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Re: [PATCH] elf/get-dynamic-info.h: fix early GNU_HASH processing on ia64

From: Sergei Trofimovich <slyich at gmail dot com>
To: Florian Weimer <fweimer at redhat dot com>
Cc: libc-alpha at sourceware dot org, Andreas Schwab <schwab at suse dot de>, Richard Biener <rguenth at gcc dot gnu dot org>, Eric Botcazou <ebotcazou at gcc dot gnu dot org>, Dennis Schridde <devurandom at gmx dot net>, Sergei Trofimovich <siarheit at google dot com>
Date: Mon, 28 Dec 2015 12:15:52 +0000
Subject: Re: [PATCH] elf/get-dynamic-info.h: fix early GNU_HASH processing on ia64
Authentication-results: sourceware.org; auth=none
References: <1451158325-4790-1-git-send-email-slyich at gmail dot com> <20151228051238 dot GC25803 at vapier dot lan> <5681238C dot 1010908 at redhat dot com>

On Mon, 28 Dec 2015 12:57:00 +0100
Florian Weimer <fweimer@redhat.com> wrote:

> On 12/28/2015 06:12 AM, Mike Frysinger wrote:
> > i don't think this change is what we want -- you're modifying common code
> > in a non-obvious way to trick gcc on a specific arch to generate "better"
> > code.  future versions of gcc (or reasonable code shuffling here) could
> > easily break this behavior.
> 
> Agreed, this looks rather fishy.
> 
> Would it be possible to add a GCC option which inhibits it from creating
> such relocations, so that the required parts of the dynamic linker can
> be compiled with it?

I agree the patch is fragile.
I think gcc can be taught to use something like

    movl r32 = @gprel(_rtld_local#+15032385536)
    add  r32 = r32, gp

on ia64. That would (i hope) use statically resolvable
relocation and would not require .got entry.

-- 

  Sergei

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Follow-Ups:
- Re: [PATCH] elf/get-dynamic-info.h: fix early GNU_HASH processing on ia64
  - From: Sergei Trofimovich

References:
- [PATCH] elf/get-dynamic-info.h: fix early GNU_HASH processing on ia64
  - From: slyich
- Re: [PATCH] elf/get-dynamic-info.h: fix early GNU_HASH processing on ia64
  - From: Mike Frysinger
- Re: [PATCH] elf/get-dynamic-info.h: fix early GNU_HASH processing on ia64
  - From: Florian Weimer

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