Class: SeccompTools::Asm::Compiler

Inherits:

Object

• Object
• SeccompTools::Asm::Compiler

Defined in:

lib/seccomp-tools/asm/compiler.rb

Overview

Compile seccomp rules.

Constant Summary

JUMP_DISTANCE_MAX =

The farthest distance of a relative jump in BPF.

255

Instance Method Summary

• #compile! ⇒ Array<SeccompTools::BPF>

  Compiles the processed instructions.

• #initialize(source, filename, arch) ⇒ Compiler constructor

  Instantiate a Compiler object.

Constructor Details

#initialize(source, filename, arch) ⇒ Compiler

Instantiate a SeccompTools::Asm::Compiler object.

Parameters:

• source (String) —

  Input string.

• filename (String?) —

  Only used in error messages.

• arch (Symbol) —

  Architecture.

# File 'lib/seccomp-tools/asm/compiler.rb', line 26

def initialize(source, filename, arch)
  @scanner = Scanner.new(source, arch, filename:)
  @arch = arch
  @symbols = {}
end

Instance Method Details

#compile! ⇒ Array<SeccompTools::BPF>

Compiles the processed instructions.

Scans and parses the source, resolves the labels into relative jump distances, then emits one BPF per statement.

Returns:

• (Array<SeccompTools::BPF>) —

  Returns the compiled BPF array.

Raises:

• (SeccompTools::UnrecognizedTokenError) —

  If the source contains text that is not valid assembly.

• (SeccompTools::ParseError) —

  If the tokens do not form valid statements.

• (SeccompTools::DuplicateLabelError) —

  If a label is defined more than once.

• (SeccompTools::UndefinedLabelError) —

  If a jump refers to a label that is never defined.

• (SeccompTools::BackwardJumpError) —

  If a jump goes backward, which BPF cannot express.

# File 'lib/seccomp-tools/asm/compiler.rb', line 49

def compile!
  @scanner.validate!
  statements = SeccompAsmParser.new(@scanner).parse
  fixup_symbols(statements)
  resolve_symbols(statements)

  statements.map.with_index do |s, idx|
    @line = idx
    case s.type
    when :alu then emit_alu(*s.data)
    when :assign then emit_assign(*s.data)
    when :if then emit_cmp(*s.data)
    when :ret then emit_ret(*s.data)
    end
  end
end