/// <summary>
/// Generates a new basic block that starts at the supplied base address.
/// </summary>
/// <param name="p">The process interactor used to read data from the target.</param>
/// <param name="baseAddress">The base address of the basic block.</param>
/// <param name="blocks">
/// A set of basic blocks that relate to the current block through either direct or indirect connections.
/// </param>
/// <param name="maxDepth">
/// The maximum number of code flow indirections to be followed. If set to -1, no maximum indirection count is
/// enforced.
/// </param>
/// <returns>Returns a basic block that starts at the supplied address.</returns>
public static BasicBlock GenerateBlock(
PInteractor p,
IntPtr baseAddress,
out HashSet<BasicBlock> blocks,
long maxDepth = -1)
{
SysInteractor.Init();
blocks = new HashSet<BasicBlock>();
HashSet<Page> pages = new HashSet<Page>();
BasicBlock block = BasicBlock.GenerateBlock(p, baseAddress, ref blocks, ref pages, maxDepth);
BasicBlock.RemoveDuplicateInstructions(ref blocks);
return block;
}
/// <summary>
/// Generates a new basic block that starts at the supplied base address.
/// </summary>
/// <param name="p">The process interactor used to read data from the target.</param>
/// <param name="baseAddress">The base address of the basic block.</param>
/// <param name="blocks">
/// A set of basic blocks that relate to the current block through either direct or indirect connections.
/// </param>
/// <param name="pages">A set of pages that have been read while analyzing basic blocks.</param>
/// <param name="maxDepth">
/// The maximum number of code flow indirections to be followed. If set to -1, no maximum indirection count is
/// enforced.
/// </param>
/// <param name="currentDepth">The current number of indirections that have been followed.</param>
/// <returns>Returns a basic block that starts at the supplied address.</returns>
/// <remarks>
/// Unhandled ends to basic blocks (descriptions taken from wikipedia):
/// - Instructions which may throw an exception
/// - Function calls can be at the end of a basic block if they may not return, such as functions which throw
/// exceptions or special calls like C's longjmp and exit
/// Unhandled beginnings to basic blocks (descriptions taken from wikipedia):
/// - Instructions following ones that throw exceptions
/// - Exception handlers.
/// </remarks>
public static BasicBlock GenerateBlock(
PInteractor p,
IntPtr baseAddress,
ref HashSet<BasicBlock> blocks,
ref HashSet<Page> pages,
long maxDepth = -1,
long currentDepth = 0)
{
// Prepare the base block.
BasicBlock block = null;
// If a block at this address already exists, return that block.
foreach (BasicBlock b in blocks)
{
if (b.Instructions[0].Address == baseAddress)
{
return b;
}
}
// If the block did not exist, then create a new block.
if (block == null)
{
block = new BasicBlock();
blocks.Add(block);
}
// Get the address of the page where the block exists.
Page currentPage = null;
IntPtr pageBase = new IntPtr((baseAddress.ToInt64() / SysInteractor.PageSize) * SysInteractor.PageSize);
foreach (Page page in pages)
{
if (page.Address.Equals(pageBase))
{
currentPage = page;
break;
}
}
// Read the data from the page where the block exists.
if (currentPage == null)
{
currentPage = new Page();
currentPage.Address = pageBase;
currentPage.Data = new byte[SysInteractor.PageSize];
if (!p.Read(currentPage.Address, currentPage.Data))
{
Console.WriteLine("Unable to read address 0x" + currentPage.Address.ToInt32().ToString("x").PadLeft(8, '0'));
Console.WriteLine("Error: " + Marshal.GetLastWin32Error());
return new BasicBlock();
}
currentPage.Instructions =
BasicBlock.d.DisassembleInstructions(currentPage.Data, currentPage.Address).ToList();
if (currentPage.Instructions.Count == 0)
{
return new BasicBlock();
}
pages.Add(currentPage);
}
int i = 0;
for (; i < currentPage.Instructions.Count; ++i)
{
if (currentPage.Instructions[i].Address == baseAddress)
{
// Break once the instruction has been found.
break;
}
else if ((ulong)currentPage.Instructions[i].Address > (ulong)baseAddress)
{
Console.WriteLine("Disassembly failed for address: 0x" + currentPage.Instructions[i].Address.ToString("x").PadLeft(8, '0'));
return new BasicBlock();
}
}
if (i >= currentPage.Instructions.Count)
{
Console.WriteLine("Need to use scanner to identify and decompose regions, rather than single pages.");
return new BasicBlock();
}
// Verify that no control flow instructions are added in the middle of a basic block.
while (
// TODO: verify this still works after adjusting the call verification logic.
currentPage.Instructions[i].FlowType != Instruction.ControlFlow.Call &&
currentPage.Instructions[i].FlowType != Instruction.ControlFlow.ConditionalBranch &&
currentPage.Instructions[i].FlowType != Instruction.ControlFlow.Return &&
currentPage.Instructions[i].FlowType != Instruction.ControlFlow.UnconditionalBranch)
{
// Add the non-control-modifying instructions.
block.Instructions.Add(currentPage.Instructions[i++]);
if (i >= currentPage.Instructions.Count)
{
Console.WriteLine("Need to use scanner to identify and decompose regions, rather than single pages.");
return new BasicBlock();
}
}
// Add the control-modifying instruction.
block.Instructions.Add(currentPage.Instructions[i]);
// End parsing if this is the end of the block.
if (currentPage.Instructions[i].FlowType == Instruction.ControlFlow.Return)
{
return block;
}
// Parse the branch block.
BasicBlock branchBlock;
if (maxDepth == -1 || currentDepth <= maxDepth)
{
// TODO: verify this still works after adjusting the call verification logic.
// This handles CND_BRANCH, UNC_BRANCH, and CALL.
if (currentPage.Instructions[i].FlowType == Instruction.ControlFlow.Call)
{
branchBlock = blocks.FirstOrDefault(
x => x.Instructions.Count > 0 &&
x.Instructions[0].Address == currentPage.Instructions[i].BranchTarget);
if (branchBlock == null)
{
// Do not expand calls. Add a stub block, instead.
branchBlock = new BasicBlock();
// TODO: verify that creating an invalid instruction works.
branchBlock.Instructions.Add(
Instruction.CreateInvalidInstruction(currentPage.Instructions[i].BranchTarget));
blocks.Add(branchBlock);
}
}
else
{
branchBlock = GenerateBlock(
p, new IntPtr((long)currentPage.Instructions[i].BranchTarget), ref blocks, ref pages, maxDepth, currentDepth + 1);
}
block.Next.Add(branchBlock);
branchBlock.Previous.Add(block);
}
if (currentPage.Instructions[i].FlowType == Instruction.ControlFlow.ConditionalBranch ||
currentPage.Instructions[i].FlowType == Instruction.ControlFlow.Call)
{
BasicBlock nextBlock = GenerateBlock(
p, new IntPtr((long)currentPage.Instructions[++i].Address), ref blocks, ref pages, maxDepth, currentDepth);
block.Next.Add(nextBlock);
nextBlock.Previous.Add(block);
}
// Return results.
return block;
}
