From bf4d07d5394c370b5d52e99e5adf0e53fa342928 Mon Sep 17 00:00:00 2001
From: Jan Beulich <jbeulich@suse.com>
Date: Fri, 21 Apr 2023 12:08:15 +0200
Subject: [PATCH] x86: change fetch error handling in ckprefix()

Use a tristate (enum) return value type to be able to express all three
cases which are of interest to the (sole) caller. This also allows doing
away with the abuse of "rex_used".
---
 opcodes/i386-dis.c | 32 ++++++++++++++++++++------------
 1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/opcodes/i386-dis.c b/opcodes/i386-dis.c
index 393522f37ac..60bfa41a5ad 100644
--- a/opcodes/i386-dis.c
+++ b/opcodes/i386-dis.c
@@ -8953,7 +8953,11 @@ static const struct dis386 rm_table[][8] = {
 #define BND_PREFIX	0x04
 #define NOTRACK_PREFIX	0x05
 
-static int
+static enum {
+  ckp_okay,
+  ckp_bogus,
+  ckp_fetch_error,
+}
 ckprefix (instr_info *ins)
 {
   int newrex, i, length;
@@ -8963,7 +8967,8 @@ ckprefix (instr_info *ins)
   /* The maximum instruction length is 15bytes.  */
   while (length < MAX_CODE_LENGTH - 1)
     {
-      FETCH_DATA (ins->info, ins->codep + 1);
+      if (!fetch_code (ins->info, ins->codep + 1))
+	return ckp_fetch_error;
       newrex = 0;
       switch (*ins->codep)
 	{
@@ -8987,7 +8992,7 @@ ckprefix (instr_info *ins)
 	  if (ins->address_mode == mode_64bit)
 	    newrex = *ins->codep;
 	  else
-	    return 1;
+	    return ckp_okay;
 	  ins->last_rex_prefix = i;
 	  break;
 	case 0xf3:
@@ -9055,27 +9060,23 @@ ckprefix (instr_info *ins)
 	      ins->codep++;
 	      /* This ensures that the previous REX prefixes are noticed
 		 as unused prefixes, as in the return case below.  */
-	      ins->rex_used = ins->rex;
-	      return 1;
+	      return ins->rex ? ckp_bogus : ckp_okay;
 	    }
 	  ins->prefixes = PREFIX_FWAIT;
 	  break;
 	default:
-	  return 1;
+	  return ckp_okay;
 	}
       /* Rex is ignored when followed by another prefix.  */
       if (ins->rex)
-	{
-	  ins->rex_used = ins->rex;
-	  return 1;
-	}
+	return ckp_bogus;
       if (*ins->codep != FWAIT_OPCODE)
 	ins->all_prefixes[i++] = *ins->codep;
       ins->rex = newrex;
       ins->codep++;
       length++;
     }
-  return 0;
+  return ckp_bogus;
 }
 
 /* Return the name of the prefix byte PREF, or NULL if PREF is not a
@@ -9918,8 +9919,12 @@ print_insn (bfd_vma pc, disassemble_info *info, int intel_syntax)
 
   sizeflag = priv.orig_sizeflag;
 
-  if (!ckprefix (&ins) || ins.rex_used)
+  switch (ckprefix (&ins))
     {
+    case ckp_okay:
+      break;
+
+    case ckp_bogus:
       /* Too many prefixes or unused REX prefixes.  */
       for (i = 0;
 	   i < (int) ARRAY_SIZE (ins.all_prefixes) && ins.all_prefixes[i];
@@ -9928,6 +9933,9 @@ print_insn (bfd_vma pc, disassemble_info *info, int intel_syntax)
 			 (i == 0 ? "" : " "),
 			 prefix_name (&ins, ins.all_prefixes[i], sizeflag));
       return i;
+
+    case ckp_fetch_error:
+      return fetch_error (&ins);
     }
 
   ins.insn_codep = ins.codep;
-- 
2.30.2