (void)
	Standard behavior for a MULTIEQUAL (phi-node)

virtual void	executeIndirect (void)
	Standard behavior for an INDIRECT op.

virtual void	executeSegmentOp (void)
	Behavior for a SEGMENTOP.

virtual void	executeCpoolRef (void)
	Standard behavior for a CPOOLREF (constant pool reference) op.

virtual void	executeNew (void)
	Standard behavior for (low-level) NEW op.

virtual void	fallthruOp (void)
	Standard p-code fall-thru semantics.

Private Attributes
Architecture *	glb
	The underlying Architecture for the program being emulated.

vector< PcodeOpRaw * >	opList
	Sequence of p-code ops to be executed.

vector< VarnodeData * >	varList
	Varnodes allocated for ops.

map< uintb, uintb >	tempValues
	Values stored in temporary registers.

PcodeOpRaw *	currentOp
	Current p-code op being executed.

int4	pos
	Index of current p-code op being executed.

Additional Inherited Members
Protected Attributes inherited from ghidra::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 * ghidra::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

Referenced by ghidra::ExecutablePcode::build().

◆ checkForLegalCode()

bool ghidra::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

References ghidra::CPUI_BRANCH, ghidra::CPUI_BRANCHIND, ghidra::CPUI_CALL, ghidra::CPUI_CALLIND, ghidra::CPUI_CALLOTHER, ghidra::CPUI_CPOOLREF, ghidra::CPUI_INDIRECT, ghidra::CPUI_MULTIEQUAL, ghidra::CPUI_NEW, ghidra::CPUI_SEGMENTOP, ghidra::CPUI_STORE, ghidra::PcodeOpRaw::getInput(), ghidra::PcodeOpRaw::getOpcode(), ghidra::PcodeOpRaw::getOutput(), ghidra::AddrSpace::getType(), ghidra::IPTR_CONSTANT, ghidra::IPTR_INTERNAL, ghidra::IPTR_PROCESSOR, ghidra::PcodeOpRaw::numInput(), and ghidra::VarnodeData::space.

Referenced by ghidra::ExecutablePcode::build().

◆ executeBranch()

void ghidra::EmulateSnippet::executeBranch ( void )

privatevirtual

Standard behavior for a BRANCH.

This routine performs a standard p-code BRANCH operation on the memory state. This same routine is used for CBRANCH operations if the condition has evaluated to true.

Implements ghidra::Emulate.

References ghidra::EmulatePcodeOp::currentOp, ghidra::Emulate::emu_halted, ghidra::AddrSpace::getType(), ghidra::IPTR_CONSTANT, ghidra::VarnodeData::offset, ghidra::EmulatePcodeOp::setCurrentOp(), and ghidra::VarnodeData::space.

◆ executeCbranch()

bool ghidra::EmulateSnippet::executeCbranch ( void )

privatevirtual

Check if the conditional of a CBRANCH is true.

This routine only checks if the condition for a p-code CBRANCH is true. It does not perform the actual branch.

Returns: the boolean state indicated by the condition

Implements ghidra::Emulate.

References ghidra::EmulatePcodeOp::currentOp, and ghidra::EmulatePcodeOp::getVarnodeValue().

◆ getLoadImageValue()

uintb ghidra::EmulateSnippet::getLoadImageValue	(	AddrSpace *	spc,
		uintb	offset,
		int4	sz
	)		const

private

Pull a value from the load-image given a specific address.

A contiguous chunk of memory is pulled from the load-image and returned as a constant value, respecting the endianess of the address space.

Parameters

spc	is the address space to pull the value from
offset	is the starting address offset (from within the space) to pull the value from
sz	is the number of bytes to pull from memory

Returns: indicated bytes arranged as a constant value

References ghidra::calc_mask(), ghidra::EmulatePcodeOp::glb, ghidra::AddrSpace::isBigEndian(), ghidra::Architecture::loader, and ghidra::LoadImage::loadFill().

◆ getTempValue()

uintb ghidra::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

Referenced by ghidra::ExecutablePcode::evaluate().

◆ getVarnodeValue()

uintb ghidra::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

References ghidra::EmulatePcodeOp::getLoadImageValue(), ghidra::AddrSpace::getType(), ghidra::IPTR_CONSTANT, ghidra::IPTR_INTERNAL, ghidra::VarnodeData::offset, ghidra::VarnodeData::size, and ghidra::VarnodeData::space.

◆ resetMemory()

void ghidra::EmulateSnippet::resetMemory ( void )

inline

Reset the emulation snippet.

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

References ghidra::Emulate::emu_halted, and ghidra::EmulatePcodeOp::setCurrentOp().

Referenced by ghidra::ExecutablePcode::evaluate().

◆ setCurrentOp()

void ghidra::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

References ghidra::Emulate::currentBehave, and ghidra::PcodeOpRaw::getBehavior().

◆ setVarnodeValue()

void ghidra::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

References ghidra::EmulatePcodeOp::getVarnodeValue().

Referenced by ghidra::ExecutablePcode::evaluate().

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

emulateutil.hh
emulateutil.cc

Public Member Functions

Private Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Member Function Documentation

◆ buildEmitter()

◆ checkForLegalCode()

◆ executeBranch()

◆ executeCbranch()

◆ getLoadImageValue()

◆ getTempValue()

◆ getVarnodeValue()

◆ resetMemory()

◆ setCurrentOp()

◆ setVarnodeValue()