xtensa: use property tables for correct disassembly

xtensa disassembler does not use information from the .xt.prop sections
to switch between code/data disassembly in text sections. This may
result in incorrect disassembly when data is interpreted as code and
disassembler loses synchronization with instruction stream. Use .xt.prop
section information to correctly interpret code and data and synchronize
with instruction stream.

2018-06-04  Max Filippov  <jcmvbkbc@gmail.com>
bfd/
	* elf32-xtensa.c (xtensa_read_table_entries): Make global.
	(compute_fill_extra_space): Drop declaration. Rename function to
	xtensa_compute_fill_extra_space.
	(compute_ebb_actions, remove_dead_literal): Update references to
	compute_fill_extra_space.

include/
	* elf/xtensa.h (xtensa_read_table_entries)
	(xtensa_compute_fill_extra_space): New declarations.

opcodes/
	* xtensa-dis.c (bfd.h, elf/xtensa.h): New includes.
	(dis_private): Add new fields for property section tracking.
	(xtensa_coalesce_insn_tables, xtensa_find_table_entry)
	(xtensa_instruction_fits): New functions.
	(fetch_data): Bump minimal fetch size to 4.
	(print_insn_xtensa): Make struct dis_private static.
	Load and prepare property table on section change.
	Don't disassemble literals. Don't disassemble instructions that
	cross property table boundaries.

1 files changed, 194 insertions, 22 deletions

diff --git a/opcodes/xtensa-dis.c b/opcodes/xtensa-dis.c
index d78f9d5..c11cf06 100644
--- a/opcodes/xtensa-dis.c
+++ b/opcodes/xtensa-dis.c
@@ -27,6 +27,8 @@
 #include "xtensa-isa.h"
 #include "ansidecl.h"
 #include "libiberty.h"
+#include "bfd.h"
+#include "elf/xtensa.h"
 #include "disassemble.h"
 
 #include <setjmp.h>
@@ -43,8 +45,119 @@ struct dis_private
 {
   bfd_byte *byte_buf;
   OPCODES_SIGJMP_BUF bailout;
+  /* Persistent fields, valid for last_section only.  */
+  asection *last_section;
+  property_table_entry *insn_table_entries;
+  int insn_table_entry_count;
+  /* Cached property table search position.  */
+  bfd_vma insn_table_cur_addr;
+  int insn_table_cur_idx;
 };
 
