fuzz update/node/lib/metasm/metasm/cpu/sh4/decode.rb
#    This file is part of Metasm, the Ruby assembly manipulation suite
#    Copyright (C) 2006-2010 Yoann GUILLOT
#
#    Licence is LGPL, see LICENCE in the top-level directory

require 'metasm/cpu/sh4/opcodes'
require 'metasm/decode'

module Metasm
class Sh4
	def build_opcode_bin_mask(op)
		op.bin_mask = 0
		op.args.each { |f|
			op.bin_mask |= @fields_mask[f] << @fields_shift[f]
		}
		op.bin_mask ^= 0xffff
	end

	def build_bin_lookaside
		lookaside = (0..0xf).inject({}) { |h, i| h.update i => [] }
		opcode_list.each { |op|
			build_opcode_bin_mask op
			lookaside[(op.bin >> 12) & 0xf] << op
		}
		lookaside
	end

	# depending on transfert size mode (sz flag), fmov instructions manipulate single ou double precision values
	# instruction aliasing appears when sz is not handled
	def transfer_size_mode(list)
		return list if list.find { |op| not op.name.include? 'mov' }
		@transfersz == 0 ? list.find_all { |op| op.name.include? 'fmov.s' } : list.reject { |op| op.name.include? 'fmov.s' }
	end

	# when pr flag is set, floating point instructions are executed as double-precision operations
	# thus register pair is used (DRn registers)
	def precision_mode(list)
		@fpprecision == 0 ? list.reject { |op| op.args.include? :drn } : list.find_all { |op| op.args.include? :frn }
	end

	def decode_findopcode(edata)
		di = DecodedInstruction.new(self)
		val = edata.decode_imm(:u16, @endianness)
		edata.ptr -= 2
		op = @bin_lookaside[(val >> 12) & 0xf].find_all { |opcode| (val & opcode.bin_mask) == opcode.bin }

		op = transfer_size_mode(op) if op.length == 2
		op = precision_mode(op) if op.length == 2

		if op.length > 1
			puts "current value: #{Expression[val]}, ambiguous matches:",
			op.map { |opcode| " #{opcode.name} - #{opcode.args.inspect} - #{Expression[opcode.bin]} - #{Expression[opcode.bin_mask]}" }
			#raise "Sh4 - Internal error"
		end

		if not op.empty?
			di.opcode = op.first
			di
		end
	end

	def decode_instr_op(edata, di)
		before_ptr = edata.ptr
		op = di.opcode
		di.instruction.opname = op.name
		di.opcode.props[:memsz] = (op.name =~ /\.l|mova/ ? 32 : (op.name =~ /\.w/ ? 16 : 8))
		val = edata.decode_imm(:u16, @endianness)

		field_val = lambda{ |f|
			r = (val >> @fields_shift[f]) & @fields_mask[f]
			case f
			when :@rm, :@rn ,:@_rm, :@_rn, :@rm_, :@rn_; GPR.new(r)
			when :@disppc
				# The effective address is formed by calculating PC+4,
				# clearing the lowest 2 bits, and adding the zero-extended 8-bit immediate i
				# multiplied by 4 (32-bit)/ 2 (16-bit) / 1 (8-bit).
				curaddr = di.address+4
				curaddr = (curaddr & 0xffff_fffc) if di.opcode.props[:memsz] == 32
				curaddr+r*(di.opcode.props[:memsz]/8)
			when :@disprm, :@dispr0rn; (r & 0xf) * (di.opcode.props[:memsz]/8)
			when :@disprmrn; (r & 0xf) * 4
			when :@dispgbr; Expression.make_signed(r, 16)
			when :disp8; di.address+4+2*Expression.make_signed(r, 8)
			when :disp12; di.address+4+2*Expression.make_signed(r, 12)
			when :s8; Expression.make_signed(r, 8)
			else r
			end
		}

		op.args.each { |a|
			di.instruction.args << case a
			when :r0; GPR.new 0
			when :rm, :rn; GPR.new field_val[a]
			when :rm_bank, :rn_bank; RBANK.new field_val[a]
			when :drm, :drn; DR.new field_val[a]
			when :frm, :frn; FR.new field_val[a]
			when :xdm, :xdn; XDR.new field_val[a]
			when :fvm, :fvn; FVR.new field_val[a]
			when :vbr; VBR.new
			when :gbr; GBR.new
			when :sr; SR.new
			when :ssr; SSR.new
			when :spc; SPC.new
			when :sgr; SGR.new
			when :dbr; DBR.new
			when :mach; MACH.new
			when :macl; MACL.new
			when :pr; PR.new
			when :fpul; FPUL.new
			when :fpscr; FPSCR.new
			when :pc; PC.new

