x86, mpx: Decode MPX instruction to get bound violation information

Hello Dave Hansen,

The patch fcc7ffd67991: "x86, mpx: Decode MPX instruction to get bound violation information" from Nov 14, 2014, leads to the following static checker warning:

	arch/x86/mm/mpx.c:147 get_reg_offset()
	warn: masked condition is always false. '((insn->rex_prefix.value) & 2) = 1'

arch/x86/mm/mpx.c
138 switch (type) {
139 case REG_TYPE_RM:
140 regno = X86_MODRM_RM(insn->modrm.value);
141 if (X86_REX_B(insn->rex_prefix.value) = 1)
142 regno += 8;
143 break;
144
145 case REG_TYPE_INDEX:
146 regno = X86_SIB_INDEX(insn->sib.value);
147 if (X86_REX_X(insn->rex_prefix.value) = 1)

                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Was X86_REX_B() intended?

   148                          regno += 8;
   149                  break;
   150  
   151          case REG_TYPE_BASE:
   152                  regno = X86_SIB_BASE(insn->sib.value);
   153                  if (X86_REX_B(insn->rex_prefix.value) = 1)
   154                          regno += 8;
   155                  break;
   156  
   157          default:
   158                  pr_err("invalid register type");
   159                  BUG();
   160                  break;
   161          }

regards,
dan carpenter