+static void
+xtensa_coalesce_insn_tables (struct dis_private *priv)
+{
+  const int mask = ~(XTENSA_PROP_DATA | XTENSA_PROP_NO_TRANSFORM);
+  int count = priv->insn_table_entry_count;
+  int i, j;
+
+  /* Loop over all entries, combining adjacent ones that differ only in
+     the flag bits XTENSA_PROP_DATA and XTENSA_PROP_NO_TRANSFORM.  */
+
+  for (i = j = 0; j < count; ++i)
+    {
+      property_table_entry *entry = priv->insn_table_entries + i;
+
+      *entry = priv->insn_table_entries[j];
+
+      for (++j; j < count; ++j)
+	{
+	  property_table_entry *next = priv->insn_table_entries + j;
+	  int fill = xtensa_compute_fill_extra_space (entry);
+	  int size = entry->size + fill;
+
+	  if (entry->address + size == next->address)
+	    {
+	      int entry_flags = entry->flags & mask;
+	      int next_flags = next->flags & mask;
+
+	      if (next_flags == entry_flags)
+		entry->size = next->address - entry->address + next->size;
+	      else
+		break;
+	    }
+	  else
+	    {
+	      break;
+	    }
+	}
+    }
+  priv->insn_table_entry_count = i;
+}
+
+static property_table_entry *
+xtensa_find_table_entry (bfd_vma memaddr, struct disassemble_info *info)
+{
+  struct dis_private *priv = (struct dis_private *) info->private_data;
+  int i;
+
+  if (priv->insn_table_entries == NULL
+      || priv->insn_table_entry_count < 0)
+    return NULL;
+
+  if (memaddr < priv->insn_table_cur_addr)
+    priv->insn_table_cur_idx = 0;
+
+  for (i = priv->insn_table_cur_idx; i < priv->insn_table_entry_count; ++i)
+    {
+      property_table_entry *block = priv->insn_table_entries + i;
+
+      if (block->size != 0)
+	{
+	  if ((memaddr >= block->address
+	       && memaddr < block->address + block->size)
+	      || memaddr < block->address)
+	    {
+	      priv->insn_table_cur_addr = memaddr;
+	      priv->insn_table_cur_idx = i;
+	      return block;
+	    }
+	}
+    }
+  return NULL;
+}
+
+/* Check whether an instruction crosses an instruction block boundary
+   (according to property tables).
+   If it does, return 0 (doesn't fit), else return 1.  */
+
+static int
+xtensa_instruction_fits (bfd_vma memaddr, int size,
+			 property_table_entry *insn_block)
+{
+  unsigned max_size;
+
+  /* If no property table info, assume it fits.  */
+  if (insn_block == NULL || size <= 0)
+    return 1;
+
+  /* If too high, limit nextstop by the next insn address.  */
+  if (insn_block->address > memaddr)
+    {
+      /* memaddr is not in an instruction block, but is followed by one.  */
+      max_size = insn_block->address - memaddr;
+    }
+  else
+    {
+      /* memaddr is in an instruction block, go no further than the end.  */
+      max_size = insn_block->address + insn_block->size - memaddr;
+    }
+
+  /* Crossing a boundary, doesn't "fit".  */
+  if ((unsigned)size > max_size)
+    return 0;
+  return 1;
+}
 
 static int
 fetch_data (struct disassemble_info *info, bfd_vma memaddr)
@@ -53,6 +166,8 @@ fetch_data (struct disassemble_info *info, bfd_vma memaddr)
   struct dis_private *priv = (struct dis_private *) info->private_data;
   int insn_size = xtensa_isa_maxlength (xtensa_default_isa);
 
+  insn_size = MAX (insn_size, 4);
+
   /* Read the maximum instruction size, padding with zeros if we go past
      the end of the text section.  This code will automatically adjust
      length when we hit the end of the buffer.  */
@@ -140,11 +255,12 @@ print_insn_xtensa (bfd_vma memaddr, struct disassemble_info *info)
   xtensa_isa isa;
   xtensa_opcode opc;
   xtensa_format fmt;
-  struct dis_private priv;
+  static struct dis_private priv;
   static bfd_byte *byte_buf = NULL;
   static xtensa_insnbuf insn_buffer = NULL;
   static xtensa_insnbuf slot_buffer = NULL;
-  int first, first_slot, valid_insn;
+  int first, first_slot, valid_insn = 0;
+  property_table_entry *insn_block;
 
   if (!xtensa_default_isa)
     xtensa_default_isa = xtensa_isa_init (0, 0);
@@ -175,6 +291,49 @@ print_insn_xtensa (bfd_vma memaddr, struct disassemble_info *info)
   priv.byte_buf = byte_buf;
 
