From: Jacob Kroon <jacob.kroon@gmail.com>
To: Florian Weimer <fweimer@redhat.com>,
Jacob Kroon via Gcc-help <gcc-help@gcc.gnu.org>
Subject: Re: Reserving specified size of RUNPATH entry in the dynamic section during linking
Date: Sun, 28 Nov 2021 15:31:24 +0100 [thread overview]
Message-ID: <1e0cb18e-e0fd-9f20-1037-84604a090a22@gmail.com> (raw)
In-Reply-To: <87o864h5c4.fsf@oldenburg.str.redhat.com>
On 11/28/21 12:44, Florian Weimer wrote:
> * Jacob Kroon via Gcc-help:
>
>> As part of an effort to make binaries reproducible regardless of their
>> build path, I need to enforce the same size of the RUNPATH entry in the
>> dynamic section during linking, even though I don't fill it completely.
>> Is it possible to give some flag to gnu ld that allows me to set it to a
>> specific size ? Or is there a way to patch the elf file after linking,
>> so that the entry has a specified size ?
>
> Do you want to allocate specific size so that you can patch in a
> different value later?
>
Yes exactly, but see below.
> The RUNPATH strings are in the string table, so it's necessary to
> allocate space there, and be able to find it during patching.
>
> Solaris offers this mechanism:
>
> | DT_SUNW_STRPAD
> |
> | The total size, in bytes, of the unused reserved space at the end of
> | the dynamic string table. If DT_SUNW_STRPAD is not present in an
> | object, no reserved space is available.
>
> Would that help in your case as well?
>
The problem is that for two different build I pass two different
-Wl,--rpath=<path>, and they are of different length. So I'd like to
reserve a maximum size, at link-time, which becomes the same in both
builds, so that when I later remove the rpath's, the binaries become
identical.
Jacob
next prev parent reply other threads:[~2021-11-28 14:31 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-27 22:05 Jacob Kroon
2021-11-27 22:27 ` Tom Kacvinsky
2021-11-28 14:24 ` Jacob Kroon
2021-11-28 11:44 ` Florian Weimer
2021-11-28 14:31 ` Jacob Kroon [this message]
2021-11-28 15:09 ` Dan Kegel
2021-11-28 15:17 ` Florian Weimer
2021-11-28 15:54 ` Jacob Kroon
2021-11-28 17:06 ` Florian Weimer
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