From: "H.J. Lu" <hjl.tools@gmail.com>
To: Fangrui Song <maskray@google.com>
Cc: GNU C Library <libc-alpha@sourceware.org>,
Binutils <binutils@sourceware.org>
Subject: Re: [PATCH] elf: Support DT_RELR relative relocation format [BZ #27924]
Date: Fri, 8 Oct 2021 09:51:41 -0700 [thread overview]
Message-ID: <CAMe9rOpR+AevfRHEpu=iXcfQxsLQus6Cu25viR58D-utD=v5ng@mail.gmail.com> (raw)
In-Reply-To: <20211008065740.1485737-1-maskray@google.com>
On Thu, Oct 7, 2021 at 11:58 PM Fangrui Song via Binutils
<binutils@sourceware.org> wrote:
>
> PIC objects (especially PIE and symbolic shared objects) usually have many
> relative relocations. In 2017/2018, SHT_RELR/DT_RELR was proposed on
> https://groups.google.com/g/generic-abi/c/bX460iggiKg/m/GxjM0L-PBAAJ
> ("Proposal for a new section type SHT_RELR") and welcomed by many parties
> (including Solaris). This packed format can typically save 95% dynamic
> relocation section size for PIE. The vaddr size of a PIE can be 10% smaller.
>
> * Chrome OS folks have carried a local patch for a while (latest version:
> https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/refs/heads/main/sys-libs/glibc/files/local/glibc-2.32).
> I.e. this feature has been battle tested.
> * Android bionic supports DT_RELR.
> * The Linux kernel has supported CONFIG_RELR since 2019-08
> (https://git.kernel.org/linus/5cf896fb6be3effd9aea455b22213e27be8bdb1d).
> * A musl patch (by me) exists but is not applied:
> https://www.openwall.com/lists/musl/2019/03/06/3
>
> I believe upstream glibc should support DT_RELR to benefit all Linux
> distributions.
>
> As of linker support (to the best of my knowledge):
>
> * LLD support DT_RELR.
> * https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/refs/heads/main/sys-devel/binutils/files/
> has a gold patch.
> * GNU ld feature request https://sourceware.org/bugzilla/show_bug.cgi?id=27923
>
> I wish that GNU ld and gold maintainers can implement the feature as well :)
This feature should be implemented in GNU linker first before getting
into glibc.
H.J.
next prev parent reply other threads:[~2021-10-08 16:52 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-08 6:57 Fangrui Song
2021-10-08 15:39 ` Florian Weimer
2021-10-08 16:36 ` Fangrui Song
2021-10-08 19:41 ` Cary Coutant
2021-10-08 16:51 ` H.J. Lu [this message]
2021-10-08 17:37 ` Fangrui Song
2021-10-08 17:43 ` H.J. Lu
2021-10-08 18:46 ` Fangrui Song
2021-10-11 7:48 ` Jan Beulich
2021-10-11 18:43 ` Fāng-ruì Sòng
2021-10-11 22:08 ` Joseph Myers
2021-10-12 8:14 ` Jan Beulich
2021-10-12 8:18 ` Jan Beulich
2021-10-12 14:09 ` H.J. Lu
2021-10-12 16:07 ` Fāng-ruì Sòng
2021-10-13 6:00 ` Jan Beulich
2021-10-13 6:13 ` Fāng-ruì Sòng
2021-10-13 6:18 ` Fāng-ruì Sòng
2021-10-18 7:59 ` Jan Beulich
2021-10-16 20:22 ` Fangrui Song
2021-10-26 23:28 ` Cary Coutant
2021-10-11 21:47 ` Joseph Myers
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