scan_nextid

scan_nextid.rb

@@ -0,0 +1,73 @@
+require 'metasm'
+
+# metasm script to find all 'job_next_id' 'building_next_id' etc globals in dwarf fortress
+# tested in 34.07, linux/windows
+
+# code has pattern:
+#tryagain:
+#  cmp eax, [job_next_id]
+#  jl foobar
+#  ...
+#  mov eax, a_load_game_invalid_job_id_number
+#  ...
+#  jz tryagain
+#
+#a_load_game_invalid_job_id_number db "Load Game: Invalid Job ID Number, ", 0
+
+# disable decoding of relocs, takes a while for win binary ASLR aware
+ENV['METASM_NODECODE_RELOCS'] = '1'
+
+puts 'read file' if $VERBOSE
+binpath = ARGV.shift || 'Dwarf Fortress.exe'	# works with linux too
+dasm = Metasm::AutoExe.decode_file(binpath).disassembler
+
+puts 'scan "invalid id" strings' if $VERBOSE
+strings = {}
+dasm.pattern_scan(/Load Game: Invalid (\w|\s)* ID Number/) { |addr|
+	strings[addr] = dasm.decode_strz(addr)
+}
+
+xml = []
+puts 'dasm xrefs' if $VERBOSE
+strings.each { |addr, str|
+	xo = nil
+	dasm.pattern_scan([addr].pack('L')) { |xaddr| xo = xaddr }
+	if !xo
+		puts "no xref for #{str.inspect}"
+		next
+	end
+
+	# found the xref: disassemble next instruction, will loop back where we need
+	dasm.disassemble_fast(xo+4)
+
+	# find the previous 'jl'
+	a = xo
+	id_addr = nil
+	10.times {
+		di = dasm.di_including(a)
+		if di.opcode.name == 'jl'
+			# find previous 'cmp'
+			10.times {
+				di = dasm.di_including(a)
+				if di.opcode.name == 'cmp' and mrm = di.instruction.args.grep(Metasm::Ia32::ModRM)[0]
+					id_addr = dasm.normalize mrm.imm
+					break
+				end
+				a = di.address-1
+			}
+			break
+		end
+		a = di.address-1
+	}
+
+	if !id_addr
+		puts "no pattern for #{str.inspect}"
+		next
+	end
+
+	name = str[/Invalid (.*) ID Number/, 1].downcase.gsub(' ', '_') + '_next_id'
+
+	xml << "<global-address name='#{name}' value='0x#{'%08x' % id_addr}'/>"
+}
+
+puts xml.sort