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Re: [Patch, avr] Fix PR 20221 - adjust syms and relocs only if relax shrunk section
- From: Denis Chertykov <chertykov at gmail dot com>
- To: Senthil Kumar Selvaraj <senthil_kumar dot selvaraj at atmel dot com>
- Cc: "binutils at sourceware dot org" <binutils at sourceware dot org>, Andrew Burgess <andrew dot burgess at embecosm dot com>, Nick Clifton <nickc at redhat dot com>
- Date: Thu, 9 Jun 2016 19:20:06 +0300
- Subject: Re: [Patch, avr] Fix PR 20221 - adjust syms and relocs only if relax shrunk section
- Authentication-results: sourceware.org; auth=none
- References: <8760tkawob dot fsf at atmel dot com>
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.