[PATCH][Binutils][Arm] Fix disassembler crashing on -b binary when thumb file and thumb not forced.

[Tamar Christina <tamar dot christina at arm dot com>]

Hi All,

The disassembler for Arm has some aborts in it in places it assumes can never
be reached.  Under normal circumstances they indeed cannot be reached because
the right options are selected from the ARM attributes in the ELF file.

However when disassembling with -b binary then if you do not get the options
right the disassembler just aborts.  This changes it so it just prints how it
was trying to interpret the instruction and prints UNKNOWN instructions next to it.

This way the user has an idea of what's going.

build on native hardware and regtested on
  arm-none-eabi, arm-none-eabi (64 bit host),
  arm-none-linux-gnueabihf, arm-none-linux-gnueabihf (64 bit host)

Cross-compiled and regtested on
  arm-none-eabi, armeb-none-eabi

and no issues.

Ok for master? and for backport to binutils-2.31?

Thanks,
Tamar

gas/ChangeLog:
2018-10-17  Tamar Christina  <tamar.christina@arm.com>

	* testsuite/gas/arm/undefined-insn-arm.d: New test.
	* testsuite/gas/arm/undefined-insn-thumb.d: New test.
	* testsuite/gas/arm/undefined-insn.s: New test.

opcodes/ChangeLog:
2018-10-17  Tamar Christina  <tamar.christina@arm.com>

	* arm-dis.c (UNKNOWN_INSTRUCTION_32BIT): Format specifier for arm mode.
	(UNKNOWN_INSTRUCTION_16BIT): Format specifier for thumb mode.
	(print_insn_arm, print_insn_thumb16, print_insn_thumb32): Use them.

-- 

diff --git a/gas/testsuite/gas/arm/undefined-insn-arm.d b/gas/testsuite/gas/arm/undefined-insn-arm.d
new file mode 100644
index 0000000000000000000000000000000000000000..265a507d3b722332d3dc1f501d54f1cb79754682
--- /dev/null
+++ b/gas/testsuite/gas/arm/undefined-insn-arm.d
@@ -0,0 +1,5 @@
+#name: Undefined binary printing in arm mode
+#skip: *-unknown-pe *-*-vxworks
+#source: undefined-insn.s
+#objdump: -D -b binary -m armv7e-m
+#...
diff --git a/gas/testsuite/gas/arm/undefined-insn-thumb.d b/gas/testsuite/gas/arm/undefined-insn-thumb.d
new file mode 100644
index 0000000000000000000000000000000000000000..72385f0818f3dec33d409561b40559779feff172
--- /dev/null
+++ b/gas/testsuite/gas/arm/undefined-insn-thumb.d
@@ -0,0 +1,5 @@
+#name: Undefined binary printing in thumb mode
+#skip: *-unknown-pe *-*-vxworks
+#source: undefined-insn.s
+#objdump: -D -b binary -m armv7e-m -M force-thumb
+#...
diff --git a/gas/testsuite/gas/arm/undefined-insn.s b/gas/testsuite/gas/arm/undefined-insn.s
new file mode 100644
index 0000000000000000000000000000000000000000..cf59a03d1d83790e382bdb4b93a2b282504e95bc
--- /dev/null
+++ b/gas/testsuite/gas/arm/undefined-insn.s
@@ -0,0 +1 @@
+	.inst 0xffffffff
diff --git a/opcodes/arm-dis.c b/opcodes/arm-dis.c
index f22a78f70d551bf8033a2d2b5b9b44243fd020c0..f0b90510c60071e4fbd835fbed3adce1aa0189d7 100644
--- a/opcodes/arm-dis.c
+++ b/opcodes/arm-dis.c
@@ -141,6 +141,8 @@ enum opcode_sentinel_enum
 } opcode_sentinels;
 
 #define UNDEFINED_INSTRUCTION      "\t\t; <UNDEFINED> instruction: %0-31x"
+#define UNKNOWN_INSTRUCTION_32BIT  "\t\t; <UNDEFINED> instruction: %08x"
+#define UNKNOWN_INSTRUCTION_16BIT  "\t\t; <UNDEFINED> instruction: %04x"
 #define UNPREDICTABLE_INSTRUCTION  "\t; <UNPREDICTABLE>"
 
 /* Common coprocessor opcodes shared between Arm and Thumb-2.  */
@@ -5194,7 +5196,8 @@ print_insn_arm (bfd_vma pc, struct disassemble_info *info, long given)
 	  return;
 	}
     }
-  abort ();
+  func (stream, UNKNOWN_INSTRUCTION_32BIT, (unsigned)given);
+  return;
 }
 
 /* Print one 16-bit Thumb instruction from PC on INFO->STREAM.  */
@@ -5465,7 +5468,8 @@ print_insn_thumb16 (bfd_vma pc, struct disassemble_info *info, long given)
       }
 
   /* No match.  */
-  abort ();
+  func (stream, UNKNOWN_INSTRUCTION_16BIT, (unsigned)given);
+  return;
 }
 
 /* Return the name of an V7M special register.  */
@@ -6089,7 +6093,8 @@ print_insn_thumb32 (bfd_vma pc, struct disassemble_info *info, long given)
       }
 
   /* No match.  */
-  abort ();
+  func (stream, UNKNOWN_INSTRUCTION_32BIT, (unsigned)given);
+  return;
 }
 
 /* Print data bytes on INFO->STREAM.  */