[PATCH] x86/Intel: don't accept bogus instructions

[Jan Beulich]

... due to their last byte looking like a suffix, when after its
stripping a matching instruction can be found. Since memory operand
size specifiers in Intel mode get converted into suffix representation
internally, we need to keep track of the actual mnemonic suffix which
may have got trimmed off, and check its validity while looking for a
matching template. I tripper over this quite some time again after
support for AMD's SSE5 instructions got removed, as at that point some
of the SSE5 mnemonics, other than expected, didn't fail to assemble.
But the problem affects many more instructions, namely (almost) all
MMX, SSE, and AVX ones as it looks. I don't think it makes sense to
add a testcase covering all of them, nor do I think it makes sense to
pick out some random examples for a new test case.

gas/
2016-06-30  Jan Beulich  <jbeulich@suse.com>

	* config/tc-i386.c (match_template): Add char parameter,
	consumed in Intel mode for an extra suffix check.
	(md_assemble): New local variable mnem_suffix.

--- 2016-06-30/gas/config/tc-i386.c
+++ 2016-06-30/gas/config/tc-i386.c
@@ -173,7 +173,7 @@ static void swap_operands (void);
 static void swap_2_operands (int, int);
 static void optimize_imm (void);
 static void optimize_disp (void);
-static const insn_template *match_template (void);
+static const insn_template *match_template (char);
 static int check_string (void);
 static int process_suffix (void);
 static int check_byte_reg (void);
@@ -3534,7 +3534,7 @@ void
 md_assemble (char *line)
 {
   unsigned int j;
-  char mnemonic[MAX_MNEM_SIZE];
+  char mnemonic[MAX_MNEM_SIZE], mnem_suffix;
   const insn_template *t;
 
   /* Initialize globals.  */
@@ -3552,6 +3552,7 @@ md_assemble (char *line)
   line = parse_insn (line, mnemonic);
   if (line == NULL)
     return;
+  mnem_suffix = i.suffix;
 
   line = parse_operands (line, mnemonic);
   this_operand = -1;
@@ -3595,7 +3596,7 @@ md_assemble (char *line)
      making sure the overlap of the given operands types is consistent
      with the template operand types.  */
 
-  if (!(t = match_template ()))
+  if (!(t = match_template (mnem_suffix)))
     return;
 
   if (sse_check != check_none
@@ -4719,14 +4720,14 @@ VEX_check_operands (const insn_template
 }
 
 static const insn_template *
-match_template (void)
+match_template (char mnem_suffix)
 {
   /* Points to template once we've found it.  */
   const insn_template *t;
   i386_operand_type overlap0, overlap1, overlap2, overlap3;
   i386_operand_type overlap4;
   unsigned int found_reverse_match;
-  i386_opcode_modifier suffix_check;
+  i386_opcode_modifier suffix_check, mnemsuf_check;
   i386_operand_type operand_types [MAX_OPERANDS];
   int addr_prefix_disp;
   unsigned int j;
@@ -4755,6 +4756,19 @@ match_template (void)
   else if (i.suffix == LONG_DOUBLE_MNEM_SUFFIX)
     suffix_check.no_ldsuf = 1;
 
+  memset (&mnemsuf_check, 0, sizeof (mnemsuf_check));
+  if (intel_syntax)
+    {
+      switch (mnem_suffix)
+	{
+	case BYTE_MNEM_SUFFIX:  mnemsuf_check.no_bsuf = 1; break;
+	case WORD_MNEM_SUFFIX:  mnemsuf_check.no_wsuf = 1; break;
+	case SHORT_MNEM_SUFFIX: mnemsuf_check.no_ssuf = 1; break;
+	case LONG_MNEM_SUFFIX:  mnemsuf_check.no_lsuf = 1; break;
+	case QWORD_MNEM_SUFFIX: mnemsuf_check.no_qsuf = 1; break;
+	}
+    }
+
   /* Must have right number of operands.  */
   i.error = number_of_operands_mismatch;
 
@@ -4800,6 +4814,14 @@ match_template (void)
 	      || (t->opcode_modifier.no_qsuf && suffix_check.no_qsuf)
 	      || (t->opcode_modifier.no_ldsuf && suffix_check.no_ldsuf)))
 	continue;
+      /* In Intel mode all mnemonic suffixes must be explicitly allowed.  */
+      if ((t->opcode_modifier.no_bsuf && mnemsuf_check.no_bsuf)
+	  || (t->opcode_modifier.no_wsuf && mnemsuf_check.no_wsuf)
+	  || (t->opcode_modifier.no_lsuf && mnemsuf_check.no_lsuf)
+	  || (t->opcode_modifier.no_ssuf && mnemsuf_check.no_ssuf)
+	  || (t->opcode_modifier.no_qsuf && mnemsuf_check.no_qsuf)
+	  || (t->opcode_modifier.no_ldsuf && mnemsuf_check.no_ldsuf))
+	continue;
 
       if (!operand_size_match (t))
 	continue;


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