#    This file is part of Metasm, the Ruby assembly manipulation suite
#    Copyright (C) 2006-2009 Yoann GUILLOT
#
#    Licence is LGPL, see LICENCE in the top-level directory

require 'metasm/cpu/arm/opcodes'
require 'metasm/decode'

module Metasm
class ARM
	# create the bin_mask for a given opcode
	def build_opcode_bin_mask(op)
		# bit = 0 if can be mutated by an field value, 1 if fixed by opcode
		op.bin_mask = 0
		op.fields.each { |k, (m, s)|
			op.bin_mask |= m << s
		}
		op.bin_mask = 0xffffffff ^ op.bin_mask
	end

	# create the lookaside hash from the first byte of the opcode
	def build_bin_lookaside
		lookaside = Array.new(256) { [] }

		opcode_list.each { |op|
			build_opcode_bin_mask op

			b   = (op.bin >> 20) & 0xff
			msk = (op.bin_mask >> 20) & 0xff
			b &= msk

			for i in b..(b | (255^msk))
				lookaside[i] << op if i & msk == b
			end
		}

		lookaside
	end

	def decode_findopcode(edata)
		return if edata.ptr+4 > edata.length
		di = DecodedInstruction.new(self)
		val = edata.decode_imm(:u32, @endianness)
		di.misc = val
		di if di.opcode = @bin_lookaside[(val >> 20) & 0xff].find { |op|
			(not op.props[:cond] or
			 ((val >> @fields_shift[:cond]) & @fields_mask[:cond]) != 0xf) and
			(op.bin & op.bin_mask) == (val & op.bin_mask)
		}
	end

	def disassembler_default_func
		df = DecodedFunction.new
		df
	end

	def decode_instr_op(edata, di)
		op = di.opcode
		di.instruction.opname = op.name
		val = di.misc	# saved decoded u32

		field_val = lambda { |f|
			r = (val >> @fields_shift[f]) & @fields_mask[f]
			case f
			when :i12; Expression.make_signed(r, 12)
			when :i24; Expression.make_signed(r, 24)
			when :i8_12; ((r >> 4) & 0xf0) | (r & 0xf)
			when :stype; [:lsl, :lsr, :asr, :ror][r]
			when :u; [:-, :+][r]
			else r
			end
		}

		if op.props[:cond]
			cd = %w[eq ne cs cc mi pl vs vc hi ls ge lt gt le al][field_val[:cond]]
			if cd != 'al'
				di.opcode = di.opcode.dup
				di.instruction.opname = di.opcode.name.dup
				di.instruction.opname[(op.props[:cond_name_off] || di.opcode.name.length), 0] = cd
				if di.opcode.props[:stopexec]
					di.opcode.props = di.opcode.props.dup
					di.opcode.props.delete :stopexec
				end
			end
		end

		op.args.each { |a|
			di.instruction.args << case a
			when :rd, :rn, :rm; Reg.new field_val[a]
			when :rm_rs; Reg.new field_val[:rm], field_val[:stype], Reg.new(field_val[:rs])
			when :rm_is; Reg.new field_val[:rm], field_val[:stype], field_val[:shifti]
			when :i12; Expression[field_val[a]]
			when :i24; Expression[field_val[a] << 2]
			when :i8_r
				i = field_val[:i8]
				r = field_val[:rotate]*2
				Expression[((i >> r) | (i << (32-r))) & 0xffff_ffff]
			when :mem_rn_rm, :mem_rn_i8_12, :mem_rn_rms, :mem_rn_i12
				b = Reg.new(field_val[:rn])
				o = case a
				when :mem_rn_rm; Reg.new(field_val[:rm])
				when :mem_rn_i8_12; field_val[:i8_12]
				when :mem_rn_rms; Reg.new(field_val[:rm], field_val[:stype], field_val[:shifti])
				when :mem_rn_i12; field_val[:i12]
				end
				Memref.new(b, o, field_val[:u], op.props[:baseincr])
			when :reglist
				di.instruction.args.last.updated = true if op.props[:baseincr]
				msk = field_val[a]
				l = RegList.new((0..15).map { |n| Reg.new(n) if (msk & (1 << n)) > 0 }.compact)
				l.usermoderegs = true if op.props[:usermoderegs]
				l
			else raise SyntaxError, "Internal error: invalid argument #{a} in #{op.name}"
			end
		}

		di.bin_length = 4
		di
	end

	def decode_instr_interpret(di, addr)
		if di.opcode.args[-1] == :i24
			di.instruction.args[-1] = Expression[di.instruction.args[-1] + addr + 8]
		end
		di
	end

	def init_backtrace_binding
		@backtrace_binding ||= {}
	end

	def get_backtrace_binding(di)
		a = di.instruction.args.map { |arg|
			case arg
			when Reg; arg.symbolic
			when Memref; arg.symbolic(di)
			else arg
			end
		}

		if binding = backtrace_binding[di.opcode.name]
			binding[di, *a]
		else
			puts "unhandled instruction to backtrace: #{di}" if $VERBOSE
			# assume nothing except the 1st arg is modified
			case a[0]
			when Indirection, Symbol; { a[0] => Expression::Unknown }
			when Expression; (x = a[0].externals.first) ? { x => Expression::Unknown } : {}
			else {}
			end.update(:incomplete_binding => Expression[1])
		end

	end

	def get_xrefs_x(dasm, di)
		if di.opcode.props[:setip]
			[di.instruction.args.last]
		else
			# TODO ldr pc, ..
			[]
		end
	end
end
end