set rip on linux

lib/asmrepl/linux.rb

@@ -44,6 +44,7 @@ def self.jitbuffer size
 
     # x86_64-linux-gnu/sys/ptrace.h
     PTRACE_GETREGS = 12
+    PTRACE_SETREGS = 13
 
     def self.traceme
       raise unless ptrace(PTRACE_TRACEME, 0, 0, 0).zero?
@@ -86,6 +87,10 @@ class ThreadState
         define_method(field) do
           to_ptr[Fiddle::SIZEOF_INT64_T * i, Fiddle::SIZEOF_INT64_T].unpack1("l!")
         end
+
+        define_method("#{field}=") do |v|
+          to_ptr[Fiddle::SIZEOF_INT64_T * i, Fiddle::SIZEOF_INT64_T] = [v].pack("l!")
+        end
       end
 
       define_singleton_method(:sizeof) do
@@ -98,6 +103,12 @@ def [] name
         to_ptr[Fiddle::SIZEOF_INT64_T * idx, Fiddle::SIZEOF_INT64_T].unpack1("l!")
       end
 
+      def []= name, val
+        idx = fields.index(name)
+        return unless idx
+        to_ptr[Fiddle::SIZEOF_INT64_T * idx, Fiddle::SIZEOF_INT64_T] = [val].pack("l!")
+      end
+
       def self.malloc
         new Fiddle::Pointer.malloc sizeof
       end
@@ -176,6 +187,12 @@ def state
         state
       end
 
+      def state= state
+        raise unless Linux.ptrace(PTRACE_SETREGS, @pid, 0, state).zero?
+
+        state
+      end
+
       def continue
         unless Linux.ptrace(Linux::PTRACE_CONT, @pid, 1, 0).zero?
           raise