[OPCODE][AARCH64]Check mapping symbol while backward searching for IT block

[Renlin Li <renlin dot li at arm dot com>]

Hi all,

For the following simple assembly code.

        .text
        .thumb
        .syntax unified
        .thumb_func
f:
        nop.w
        .long 0xbf080000
        nop.w

When objdumped, the following code assembly will be generated.

   0:   f3af 8000       nop.w
   4:   bf080000        .word   0xbf080000
   8:   f3af 8000       nopeq.w

The instruction at pc=0x8 is treated as conditional executed instruction 
within an IT block. This is because objdump misinterprets data (at 
pc=0x4) as an IT instruction.
During the backward search for a proper IT instruction, mapping state 
for the current instruction is not checked.


In this patch, I create a new function mapping_symbol_for_insn to search 
the mapping state given an addr.
It's used in find_ifthen_state to further guard the check for an IT 
instruction.

A new testcase is also added. Binutils checked without any new issues. 
Is Okay to commit on trunk?


Kind regards,
Renlin Li




opcodes/ChangeLog:

2015-09-10  Renlin Li  <renlin.li@arm.com>

    * arm-dis.c (mapping_symbol_for_insn): New function.
    (find_ifthen_state): Call mapping_symbol_for_insn().



gas/testsuite/ChangeLog:

2015-09-10  Renlin Li  <renlin.li@arm.com>

    * gas/arm/thumb2_it_search.d: New.
    * gas/arm/thumb2_it_search.s: New.


commit 347a76f708bfb31b38ce787bd444005412655ae0
Author: Renlin Li <renlin.li@arm.com>
Date:   Thu Sep 10 16:13:22 2015 +0100

    tmp
    
    Change-Id: I74905754d21022ba9513f12649e80cd65d4425a9

diff --git a/gas/testsuite/gas/arm/thumb2_it_search.d b/gas/testsuite/gas/arm/thumb2_it_search.d
new file mode 100644
index 0000000..6758ef8
--- /dev/null
+++ b/gas/testsuite/gas/arm/thumb2_it_search.d
@@ -0,0 +1,12 @@
+#name: 32-bit Thumb conditional instructions backward search
+#as: -march=armv6kt2
+#skip: *-*-*aout*
+#source: thumb2_it_search.s
+#objdump: -dr --prefix-addresses --show-raw-insn
+
+.*: +file format .*arm.*
+
+Disassembly of section .text:
+0+0 <[^>]+> f3af 8000 	nop.w
+0+4 <[^>]+> bf080000 	.word	0xbf080000
+0+8 <[^>]+> f3af 8000 	nop.w
diff --git a/gas/testsuite/gas/arm/thumb2_it_search.s b/gas/testsuite/gas/arm/thumb2_it_search.s
new file mode 100644
index 0000000..a29cb51
--- /dev/null
+++ b/gas/testsuite/gas/arm/thumb2_it_search.s
@@ -0,0 +1,8 @@
+	.text
+	.thumb
+	.syntax unified
+	.thumb_func
+f:
+	nop.w
+	.long 0xbf080000
+	nop.w
diff --git a/opcodes/arm-dis.c b/opcodes/arm-dis.c
index 430da08..6a097f5 100644
--- a/opcodes/arm-dis.c
+++ b/opcodes/arm-dis.c
@@ -5930,6 +5930,10 @@ parse_disassembler_options (char *options)
     }
 }
 
+static bfd_boolean
+mapping_symbol_for_insn (bfd_vma pc, struct disassemble_info *info,
+			 enum map_type *map_symbol);
+
 /* Search back through the insn stream to determine if this instruction is
    conditionally executed.  */
 
@@ -5992,9 +5996,15 @@ find_ifthen_state (bfd_vma pc,
 	}
       if ((insn & 0xff00) == 0xbf00 && (insn & 0xf) != 0)
 	{
-	  /* This could be an IT instruction.  */
-	  seen_it = insn;
-	  it_count = count >> 1;
+	  enum map_type type = MAP_ARM;
+	  bfd_boolean found = mapping_symbol_for_insn (addr, info, &type);
+
+	  if (!found || (found && type == MAP_THUMB))
+	    {
+	      /* This could be an IT instruction.  */
+	      seen_it = insn;
+	      it_count = count >> 1;
+	    }
 	}
       if ((insn & 0xf800) >= 0xe800)
 	count++;
@@ -6078,6 +6088,71 @@ get_sym_code_type (struct disassemble_info *info,
   return FALSE;
 }
 
+/* Search the mapping symbol state for instruction at pc.  This is only
+   applicable for elf target.
+
+   There is an assumption Here, info->private_data contains the correct AND
+   up-to-date information about current scan process.  The information will be
+   used to speed this search process.
+
+   Return TRUE if the mapping state can be determined, and map_symbol
+   will be updated accordingly.  Otherwise, return FALSE.  */
+
+static bfd_boolean
+mapping_symbol_for_insn (bfd_vma pc, struct disassemble_info *info,
+			 enum map_type *map_symbol)
+{
+  bfd_vma addr;
+  int n, start = 0;
+  bfd_boolean found = FALSE;
+  enum map_type type = MAP_ARM;
+  struct arm_private_data *private_data;
+
+  if (info->private_data == NULL || info->symtab_size == 0
+      || bfd_asymbol_flavour (*info->symtab) != bfd_target_elf_flavour)
+    return FALSE;
+
+  private_data = info->private_data;
+  if (pc == 0)
+    start = 0;
+  else
+    start = private_data->last_mapping_sym;
+
+  start = (start == -1)? 0 : start;
+  addr = bfd_asymbol_value (info->symtab[start]);
+
+  if (pc >= addr)
+    {
+      if (get_map_sym_type (info, start, &type))
+      found = TRUE;
+    }
+  else
+    {
+      for (n = start - 1; n >= 0; n--)
+	{
+	  if (get_map_sym_type (info, n, &type))
+	    {
+	      found = TRUE;
+	      break;
+	    }
+	}
+    }
+
+  /* No mapping symbols were found.  A leading $d may be
+     omitted for sections which start with data; but for
+     compatibility with legacy and stripped binaries, only
+     assume the leading $d if there is at least one mapping
+     symbol in the file.  */
+  if (!found && private_data->has_mapping_symbols == 1)
+    {
+      type = MAP_DATA;
+      found = TRUE;
+    }
+
+  *map_symbol = type;
+  return found;
+}
+
 /* Given a bfd_mach_arm_XXX value, this function fills in the fields
    of the supplied arm_feature_set structure with bitmasks indicating
    the support base architectures and coprocessor extensions.