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Re: [gold][aarch64] PR gold/19163: zero-out ABS64/32/16/ in .rela.dyn.

From: Cary Coutant <ccoutant at gmail dot com>
To: Han Shen <shenhan at google dot com>
Cc: binutils <binutils at sourceware dot org>, Luis Lozano <llozano at google dot com>, Dimitry Ivanov <dimitry at google dot com>
Date: Thu, 5 Nov 2015 12:28:10 -0800
Subject: Re: [gold][aarch64] PR gold/19163: zero-out ABS64/32/16/ in .rela.dyn.
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References: <CACkGtrgmYrTDr+VdeF5SE2sNY_mzGFTJ+g_n8Rxz_gcy6uzFpg at mail dot gmail dot com> <CACkGtrgGbyU=Yzjf796ah6Xxc+V0Q-EnBw1x+fFovAq9DZOa0Q at mail dot gmail dot com> <CAJimCsEFW52zC0tXOUhdqY7miCX6VG3mkA4gTfVQZ2zB0yXLjg at mail dot gmail dot com> <CACkGtrja4SjL-pPeqdUm54QnmgYsKwexzbfD5T1Fx_4dCtXp_A at mail dot gmail dot com>

> +      if (!parameters->options().apply_dynamic_relocs()
>
>>> Han: we need to test if gsym is NULL, in one of my cases, gsym is NULL and gold crashes.

Yes, sorry, I should have caught that.

>
> +          && parameters->options().output_is_position_independent()
> +          && gsym->needs_dynamic_reloc(reloc_property->reference_flags())
> +          && !gsym->can_use_relative_reloc(false))
> +        // We have generated an absolute dynamic relocation, so do not
> +        // apply the relocation statically. (Works around bugs in older
> +        // Android dynamic linkers.)
>
>>> Han: do we need to explicitly write zeros to this location instead of just do nothing? (Although I've checked the values of the resulting binary, the location contains all zeros)

Not as long as the compiler writes zeroes (which it should).

I've committed the attached patch.

-cary

2015-11-05  Cary Coutant  <ccoutant@gmail.com>

gold/
        PR gold/19163
        * aarch64.cc (Target_aarch64::Relocate::relocate): Don't apply
        certain relocations if --no-apply-dynamic-relocs is set.
        * options.h (--apply-dynamic-relocs): New aarch64-specific option.

Attachment: pr19163-3.patch
Description: Binary data

References:
- Re: [gold][aarch64] PR gold/19163: zero-out ABS64/32/16/ in .rela.dyn.
  - From: Han Shen

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