			when :@rm, :@rn, :@disppc
				Memref.new(field_val[a], nil)
			when :@_rm, :@_rn
				Memref.new(field_val[a], nil, :pre)
			when :@rm_, :@rn_
				Memref.new(field_val[a], nil, :post)
			when :@r0rm
				Memref.new(GPR.new(0), GPR.new(field_val[:rm]))
			when :@r0rn, :@dispr0rn
				Memref.new(GPR.new(0), GPR.new(field_val[:rn]))
			when :@disprm
				Memref.new(field_val[a], GPR.new(field_val[:rm]))
			when :@disprmrn
				Memref.new(field_val[a], GPR.new(field_val[:rn]))

			when :disppc; Expression[field_val[:@disppc]]
			when :s8, :disp8, :disp12; Expression[field_val[a]]
			when :i16, :i8, :i5; Expression[field_val[a]]

			else raise SyntaxError, "Internal error: invalid argument #{a} in #{op.name}"
			end
		}

		di.bin_length += edata.ptr - before_ptr

		return if edata.ptr > edata.length

		di
	end

	def disassembler_default_func
		df = DecodedFunction.new
		df.backtrace_binding = {}
		(0..7 ).each { |i| r = "r#{i}".to_sym ; df.backtrace_binding[r] = Expression::Unknown }
		(8..15).each { |i| r = "r#{i}".to_sym ; df.backtrace_binding[r] = Expression[r] }
		df.backtracked_for = [BacktraceTrace.new(Expression[:pr], :default, Expression[:pr], :x)]
		df.btfor_callback = lambda { |dasm, btfor, funcaddr, calladdr|
			if funcaddr != :default
				btfor
			elsif di = dasm.decoded[calladdr] and di.opcode.props[:saveip]
				btfor
			else
				[]
			end
		}
		df
	end

	def backtrace_update_function_binding(dasm, faddr, f, retaddrlist, *wantregs)
		retaddrlist.map! { |retaddr| dasm.decoded[retaddr] ? dasm.decoded[retaddr].block.list.last.address : retaddr } if retaddrlist
		b = f.backtrace_binding

		bt_val = lambda { |r|
			next if not retaddrlist
			bt = []
			b[r] = Expression::Unknown	# break recursive dep
			retaddrlist.each { |retaddr|
				bt |= dasm.backtrace(Expression[r], retaddr,
					:include_start => true, :snapshot_addr => faddr, :origin => retaddr)
			}
			b[r] = ((bt.length == 1) ? bt.first : Expression::Unknown)
		}
		wantregs = GPR::Sym if wantregs.empty?
		wantregs.map { |r| r.to_sym }.each(&bt_val)
	end


	# interprets a condition code (in an opcode name) as an expression
	def decode_cmp_expr(di, a0, a1)
		case di.opcode.name
		when 'cmp/eq'; Expression[a0, :'==', a1]
		when 'cmp/ge'; Expression[a0, :'>=', a1] # signed
		when 'cmp/gt'; Expression[a0, :'>', a1] # signed
		when 'cmp/hi'; Expression[a0, :'>', a1] # unsigned
		when 'cmp/hs'; Expression[a0, :'>=', a1] # unsigned
		end
	end

	def decode_cmp_cst(di, a0)
		case di.opcode.name
		when 'cmp/pl'; Expression[a0, :'>', 0] # signed
		when 'cmp/pz'; Expression[a0, :'>=', 0] # signed
		end
	end

	def backtrace_binding
		@backtrace_binding ||= init_backtrace_binding
	end

	def opsz(di)
		ret = @size
		ret = 8 if di and di.opcode.name =~ /\.b/
		ret = 16 if di and di.opcode.name =~ /\.w/
		ret
	end