   info->private_data = (void *) &priv;
+
+  /* Prepare instruction tables.  */
+
+  if (info->section != NULL)
+    {
+      asection *section = info->section;
+
+      if (priv.last_section != section)
+	{
+	  bfd *abfd = section->owner;
+
+	  if (priv.last_section != NULL)
+	    {
+	      /* Reset insn_table_entries.  */
+	      priv.insn_table_entry_count = 0;
+	      if (priv.insn_table_entries)
+		free (priv.insn_table_entries);
+	      priv.insn_table_entries = NULL;
+	    }
+	  priv.last_section = section;
+
+	  /* Read insn_table_entries.  */
+	  priv.insn_table_entry_count =
+	    xtensa_read_table_entries (abfd, section,
+				       &priv.insn_table_entries,
+				       XTENSA_PROP_SEC_NAME, FALSE);
+	  if (priv.insn_table_entry_count == 0)
+	    {
+	      if (priv.insn_table_entries)
+		free (priv.insn_table_entries);
+	      priv.insn_table_entries = NULL;
+	      /* Backwards compatibility support.  */
+	      priv.insn_table_entry_count =
+		xtensa_read_table_entries (abfd, section,
+					   &priv.insn_table_entries,
+					   XTENSA_INSN_SEC_NAME, FALSE);
+	    }
+	  priv.insn_table_cur_idx = 0;
+	  xtensa_coalesce_insn_tables (&priv);
+	}
+      /* Else nothing to do, same section as last time.  */
+    }
+
   if (OPCODES_SIGSETJMP (priv.bailout) != 0)
       /* Error return.  */
       return -1;
@@ -187,36 +346,49 @@ print_insn_xtensa (bfd_vma memaddr, struct disassemble_info *info)
   /* Fetch the maximum size instruction.  */
   bytes_fetched = fetch_data (info, memaddr);
 
-  /* Copy the bytes into the decode buffer.  */
-  memset (insn_buffer, 0, (xtensa_insnbuf_size (isa) *
-			   sizeof (xtensa_insnbuf_word)));
-  xtensa_insnbuf_from_chars (isa, insn_buffer, priv.byte_buf, bytes_fetched);
+  insn_block = xtensa_find_table_entry (memaddr, info);
 
-  fmt = xtensa_format_decode (isa, insn_buffer);
-  if (fmt == XTENSA_UNDEFINED
-      || ((size = xtensa_format_length (isa, fmt)) > bytes_fetched))
-    valid_insn = 0;
-  else
+  if (!insn_block || (insn_block->flags & XTENSA_PROP_INSN))
     {
-      /* Make sure all the opcodes are valid.  */
-      valid_insn = 1;
-      nslots = xtensa_format_num_slots (isa, fmt);
-      for (n = 0; n < nslots; n++)
+      /* Copy the bytes into the decode buffer.  */
+      memset (insn_buffer, 0, (xtensa_insnbuf_size (isa) *
+			       sizeof (xtensa_insnbuf_word)));
+      xtensa_insnbuf_from_chars (isa, insn_buffer, priv.byte_buf,
+				 bytes_fetched);
+
+      fmt = xtensa_format_decode (isa, insn_buffer);
+      if (fmt != XTENSA_UNDEFINED
+	  && ((size = xtensa_format_length (isa, fmt)) <= bytes_fetched)
+	  && xtensa_instruction_fits (memaddr, size, insn_block))
 	{
-	  xtensa_format_get_slot (isa, fmt, n, insn_buffer, slot_buffer);
-	  if (xtensa_opcode_decode (isa, fmt, n, slot_buffer)
-	      == XTENSA_UNDEFINED)
+	  /* Make sure all the opcodes are valid.  */
+	  valid_insn = 1;
+	  nslots = xtensa_format_num_slots (isa, fmt);
+	  for (n = 0; n < nslots; n++)
 	    {
-	      valid_insn = 0;
-	      break;
+	      xtensa_format_get_slot (isa, fmt, n, insn_buffer, slot_buffer);
+	      if (xtensa_opcode_decode (isa, fmt, n, slot_buffer)
+		  == XTENSA_UNDEFINED)
+		{
+		  valid_insn = 0;
+		  break;
+		}
 	    }
 	}
     }
 
   if (!valid_insn)
     {
-      (*info->fprintf_func) (info->stream, ".byte %#02x", priv.byte_buf[0]);
-      return 1;
+      if (insn_block && (insn_block->flags & XTENSA_PROP_LITERAL)
+	  && (memaddr & 3) == 0 && bytes_fetched >= 4)
+	{
+	  return 4;
+	}
+      else
+	{
+	  (*info->fprintf_func) (info->stream, ".byte %#02x", priv.byte_buf[0]);
+	  return 1;
+	}
     }
 
   if (nslots > 1)