bfd: xtensa: ignore overflow in hight part of const16 relocation

32-bit constants loaded by two const16 opcodes that involve relocation
(e.g. calculated as a sum of a symbol and a constant) may overflow,
resulting in linking error with the following message:

  dangerous relocation: const16: cannot encode: (_start+0x70000000)

They should wrap around instead. Limit const16 opcode immediate field to
16 least significant bits to implement this wrap around.

bfd/
2018-12-11  Max Filippov  <jcmvbkbc@gmail.com>

	* elf32-xtensa.c (elf_xtensa_do_reloc): Limit const16 opcode
	immediate field to 16 least significant bits.

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index b88fe7e..9acd28d 100644 (file)
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,8 @@
+2018-12-11  Max Filippov  <jcmvbkbc@gmail.com>
+
+       * elf32-xtensa.c (elf_xtensa_do_reloc): Limit const16 opcode
+       immediate field to 16 least significant bits.
+
 2018-12-11  H.J. Lu  <hongjiu.lu@intel.com>
 
        * elf32-xc16x.c (elf32_xc16x_rtype_to_howto): New function.

diff --git a/bfd/elf32-xtensa.c b/bfd/elf32-xtensa.c
index cf085b7..de960cd 100644 (file)
--- a/bfd/elf32-xtensa.c
+++ b/bfd/elf32-xtensa.c
@@ -1957,8 +1957,9 @@ elf_xtensa_do_reloc (reloc_howto_type *howto,
        }
       else if (opcode == get_const16_opcode ())
        {
-         /* ALT used for high 16 bits.  */
-         newval = relocation >> 16;
+         /* ALT used for high 16 bits.
+            Ignore 32-bit overflow.  */
+         newval = (relocation >> 16) & 0xffff;
          opnd = 1;
        }
       else