Enhance the disassembler so that it will reliably determine whether a reloc applies to the middle of the next insn.

	PR 24907
binutils* objdump.c (null_print): New function.
	(disassemble_bytes): Delete previous_octets local and replace with
	a test of the max_reloc_offset_into_insn field of the
	bfd_arch_info structure.  If a reloc is a potential match for the
	next insn, then perform a dummy disassembly in order to calculate
	its real length.

bfd	* archures.c (bfd_arch_info_type): Add max_reloc_offset_into_insn
	field.
	(bfd_default_arch_struct): Initialise the new field.
	* bfd-in2.h: Regenerate.
	* cpu-aarch64.c: Initialise the new field.
	* cpu-alpha.c: Likewise.
	* cpu-arc.c: Likewise.
	* cpu-arm.c: Likewise.
	* cpu-avr.c: Likewise.
	* cpu-bfin.c: Likewise.
	* cpu-bpf.c: Likewise.
	* cpu-cr16.c: Likewise.
	* cpu-cr16c.c: Likewise.
	* cpu-cris.c: Likewise.
	* cpu-crx.c: Likewise.
	* cpu-csky.c: Likewise.
	* cpu-d10v.c: Likewise.
	* cpu-d30v.c: Likewise.
	* cpu-dlx.c: Likewise.
	* cpu-epiphany.c: Likewise.
	* cpu-fr30.c: Likewise.
	* cpu-frv.c: Likewise.
	* cpu-ft32.c: Likewise.
	* cpu-h8300.c: Likewise.
	* cpu-hppa.c: Likewise.
	* cpu-i386.c: Likewise.
	* cpu-ia64.c: Likewise.
	* cpu-iamcu.c: Likewise.
	* cpu-ip2k.c: Likewise.
	* cpu-iq2000.c: Likewise.
	* cpu-k1om.c: Likewise.
	* cpu-l1om.c: Likewise.
	* cpu-lm32.c: Likewise.
	* cpu-m10200.c: Likewise.
	* cpu-m10300.c: Likewise.
	* cpu-m32c.c: Likewise.
	* cpu-m32r.c: Likewise.
	* cpu-m68hc11.c: Likewise.
	* cpu-m68hc12.c: Likewise.
	* cpu-m68k.c: Likewise.
	* cpu-m9s12x.c: Likewise.
	* cpu-m9s12xg.c: Likewise.
	* cpu-mcore.c: Likewise.
	* cpu-mep.c: Likewise.
	* cpu-metag.c: Likewise.
	* cpu-microblaze.c: Likewise.
	* cpu-mips.c: Likewise.
	* cpu-mmix.c: Likewise.
	* cpu-moxie.c: Likewise.
	* cpu-msp430.c: Likewise.
	* cpu-mt.c: Likewise.
	* cpu-nds32.c: Likewise.
	* cpu-nfp.c: Likewise.
	* cpu-nios2.c: Likewise.
	* cpu-ns32k.c: Likewise.
	* cpu-or1k.c: Likewise.
	* cpu-pdp11.c: Likewise.
	* cpu-pj.c: Likewise.
	* cpu-plugin.c: Likewise.
	* cpu-powerpc.c: Likewise.
	* cpu-pru.c: Likewise.
	* cpu-riscv.c: Likewise.
	* cpu-rl78.c: Likewise.
	* cpu-rs6000.c: Likewise.
	* cpu-rx.c: Likewise.
	* cpu-s12z.c: Likewise.
	* cpu-s390.c: Likewise.
	* cpu-score.c: Likewise.
	* cpu-sh.c: Likewise.
	* cpu-sparc.c: Likewise.
	* cpu-spu.c: Likewise.
	* cpu-tic30.c: Likewise.
	* cpu-tic4x.c: Likewise.
	* cpu-tic54x.c: Likewise.
	* cpu-tic6x.c: Likewise.
	* cpu-tic80.c: Likewise.
	* cpu-tilegx.c: Likewise.
	* cpu-tilepro.c: Likewise.
	* cpu-v850.c: Likewise.
	* cpu-v850_rh850.c: Likewise.
	* cpu-vax.c: Likewise.
	* cpu-visium.c: Likewise.
	* cpu-wasm32.c: Likewise.
	* cpu-xc16x.c: Likewise.
	* cpu-xgate.c: Likewise.
	* cpu-xstormy16.c: Likewise.
	* cpu-xtensa.c: Likewise.
	* cpu-z80.c: Likewise.
	* cpu-z8k.c: Likewise.

gas	* testsuite/gas/arm/pr24907.s: New test.
	* testsuite/gas/arm/pr24907.d: Expected disassembly.

