x86: never set i386_cpu_flags' "unused" field

Setting this field risks cpu_flags_all_zero() mistakenly returning
"false" when the object passed in was e.g. the result of ANDing together
two objects which had the bit set, or ANDNing together an object with
the field set and one with the field clear.

While there also avoid setting CpuNo64: Like Cpu64 this is driven
differently anyway and hence shouldn't be set anywhere by default.

Note that the moving of the two items in i386-gen.c's cpu_flags[] is
only for documentation purposes (and slight reducing of overhead), as
the fields are sorted anyway upon program start.

diff --git a/opcodes/i386-gen.c b/opcodes/i386-gen.c
index ae650d895975d0ebaf69205b1f9d27da64d6b932..d18a7d27545ccec1364ab19d9951627b01d4bec4 100644 (file)
--- a/opcodes/i386-gen.c
+++ b/opcodes/i386-gen.c
@@ -628,8 +628,6 @@ static bitfield cpu_flags[] =
   BITFIELD (CpuPREFETCHWT1),
   BITFIELD (CpuSE1),
   BITFIELD (CpuCLWB),
-  BITFIELD (Cpu64),
-  BITFIELD (CpuNo64),
   BITFIELD (CpuMPX),
   BITFIELD (CpuAVX512IFMA),
   BITFIELD (CpuAVX512VBMI),
@@ -676,6 +674,8 @@ static bitfield cpu_flags[] =
   BITFIELD (CpuINVLPGB),
   BITFIELD (CpuTLBSYNC),
   BITFIELD (CpuSNP),
+  BITFIELD (Cpu64),
+  BITFIELD (CpuNo64),
 #ifdef CpuUnused
   BITFIELD (CpuUnused),
 #endif
@@ -1068,9 +1068,10 @@ process_i386_cpu_flag (FILE *table, char *flag, int macro,
       else
        next = flag + 1;
 
-      /* First we turn on everything except for cpu64.  */
+      /* First we turn on everything except for cpu64, cpuno64, and - if
+         present - the padding field.  */
       for (i = 0; i < ARRAY_SIZE (flags); i++)
-       if (flags[i].position != Cpu64)
+       if (flags[i].position < Cpu64)
          flags[i].value = 1;
 
       /* Turn off selective bits.  */

diff --git a/opcodes/i386-init.h b/opcodes/i386-init.h
index 393fdcabe6fd829ad18809add7f3c7f9252fbd7f..df2f7bcd4985721b6c38a82c4f2a0985ce71248d 100644 (file)
--- a/opcodes/i386-init.h
+++ b/opcodes/i386-init.h
@@ -25,7 +25,7 @@
       1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
       1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
       1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
-      1, 1, 0, 1, 1 } }
+      1, 1, 0, 0, 0 } }
 
 #define CPU_GENERIC32_FLAGS \
   { { 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \

diff --git a/opcodes/i386-opc.h b/opcodes/i386-opc.h
index a7acaebe4bd7e2ec7642147feac65ad0117701c2..cba7cd2d36a26f2243e07696417f9581720bbe32 100644 (file)
--- a/opcodes/i386-opc.h
+++ b/opcodes/i386-opc.h
@@ -272,6 +272,9 @@ enum
   CpuTLBSYNC,
   /* SNP instructions required */
   CpuSNP,
+
+  /* NOTE: These last three items need to remain last and in this order. */
+
   /* 64bit support required  */
   Cpu64,
   /* Not supported in the 64bit mode  */
@@ -417,6 +420,7 @@ typedef union i386_cpu_flags
       unsigned int cpuinvlpgb:1;
       unsigned int cputlbsync:1;
       unsigned int cpusnp:1;
+      /* NOTE: These last three fields need to remain last and in this order. */
       unsigned int cpu64:1;
       unsigned int cpuno64:1;
 #ifdef CpuUnused