Class: Ragweed::Rasm::Instruction

Inherits:
Object
  • Object
show all
Defined in:
lib/ragweed/rasm/isa.rb

Overview

An X86 instruction. For the most part, you do two things with an instruction in Rasm: create it, and call to_s to get its raw value.

Direct Known Subclasses

Arith, Call, Cmp, IncDec, Int, Iret, Jcc, Jmp, Lea, Leave, Mov, Nop, Not, Pop, Popad, Popf, Push, Pushad, Pushf, Ret, Shift, Test

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(x = nil, y = nil) ⇒ Instruction

Never called directly (see subclasses below)



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# File 'lib/ragweed/rasm/isa.rb', line 265

def initialize(x=nil, y=nil)
  @buf = Ragweed::Sbuf.new
  self.src = y
  self.dst = x
  @loc = nil
end

Instance Attribute Details

#dst ⇒ Object

Returns the value of attribute dst.



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# File 'lib/ragweed/rasm/isa.rb', line 232

def dst
  @dst
end

#src ⇒ Object

Returns the value of attribute src.



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# File 'lib/ragweed/rasm/isa.rb', line 231

def src
  @src
end

Class Method Details

.i(*args) ⇒ Object 



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# File 'lib/ragweed/rasm/isa.rb', line 234

def self.i(*args); self.new *args; end

Instance Method Details

#add(v, immed = false, half = false) ⇒ Object

Add material to the instruction. Not user-servicable.



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# File 'lib/ragweed/rasm/isa.rb', line 358

def add(v, immed=false, half=false)
  return(nil) if not v

  if v.number?
    if (v < 0x100) and (v > -128) and not immed
      if v < 0
        @buf.stl8(v.sx8)
      else
        @buf.stl8(v)
      end
    else
      if not half
        @buf.stl32(v.sx32)
      else
        @buf.stl16(v.sx16)
      end
    end
  else
    @buf.straw v
  end
end

#coerce(v) ⇒ Object 



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# File 'lib/ragweed/rasm/isa.rb', line 248

def coerce(v)
  if v
    v = v.derive
    v = v.to_i if v.kind_of? Ragweed::Ptr
    if v.kind_of? Array
      v = v[0].clone
      v.indir = true
    end
    v = Immed.new(v) if v.number?
  end
  v
end

#dst_imm? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ragweed/rasm/isa.rb', line 242

def dst_imm?; @dst and @dst.kind_of? Immed; end

#dst_lab? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ragweed/rasm/isa.rb', line 246

def dst_lab?; @dst and @dst.kind_of? Label; end

#dst_reg? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ragweed/rasm/isa.rb', line 238

def dst_reg?; @dst and @dst.kind_of? Register; end

#locate(loc) ⇒ Object

What Subprogram#assemble uses to patch instruction locations. Not user-servicable



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# File 'lib/ragweed/rasm/isa.rb', line 277

def locate(loc); @loc = loc; end

#modrm(op1, op2) ⇒ Object

Calculate ModR/M bits for the instruction; this is the source/destination operand encoding.

Raises:



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# File 'lib/ragweed/rasm/isa.rb', line 293

def modrm(op1, op2)
  raise(BadArg, "two indirs") if op1.indir and op2.indir

  if op1.indir or op2.indir
    base = 0x80
    (op1.indir) ? (o, alt = [op1,op2]) : (o,alt = [op2,op1])
    if o.disp and (o.disp < 0x1000)
      base = 0x40
    end
    if (not o.disp) or (o.disp == 0)
      base = 0x0
    end
  end

  if op1.indir
    if op1.combined? or op1.scaled? or (op1.code == Register::EBP)
      sib(op1, op2, base)
    else
      return base + (op2.code << 3) + op1.code
    end
  elsif op2.indir
    if op2.combined? or op2.scaled? or (op2.code == Register::EBP)
      sib(op2, op1, base)
    else
      return base + (op1.code << 3) + op2.code
    end
  else
    return 0xc0 + (op2.code << 3) + op1.code
  end
end

#patch(patches) ⇒ Object

Not user-servicable



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# File 'lib/ragweed/rasm/isa.rb', line 279

def patch(patches)
  if @dst.kind_of? Label
    raise(BadArg, "need to have location first") if not @loc
    offset = patches[@dst.val] - @Loc
    @dst = Immed.new offset
    if offset < 0
      offset -= self.to_s
      @dst = Immed.new offset
    end
  end
end

#sib(indir, alt, base) ⇒ Object 



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# File 'lib/ragweed/rasm/isa.rb', line 324

def sib(indir, alt, base)
  modpart = (base+4) + (alt.code << 3)

  if indir.scaled?
    case indir.scale
    when 2
      sbase = 0x40
    when 4
      sbase = 0x80
    when 8
      sbase = 0xc0
    else
      raise BadArg, "scale must be 2, 4, or 8"
    end
  else
    sbase = 0
  end

  col = indir.reg1.code

  if indir.combined?
    row = indir.reg2.code
  else
    row = 4
  end

  # pp [col,row,sbase]

  sibpart = sbase + (row << 3) + (col)

  return (modpart.chr) + (sibpart.chr)
end

#src_imm? ⇒ Boolean

Are the source/dest operands immediates?

Returns:

  • (Boolean) 


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# File 'lib/ragweed/rasm/isa.rb', line 241

def src_imm?; @src and @src.kind_of? Immed; end

#src_lab? ⇒ Boolean

Are the source/dest operands labels?

Returns:

  • (Boolean) 


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# File 'lib/ragweed/rasm/isa.rb', line 245

def src_lab?; @src and @src.kind_of? Label; end

#src_reg? ⇒ Boolean

Are the source/dest operands registers?

Returns:

  • (Boolean) 


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# File 'lib/ragweed/rasm/isa.rb', line 237

def src_reg?; @src and @src.kind_of? Register; end

#to_s ⇒ Object

Never called directly (see subclasses).



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# File 'lib/ragweed/rasm/isa.rb', line 381

def to_s; ret = @buf.content; @buf.clear!; ret; end