Re: [PATCH 0/7] Support DT_RELR relative relocation format

["H.J. Lu" <hjl.tools@gmail.com>]

On Fri, Feb 4, 2022 at 12:00 PM Joseph Myers <joseph@codesourcery.com> wrote:
>
> On Thu, 3 Feb 2022, H.J. Lu via Libc-alpha wrote:
>
> > DT_RELR is enabled in glibc shared libraries and position independent
> > executables (PIE) automatically if linker supports -z pack-relative-relocs
> > nd the architecture defines SUPPORT_DT_RELR in config.h.  At the moment,
> > only x86 targets define SUPPORT_DT_RELR.
>
> The patch 1 description says "This patch is simpler than Chrome OS's glibc
> patch and makes ELF_DYNAMIC_DO_RELR available to all ports.".
>
> What exactly would other architectures need to add in glibc to provide
> RELR support, since I don't see any actual architecture-specific code in

DT_RELR is enabled only if linker supports -z report-relative-reloc option
which adds GLIBC_ABI_DT_RELR dependency in the linker output to
prevent random crashes with the older glibc binaries.

> this patch series outside of configure scripts?  Please provide text you
> would propose to add to https://sourceware.org/glibc/wiki/PortStatus that
> gives an architecture maintainer all the information needed to add such
> support for their architecture.  If in fact no architecture-specific code
> should be needed, please remove the SUPPORT_DT_RELR handling and just
> allow glibc to support the feature for all architectures (while using RELR
> in glibc itself for architectures where the linker support is present, as
> detected by a configure test on the linker rather than hardcoding
> information about which architectures have that linker support at a given
> time).
>
> The default should be to support a feature for all architectures.  A patch
> series supporting a feature for only some architectures needs a positive
> reason for excluding other architectures (for example, that each
> architecture needs architecture-specific code, for which you provide
> suitable documentation to add to PortStatus to help architecture
> maintainers in writing such code).
>
> --
> Joseph S. Myers
> joseph@codesourcery.com



-- 
H.J.