[Patch, avr] Fix PR 20221 - adjust syms and relocs only if relax shrunk section

[Senthil Kumar Selvaraj]

Tristan Gingold writes:

>> On 10 Jun 2016, at 11:25, Senthil Kumar Selvaraj <senthil_kumar.selvaraj@atmel.com> wrote:
>> 
>> 
>> Denis Chertykov writes:
>> 
>>> 2016-06-08 11:53 GMT+03:00 Senthil Kumar Selvaraj
>>> <senthil_kumar.selvaraj@atmel.com>:
>>>> Hi,
>>>> 
>>>>  This patch fixes an edge case in linker relaxation that causes symbol
>>>>  values to be computed incorrectly in the presence of align directives
>>>>  in input source code.
>>>> 
>>>>  As the below testcase demonstrates, for code like
>>>> 
>>>> _start:
>>>>        CALL    dest
>>>>        .align  1
>>>> dest:
>>>>        NOP
>>>> 
>>>>  where the bytes to be deleted (CALL to RCALL, 2 bytes) are adjacent to an
>>>>  alignment boundary, no deletion happens - the prop record handling
>>>>  merely overwrites the to-be-deleted-bytes with NOPs. AFAICT, this is
>>>>  ok - eventually, relaxation sees that the padding is unnecessary and
>>>>  strips the NOPs away.
>>>> 
>>>>  However, the rest of elf32_avr_relax_delete_bytes runs with the assumption
>>>>  that the bytes have been deleted, and this causes symbol values and/or
>>>>  reloc offsets to be decremented even if nothing has moved. dest, in the
>>>>  above testcase, gets decremented by 2 even when the gap got alignment
>>>>  padded, and then again when the padding was removed - it ends up
>>>>  getting adjusted down twice.
>>>> 
>>>>  The patch fixes this by recording whether shrinking actually occurred,
>>>>  and then skipping the reloc offset/sym value adjutment if it did
>>>>  not. There's also a testcase that fails with master (and 2.26) that
>>>>  passes with this patch.
>>>> 
>>>>  Ok for master? Can I backport to 2.26 branch if ok?
>>>> 
>>>> Regards
>>>> Senthil
>>>> 
>>>> 
>>>> bfd/ChangeLog
>>>> 
>>>> 2016-06-08  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>
>>>> 
>>>>        PR ld/20221
>>>>        * elf32-avr.c (elf32_avr_relax_delete_bytes): Adjust syms
>>>>  and relocs only if shrinking occurred.
>>>> 
>>>> ld/ChangeLog
>>>> 
>>>> 2016-06-08  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>
>>>> 
>>>>        PR ld/20221
>>>>        * testsuite/ld-avr/avr-prop-5.d: New.
>>>>        * testsuite/ld-avr/avr-prop-5.s: New.
>>>> 
>>>> 
>>> 
>>> Committed.
>> 
>> Is this ok for binutils-2_26-branch?
>
> Yes.

bfd/ChangeLog

2016-06-13  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>

       Backport from master
       2016-06-08  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>

       PR ld/20221
       * elf32-avr.c (elf32_avr_relax_delete_bytes): Adjust syms
       and relocs only if shrinking occurred.

ld/ChangeLog

2016-06-13  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>

       Backport from master
       2016-06-08  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>

       PR ld/20221
       * testsuite/ld-avr/avr-prop-5.d: New.
       * testsuite/ld-avr/avr-prop-5.s: New.


Committed to binutils-2_26-branch.

Regards
Senthil