From: "H.J. Lu" <hjl.tools@gmail.com>
To: Joseph Myers <joseph@codesourcery.com>
Cc: GNU C Library <libc-alpha@sourceware.org>
Subject: Re: [PATCH 3/7] Add GLIBC_ABI_DT_RELR for DT_RELR support
Date: Fri, 4 Feb 2022 12:04:11 -0800 [thread overview]
Message-ID: <CAMe9rOqmyxeRVwFcXyondcjSzMvG8_9AMeH0B_FY1SiX1HjKcg@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.22.394.2202041950570.244210@digraph.polyomino.org.uk>
On Fri, Feb 4, 2022 at 11:53 AM Joseph Myers <joseph@codesourcery.com> wrote:
>
> On Thu, 3 Feb 2022, H.J. Lu via Libc-alpha wrote:
>
> > +%if HAVE_DT_RELR
> > + GLIBC_ABI_DT_RELR {
> > + # This symbol is used only for empty version map and will be removed
> > + # by scripts/versions.awk.
> > + __placeholder_only_for_empty_version_map;
> > + }
>
> My understanding is that HAVE_DT_RELR describes a property of the linker
> used to build glibc, not a property of what features glibc itself
> supports.
>
> The symbol versions provided by glibc, and whether glibc supports binaries
> using RELR relocations, should be independent of whether the linker
> version used to build glibc supports such relocations. A given glibc
> version should either always support RELR relocations (for a given glibc
> ABI) or never support them (for that ABI), independent of linker features,
> and likewise the symbol versions provided by glibc should be independent
> of linker features.
>
In my cover letter, I said
Binutils 2.38 supports DT_RELR on x86 with the -z report-relative-reloc
option. When DT_RELR is enabled, ld adds a GLIBC_ABI_DT_RELR symbol
version dependency on libc.so to outputs. The DT_RELR support is enabled
in ld.so only if the linker supports -z report-relative-reloc option.
and the first patch has
# define ELF_DYNAMIC_RELOCATE(map, scope, lazy, consider_profile, skip_ifunc) \
do { \
int edr_lazy = elf_machine_runtime_setup ((map), (scope), (lazy), \
(consider_profile)); \
ELF_DYNAMIC_DO_REL ((map), (scope), edr_lazy, skip_ifunc); \
ELF_DYNAMIC_DO_RELA ((map), (scope), edr_lazy, skip_ifunc);
\
+ if (HAVE_DT_RELR && ((map) != &GL(dl_rtld_map) || DO_RTLD_BOOTSTRAP)) \
+ ELF_DYNAMIC_DO_RELR (map); \
} while (0)
If HAVE_DT_RELR is 0, DT_RELR is disabled.
--
H.J.
next prev parent reply other threads:[~2022-02-04 20:04 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-03 18:09 [PATCH 0/7] Support DT_RELR relative relocation format H.J. Lu
2022-02-03 18:09 ` [PATCH 1/7] elf: Support DT_RELR relative relocation format [BZ #27924] H.J. Lu
2022-02-03 18:09 ` [PATCH 2/7] elf: Properly handle zero DT_RELA/DT_REL values H.J. Lu
2022-02-03 18:09 ` [PATCH 3/7] Add GLIBC_ABI_DT_RELR for DT_RELR support H.J. Lu
2022-02-04 19:53 ` Joseph Myers
2022-02-04 20:04 ` H.J. Lu [this message]
2022-02-04 20:10 ` Joseph Myers
2022-02-04 20:40 ` H.J. Lu
2022-02-04 21:01 ` Joseph Myers
2022-02-04 21:08 ` H.J. Lu
2022-02-04 23:58 ` Joseph Myers
2022-02-05 17:24 ` H.J. Lu
2022-02-03 18:09 ` [PATCH 4/7] x86/configure.ac: Define PI_STATIC_AND_HIDDEN/SUPPORT_STATIC_PIE H.J. Lu
2022-02-03 18:09 ` [PATCH 5/7] x86: Define SUPPORT_DT_RELR H.J. Lu
2022-02-03 18:09 ` [PATCH 6/7] Add --disable-default-dt-relr H.J. Lu
2022-02-03 18:09 ` [PATCH 7/7] NEWS: Mention DT_RELR support H.J. Lu
2022-02-04 20:00 ` [PATCH 0/7] Support DT_RELR relative relocation format Joseph Myers
2022-02-04 20:08 ` H.J. Lu
2022-02-04 20:12 ` Joseph Myers
2022-02-04 20:32 ` Fangrui Song
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