	def init_backtrace_binding
		@backtrace_binding ||= {}

		mask = lambda { |di| (1 << opsz(di)) - 1 }  # 32bits => 0xffff_ffff

		opcode_list.map { |ol| ol.name }.uniq.each { |op|
			@backtrace_binding[op] ||= case op
			when 'ldc', 'ldc.l', 'lds', 'lds.l', 'stc', 'stc.l', 'mov', 'mov.l', 'sts', 'sts.l'
				lambda { |di, a0, a1| { a1 => Expression[a0] }}
			when 'stc.w', 'stc.b', 'mov.w', 'mov.b'
				lambda { |di, a0, a1| { a1 => Expression[a0, :&, mask[di]] }}
			when 'movt'; lambda { |di, a0| { a0 => :t_bit }}
			when 'mova'; lambda { |di, a0, a1| { a1 => Expression[a0] }}
			when 'exts.b', 'exts.w', 'extu.w'
				lambda { |di, a0, a1| { a1 => Expression[a0, :&, mask[di]] }}
			when 'cmp/eq', 'cmp/ge', 'cmp/ge', 'cmp/gt', 'cmp/hi', 'cmp/hs'
				lambda { |di, a0, a1| { :t_bit => decode_cmp_expr(di, a0, a1) }}
			when 'cmp/pl', 'cmp/pz'
				lambda { |di, a0| { :t_bit => decode_cmp_cst(di, a0) }}
			when 'tst'; lambda { |di, a0, a1| { :t_bit => Expression[[a0, :&, mask[di]], :==, [a1, :&, mask[di]]] }}
			when 'rte'; lambda { |di| { :pc => :spc , :sr => :ssr }}
			when 'rts'; lambda { |di| { :pc => :pr }}
			when 'sets'; lambda { |di| { :s_bit => 1 }}
			when 'sett'; lambda { |di| { :t_bit => 1 }}
			when 'clrs'; lambda { |di| { :s_bit => 0 }}
			when 'clrt'; lambda { |di| { :t_bit => 0 }}
			when 'clrmac'; lambda { |di| { :macl => 0, :mach => 0 }}
			when 'jmp'; lambda { |di, a0| { :pc => a0 }}
			when 'jsr', 'bsr', 'bsrf'; lambda { |di, a0| { :pc => Expression[a0], :pr => Expression[di.address, :+, 2*2] }}
			when 'dt'; lambda { |di, a0|
				res = Expression[a0, :-, 1]
				{ :a0 => res, :t_bit => Expression[res, :==, 0] }
			}
			when 'add' ; lambda { |di, a0, a1| { a1 => Expression[[a0, :+, a1], :&, 0xffff_ffff] }}
			when 'addc' ; lambda { |di, a0, a1|
				res = Expression[[a0, :&, mask[di]], :+, [[a1, :&, mask[di]], :+, :t_bit]]
				{ a1 => Expression[a0, :+, [a1, :+, :t_bit]], :t_bit => Expression[res, :>, mask[di]] }
			}
			when 'addv' ; lambda { |di, a0, a1|
				res = Expression[[a0, :&, mask[di]], :+, [[a1, :&, mask[di]]]]
				{ a1 => Expression[a0, :+, [a1, :+, :t_bit]], :t_bit => Expression[res, :>, mask[di]] }
			}
			when 'shll16', 'shll8', 'shll2', 'shll' ; lambda { |di, a0|
				shift = { 'shll16' => 16, 'shll8' => 8, 'shll2' => 2, 'shll' => 1 }[op]
				{ a0 => Expression[[a0, :<<, shift], :&, 0xffff] }
			}
			when 'shlr16', 'shlr8', 'shlr2','shlr'; lambda { |di, a0|
				shift = { 'shlr16' => 16, 'shlr8' => 8, 'shlr2' => 2, 'shlr' => 1 }[op]
				{ a0 => Expression[a0, :>>, shift] }
			}
			when 'rotcl'; lambda { |di, a0| { a0 => Expression[[a0, :<<, 1], :|, :t_bit], :t_bit => Expression[a0, :>>, [opsz[di], :-, 1]] }}
			when 'rotcr'; lambda { |di, a0| { a0 => Expression[[a0, :>>, 1], :|, :t_bit], :t_bit => Expression[a0, :&, 1] }}
			when 'rotl'; lambda { |di, a0|
				shift_bit = [a0, :<<, [opsz[di], :-, 1]]
				{ a0 => Expression[[a0, :<<, 1], :|, shift_bit], :t_bit => shift_bit }
			}
			when 'rotr'; lambda { |di, a0|
				shift_bit = [a0, :>>, [opsz[di], :-, 1]]
				{ a0 => Expression[[a0, :>>, 1], :|, shift_bit], :t_bit => shift_bit }
			}
			when 'shal'; lambda { |di, a0|
				shift_bit = [a0, :<<, [opsz[di], :-, 1]]
				{ a0 => Expression[a0, :<<, 1], :t_bit => shift_bit }
			}
			when 'shar'; lambda { |di, a0|
				shift_bit = Expression[a0, :&, 1]
				{ a0 => Expression[a0, :>>, 1], :t_bit => shift_bit }
			}
			when 'sub';  lambda { |di, a0, a1| { a1 => Expression[[a1, :-, a0], :&, 0xffff_ffff] }}
			when 'subc'; lambda { |di, a0, a1| { a1 => Expression[a1, :-, [a0, :-, :t_bit]] }}
			when 'and', 'and.b'; lambda { |di, a0, a1| { a1 => Expression[[a0, :&, mask[di]], :|, [[a1, :&, mask[di]]]] }}
			when 'or', 'or.b';   lambda { |di, a0, a1| { a1 => Expression[[a0, :|, mask[di]], :|, [[a1, :&, mask[di]]]] }}
			when 'xor', 'xor.b'; lambda { |di, a0, a1| { a1 => Expression[[a0, :|, mask[di]], :^, [[a1, :&, mask[di]]]] }}
			when 'neg' ;  lambda { |di, a0, a1| { a1 => Expression[mask[di], :-, a0] }}
			when 'negc' ; lambda { |di, a0, a1| { a1 => Expression[[[mask[di], :-, a0], :-, :t_bit], :&, mask[di]] }}
			when 'not';   lambda { |di, a0, a1| { a1 => Expression[a0, :^, mask[di]] }}
			when 'nop'; lambda { |*a| {} }
			when /^b/; lambda { |*a| {} }	# branches
			end
		}

