Add documentation for the dynamic code modifications.

src/trusted/validator_ragel/unreviewed/validator_x86_32.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 10 matching lines @@
 
 %%{
   machine x86_32_validator;
   alphtype unsigned char;
   variable p current_position;
   variable pe end_of_bundle;
   variable eof end_of_bundle;
   variable cs current_state;
 
   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;
   }
 
   include decode_x86_32 "validator_x86_32_instruction.rl";
 
   special_instruction =
     (0x83 0xe0 0xe0 0xff (0xd0|0xe0)  | # naclcall/jmp %eax
      0x83 0xe1 0xe0 0xff (0xd1|0xe1)  | # naclcall/jmp %ecx
      0x83 0xe2 0xe0 0xff (0xd2|0xe2)  | # naclcall/jmp %edx
      0x83 0xe3 0xe0 0xff (0xd3|0xe3)  | # naclcall/jmp %ebx
@@ skipping 23 matching lines @@
     @{
       if (((current_position - data) & kBundleMask) != kBundleMask)
         instruction_info_collected |= BAD_CALL_ALIGNMENT;
     };
 
   main := ((call_alignment | one_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, 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;
        instruction_info_collected = 0;
      })*
     $err{
@@ skipping 61 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;
 }