Add documentation for the dynamic code modifications.

src/trusted/validator_ragel/unreviewed/validator_x86_64.rl

 /*
  * Copyright (c) 2012 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include <assert.h>
 #include <errno.h>
 #include <stddef.h>
 #include <stdio.h>
@@ skipping 11 matching lines @@
   variable pe end_of_bundle;
   variable eof end_of_bundle;
   variable cs current_state;
 
   action check_access {
     check_access(instruction_start - data, base, index, restricted_register, valid_targets,
                  &instruction_info_collected);
   }
 
   action rel8_operand {
-    instruction_info_collected |= RELATIVE_8BIT;
     rel8_operand(current_position + 1, data, jump_dests, size,
                  &instruction_info_collected);
   }
   action rel16_operand {
     #error rel16_operand should never be used in nacl
   }
   action rel32_operand {
-    instruction_info_collected |= RELATIVE_32BIT;
     rel32_operand(current_position + 1, data, jump_dests, size,
                   &instruction_info_collected);
   }
 
-  action opcode_in_imm {
+  action last_byte_is_not_immediate {
     instruction_info_collected |= LAST_BYTE_IS_NOT_IMMEDIATE;
   }
+
   action modifiable_instruction {
     instruction_info_collected |= MODIFIABLE_INSTRUCTION;
   }
 
   action process_0_operands {
     process_0_operands(&restricted_register, &instruction_info_collected);
   }
   action process_1_operand {
     process_1_operand(&restricted_register, &instruction_info_collected,
                       rex_prefix, operand_states);
@@ skipping 307 matching lines @@
       if (((current_position - data) & kBundleMask) != kBundleMask)
         instruction_info_collected |= BAD_CALL_ALIGNMENT;
     };
 
 
   main := ((call_alignment | normal_instruction | special_instruction)
      >{
        BitmapSetBit(valid_targets, current_position - data);
      }
      @{
-       if (instruction_info_collected & VALIDATION_ERRORS ||
-           options & CALL_USER_CALLBACK_ON_EACH_INSTRUCTION) {
+       if ((instruction_info_collected & VALIDATION_ERRORS_MASK) ||
+           (options & CALL_USER_CALLBACK_ON_EACH_INSTRUCTION)) {
          result &= user_callback(
              instruction_start, current_position,
              instruction_info_collected |
              ((restricted_register << RESTRICTED_REGISTER_SHIFT) &
               RESTRICTED_REGISTER_MASK), callback_data);
        }
        /* On successful match the instruction start must point to the next byte
         * to be able to report the new offset as the start of instruction
         * causing error.  */
        instruction_start = current_position + 1;
@@ skipping 88 matching lines @@
                                       user_callback, callback_data);
 
   /* We only use malloc for a large code sequences  */
   if (size > sizeof(bitmap_word)) {
     free(jump_dests);
     free(valid_targets);
   }
   if (!result) errno = EINVAL;
   return result;
 }