[binutils-gdb] bfd: xtensa: ignore overflow in hight part of const16 relocation

[Max Filippov]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=00863b8e40a0afd0daf0925acf3f7c794dfd9c73

commit 00863b8e40a0afd0daf0925acf3f7c794dfd9c73
Author: Max Filippov <jcmvbkbc@gmail.com>
Date:   Fri Dec 7 12:59:04 2018 -0800

    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:
---
 bfd/ChangeLog      | 5 +++++
 bfd/elf32-xtensa.c | 5 +++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index b88fe7e..9acd28d 100644
--- 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
--- 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