2 files changed, 45 insertions, 15 deletions

diff --git a/binutils/ChangeLog b/binutils/ChangeLog
index 5e8e03d6048..7ccf842955b 100644
--- a/binutils/ChangeLog
+++ b/binutils/ChangeLog
@@ -1,3 +1,13 @@
+2019-09-10  Nick Clifton  <nickc@redhat.com>
+
+	PR 24907
+	* objdump.c (null_print): New function.
+	(disassemble_bytes): Delete previous_octets local and replace with
+	a test of the max_reloc_offset_into_insn field of the
+	bfd_arch_info structure.  If a reloc is a potential match for the
+	next insn, then perform a dummy disassembly in order to calculate
+	its real length.
+
 2019-09-09  Phil Blundell  <pb@pbcl.net>
 
 	binutils 2.33 branch created.
diff --git a/binutils/objdump.c b/binutils/objdump.c
index 33d5d72d3d5..2303fe4abf8 100644
--- a/binutils/objdump.c
+++ b/binutils/objdump.c
@@ -1836,6 +1836,12 @@ objdump_sprintf (SFILE *f, const char *format, ...)
 
 #define DEFAULT_SKIP_ZEROES_AT_END 3
 
+static int
+null_print (const void * stream ATTRIBUTE_UNUSED, const char * format ATTRIBUTE_UNUSED, ...)
+{
+  return 1;
+}
+
 /* Disassemble some data in memory between given values.  */
 
 static void
@@ -1903,10 +1909,7 @@ disassemble_bytes (struct disassemble_info * inf,
     {
       bfd_vma z;
       bfd_boolean need_nl = FALSE;
-      int previous_octets;
 
-      /* Remember the length of the previous instruction.  */
-      previous_octets = octets;
       octets = 0;
 
       /* Make sure we don't use relocs from previous instructions.  */
@@ -1990,26 +1993,43 @@ disassemble_bytes (struct disassemble_info * inf,
 		  && *relppp < relppend)
 		{
 		  bfd_signed_vma distance_to_rel;
+		  int insn_size = 0;
 
 		  distance_to_rel = (**relppp)->address
 		    - (rel_offset + addr_offset);
 
+		  if (distance_to_rel > 0
+		      && aux->abfd->arch_info->max_reloc_offset_into_insn <= distance_to_rel)
+		    {
+		      /* This reloc *might* apply to the current insn,
+			 starting somewhere inside it.  Discover the length
+			 of the current insn so that the check below will
+			 work.  */
+		      if (insn_width)
+			insn_size = insn_width;
+		      else
+			{
+			  /* We find the length by calling the dissassembler
+			     function with a dummy print handler.  This should
+			     work unless the disassembler is not expecting to
+			     be called multiple times for the same address.
+
+			     This does mean disassembling the instruction
+			     twice, but we only do this when there is a high
+			     probability that there is a reloc that will
+			     affect the instruction.  */
+			  inf->fprintf_func = (fprintf_ftype) null_print;
+			  insn_size = disassemble_fn (section->vma
+						      + addr_offset, inf);
+			  inf->fprintf_func = (fprintf_ftype) objdump_sprintf;
+			}
+		    }
+
 		  /* Check to see if the current reloc is associated with
 		     the instruction that we are about to disassemble.  */
 		  if (distance_to_rel == 0
-		      /* FIXME: This is wrong.  We are trying to catch
-			 relocs that are addressed part way through the
-			 current instruction, as might happen with a packed
-			 VLIW instruction.  Unfortunately we do not know the
-			 length of the current instruction since we have not
-			 disassembled it yet.  Instead we take a guess based
-			 upon the length of the previous instruction.  The
-			 proper solution is to have a new target-specific
-			 disassembler function which just returns the length
-			 of an instruction at a given address without trying
-			 to display its disassembly. */
 		      || (distance_to_rel > 0
-			  && distance_to_rel < (bfd_signed_vma) (previous_octets/ opb)))
+			  && distance_to_rel < (bfd_signed_vma) (insn_size / opb)))
 		    {
 		      inf->flags |= INSN_HAS_RELOC;
 		      aux->reloc = **relppp;