#include <DwarfCfiAutomaton.h>

Collaboration diagram for DwarfCfiAutomaton:

Public Member Functions
	DwarfCfiAutomaton ()

	~DwarfCfiAutomaton ()

void	initialise (const DwarfState &startingState, uintptr_t nCodeLocation, size_t nCodeLen, int32_t nCodeAlignmentFactor, int32_t nDataAlignmentFactor, uintptr_t nStartingPc)

DwarfState *	execute (uintptr_t nCodeLocation, size_t nCodeLen, uintptr_t nBreakAt)

Private Member Functions
void	executeInstruction (uintptr_t &nLocation, uintptr_t &nPc)

Private Attributes
DwarfState	m_InitialState

DwarfState	m_CurrentState

int32_t	m_nCodeAlignmentFactor

int32_t	m_nDataAlignmentFactor

uintptr_t	m_nStartingPc

Detailed Description

The DWARF debugging standard uses a table for unwinding of the stack. This table has a column for each register and a row for each possible value of the program counter. Obviously, this table would be huge, so instead they encode it using instructions for an imaginary machine.

For each function, a new table is made and initialised. Opcodes cause sequential creation of the table. An extra column is added for the CFA (current frame address - how to find the current frame base) and (possibly) the return address.

Definition at line 73 of file DwarfCfiAutomaton.h.

Constructor & Destructor Documentation

DwarfCfiAutomaton::DwarfCfiAutomaton ( )

Constructor - Creates the initial starting state with all registers 'undefined'.

Definition at line 24 of file DwarfCfiAutomaton.cc.

DwarfCfiAutomaton::~DwarfCfiAutomaton ( )

Destructor - Doesn't do much, as we don't use dynamic memory.

Definition at line 30 of file DwarfCfiAutomaton.cc.

Member Function Documentation

DwarfState * DwarfCfiAutomaton::execute	(	uintptr_t	nCodeLocation,
		size_t	nCodeLen,
		uintptr_t	nBreakAt
	)

Executes code at the location given until the instruction pointer passes nCodeLocation+nCodeLen or the instruction pointer equals nBreakAt.

Parameters

nCodeLocation	Location of the CFA instruction stream to execute.
nCodeLen	Maximum length (in bytes) of code to execute.
nBreakAt	Execution should stop when the table row for this instruction has been constructed.

Returns: The ending state on success, zero on failure.

Definition at line 55 of file DwarfCfiAutomaton.cc.

References executeInstruction(), m_CurrentState, and m_nStartingPc.

Referenced by initialise(), and DwarfUnwinder::unwind().

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void DwarfCfiAutomaton::executeInstruction	(	uintptr_t &	nLocation,
		uintptr_t &	nPc
	)

private

Execute one instruction from the location given by nLocation, incrementing it to the next.

Definition at line 70 of file DwarfCfiAutomaton.cc.

References DwarfUnwinder::decodeSleb128(), DwarfUnwinder::decodeUleb128(), ERROR, Hex, DwarfState::m_CfaRegister, DwarfState::m_CfaState, m_CurrentState, m_nCodeAlignmentFactor, m_nDataAlignmentFactor, DwarfState::m_R, and DwarfState::m_RegisterStates.

Referenced by execute().

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void DwarfCfiAutomaton::initialise	(	const DwarfState &	startingState,
		uintptr_t	nCodeLocation,
		size_t	nCodeLen,
		int32_t	nCodeAlignmentFactor,
		int32_t	nDataAlignmentFactor,
		uintptr_t	nStartingPc
	)

Points the automaton to code which it should use to construct the machine starting state. This state is saved for use by a DW_CFA_restore instruction.

Parameters