AliasChecker Class Reference

A light-weight class for analyzing pointers and aliasing on the stack. More...

#include <varmap.hh>

Classes
struct	AddBase
	A helper class holding a Varnode pointer reference and a possible index added to it. More...

Public Member Functions
void	gather (const Funcdata *f, AddrSpace *spc, bool defer)
	Gather Varnodes that point on the stack. More...
bool	hasLocalAlias (Varnode *vn) const
	Return true if it looks like the given Varnode is aliased by a pointer. More...
void	sortAlias (void) const
	Sort the alias starting offsets.

Static Public Member Functions
static void	gatherAdditiveBase (Varnode *startvn, vector< AddBase > &addbase)
	Gather result Varnodes for all sums that the given starting Varnode is involved in. More...
static uintb	gatherOffset (Varnode *vn)
	If the given Varnode is a sum result, return the constant portion of this sum. More...

Detailed Description

A light-weight class for analyzing pointers and aliasing on the stack.

The gather() method looks for pointer references into a specific AddressSpace (usually the stack). Then hasLocalAlias() checks if a specific Varnode within the AddressSpace is (possibly) aliased by one of the gathered pointer references.

Member Function Documentation

gather()

void AliasChecker::gather	(	const Funcdata *	f,
		AddrSpace *	spc,
		bool	defer
	)

Gather Varnodes that point on the stack.

For the given function and address space, gather all Varnodes that are pointers into the address space. The actual calculation can be deferred until the first time hasLocalAlias() is called.

Parameters

f	is the given function
spc	is the given address space
defer	is true is gathering is deferred

gatherAdditiveBase()

void AliasChecker::gatherAdditiveBase ( Varnode *  startvn, vector< AddBase > &  addbase  )

static

Gather result Varnodes for all sums that the given starting Varnode is involved in.

For every sum that involves startvn, collect the final result Varnode of the sum. A sum is any expression involving only the additive operators INT_ADD, INT_SUB, PTRADD, PTRSUB, and SEGMENTOP. The routine traverses forward recursively through all descendants of vn that are additive operations and collects all the roots of the traversed trees.

Parameters

startvn	is the Varnode to trace
addbase	will contain all the collected roots

gatherOffset()

uintb AliasChecker::gatherOffset ( Varnode *  vn )

static

If the given Varnode is a sum result, return the constant portion of this sum.

Treat vn as the result of a series of ADD operations. Examine all the constant terms of this sum and add them together by traversing the syntax tree rooted at vn, backwards, only through additive operations.

Parameters

vn	is the given Varnode to gather off of

Returns

the resulting sub-sum

hasLocalAlias()

bool AliasChecker::hasLocalAlias

(

Varnode *

vn

)

const

Return true if it looks like the given Varnode is aliased by a pointer.

This is gives a rough analysis of whether the given Varnode might be aliased by another pointer in the function. If false is returned, the Varnode is not likely to have an alias. If true is returned, the Varnode might have an alias.

Parameters

vn	is the given Varnode

Returns

true if the Varnode might have a pointer alias

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

• varmap.hh
• varmap.cc