		@backtrace_binding
	end

	def get_backtrace_binding(di)
		a = di.instruction.args.map { |arg|
			case arg
			when GPR, XFR, XDR, FVR, DR, FR, XMTRX; arg.symbolic
			when MACH, MACL, PR, FPUL, PC, FPSCR; arg.symbolic
			when SR, SSR, SPC, GBR, VBR, SGR, DBR; arg.symbolic
			when Memref; arg.symbolic(di.address, di.opcode.props[:memsz]/8)
			else arg
			end
		}

		if binding = backtrace_binding[di.opcode.basename]
			bd = binding[di, *a] || {}
			di.instruction.args.grep(Memref).each { |m|
				next unless r = m.base and r.kind_of?(GPR)
				r = r.symbolic
				case m.action
				when :post
					bd[r] ||= Expression[r, :+, di.opcode.props[:memsz]/8]
				when :pre
					bd[r] ||= Expression[r, :-, di.opcode.props[:memsz]/8]
				end
			}
			bd
		else
			puts "unhandled instruction to backtrace: #{di}" if $VERBOSE
			{:incomplete_binding => Expression[1]}
		end
	end

	def get_xrefs_x(dasm, di)
		return [] if not di.opcode.props[:setip]

		val = case di.instruction.opname
		      when 'rts'; :pr
		      else di.instruction.args.last
		      end

		val = case val
		      when Reg; val.symbolic
		      when Memref; arg.symbolic(di.address, 4)
		      else val
		      end

		val = case di.instruction.opname
		      when 'braf', 'bsrf'; Expression[[di.address, :+, 4], :+, val]
		      else val
		      end

		[Expression[val]]
	end

	def backtrace_is_function_return(expr, di=nil)
		expr.reduce_rec == :pr
	end

	def delay_slot(di=nil)
		(di and di.opcode.props[:delay_slot]) ? 1 : 0
	end

	def replace_instr_arg_immediate(i, old, new)
		i.args.map! { |a|
			case a
			when Expression; a == old ? new : Expression[a.bind(old => new).reduce]
			when Memref
				a.base = (a.base == old ? new : Expression[a.base.bind(old => new).reduce]) if a.base.kind_of?(Expression)
				a
			else a
			end
		}
	end
end
end
