Builder

Builder interface, nodes, and passes.

Overview

Both BaseBuilder and BaseCompiler interfaces describe emitters that emit into a representation that allows further processing. The code stored in such representation is completely safe to be patched, simplified, reordered, obfuscated, removed, injected, analyzed, or processed some other way. Each instruction, label, directive, or other building block is stored as BaseNode (or derived class like InstNode or LabelNode) and contains all the information necessary to pass that node later to the assembler.

BaseBuilder is an emitter that inherits from BaseEmitter interface. It was designed to provide a maximum compatibility with the existing BaseAssembler emitter so users can move from assembler to builder when needed, for example to implement post-processing, which is not possible with Assembler.

Builder Nodes

BaseBuilder doesn't generate machine code directly, it uses an intermediate representation based on nodes, however, it allows to serialize to BaseAssembler when the code is ready to be encoded.

There are multiple node types used by both BaseBuilder and BaseCompiler :

• Basic nodes:
  • BaseNode - Base class for all nodes.
  • InstNode - Represents an instruction node.
  • AlignNode - Represents an alignment directive (.align).
  • LabelNode - Represents a location where to bound a Label.
• Data nodes:
  • EmbedDataNode - Represents data.
  • EmbedLabelNode - Represents Label address embedded as data.
  • EmbedLabelDeltaNode - Represents a difference of two labels embedded in data.
  • ConstPoolNode - Represents a constant pool data embedded as data.
• Informative nodes:
  • CommentNode - Represents a comment string, doesn't affect code generation.
  • SentinelNode - A marker that can be used to remember certain position in code or data, doesn't affect code generation. Used by FuncNode to mark the end of a function.
• Other nodes are provided by Compiler infrastructure.

Builder Examples

• x86::Builder - Builder implementation targeting X86 and X86_64 architectures.
• a64::Builder - Builder implementation targeting AArch64 architecture.

Classes

class NodeList

class BaseBuilder

class BaseNode

struct BaseNode::AnyData

struct BaseNode::AlignData

struct BaseNode::InstData

struct BaseNode::EmbedData

struct BaseNode::SentinelData

class InstNode

class InstNodeWithOperands<kN>

class SectionNode

class LabelNode

class AlignNode

class EmbedDataNode

class EmbedLabelNode

class EmbedLabelDeltaNode

class ConstPoolNode

class CommentNode

class SentinelNode

class Pass

Enumerations

enum class NodeType : uint8_t

enum class NodeFlags : uint8_t

enum class SentinelType : uint8_t

Enumeration Type Documentation

class NodeType : uint8_tenumstrong

Type of node used by BaseBuilder and BaseCompiler.

Constant	Description
kNone	Invalid node (internal, don't use).
kInst	Node is InstNode.
kSection	Node is SectionNode.
kLabel	Node is LabelNode.
kAlign	Node is AlignNode.
kEmbedData	Node is EmbedDataNode.
kEmbedLabel	Node is EmbedLabelNode.
kEmbedLabelDelta	Node is EmbedLabelDeltaNode.
kConstPool	Node is ConstPoolNode.
kComment	Node is CommentNode.
kSentinel	Node is SentinelNode.
kJump	Node is JumpNode (acts as InstNode).
kFunc	Node is FuncNode (acts as LabelNode).
kFuncRet	Node is FuncRetNode (acts as InstNode).
kInvoke	Node is InvokeNode (acts as InstNode).
kUser	First id of a user-defined node.

class NodeFlags : uint8_tenumstrong

Node flags, specify what the node is and/or does.

Constant	Description
kNone	No flags.
kIsCode	Node is code that can be executed (instruction, label, align, etc...).
kIsData	Node is data that cannot be executed (data, const-pool, etc...).
kIsInformative	Node is informative, can be removed and ignored.
kIsRemovable	Node can be safely removed if unreachable.
kHasNoEffect	Node does nothing when executed (label, align, explicit nop).
kActsAsInst	Node is an instruction or acts as it.
kActsAsLabel	Node is a label or acts as it.
kIsActive	Node is active (part of the code).

class SentinelType : uint8_tenumstrong

Type of the sentinel (purely informative purpose).

Constant	Description
kUnknown	Type of the sentinel is not known.
kFuncEnd	This is a sentinel used at the end of FuncNode.