From: "H.J. Lu via Libc-alpha" <libc-alpha@sourceware.org>
To: Daniel Walker <danielwa@cisco.com>
Cc: Florian Weimer <fweimer@redhat.com>,
Carlos O'Donell via Libc-alpha <libc-alpha@sourceware.org>,
Pedro Alves <palves@redhat.com>,
Conan C Huang <conhuang@cisco.com>,
"Metzger, Markus T" <markus.t.metzger@intel.com>,
Florian Weimer <fw@deneb.enyo.de>,
Jeremy Stenglein <jstengle@cisco.com>,
xe-linux-external@cisco.com
Subject: Re: [RFC PATCH 3/3] add r_debug multiple namespaces support
Date: Tue, 27 Jul 2021 11:14:33 -0700 [thread overview]
Message-ID: <CAMe9rOqUvLEz14VS7e_DhwRNjuENuz8F2PBQSD0fh5a696EFAw@mail.gmail.com> (raw)
In-Reply-To: <20210727173958.GB1633923@zorba>
On Tue, Jul 27, 2021 at 10:40 AM Daniel Walker <danielwa@cisco.com> wrote:
>
> On Fri, Jul 23, 2021 at 04:38:33PM -0700, H.J. Lu wrote:
> > On Mon, Jun 29, 2020 at 2:49 AM Florian Weimer via Libc-alpha
> > <libc-alpha@sourceware.org> wrote:
> > >
> > > * Carlos O'Donell via Libc-alpha:
> > >
> > > >>> I'm not sure it would work to version _r_debug, since the debugger
> > > >>> is using DT_DEBUG and we only get to put one value in that
> > > >>> .dynamic entry.
> > > >>
> > > >> The symbol version is needed to avoid problems due to copy relocations
> > > >> if the symbol is referenced directly from the main program. Without
> > > >> that, the object could be truncated. It's not a debugger
> > > >> compatibility feature.
> > > >
> > > > Correct, but this violates *how* you're supposed to use _r_debug.
> > >
> > > If it is possible to link against it, we need to add the new symbol
> > > version, in my opinion.
> > >
> > > > In the dynamic case it is different. The symbol should be looked up
> > > > via DT_DEBUG only which always points to the library-local address
> > > > of the data object (and the most recent version). In effect this
> > > > bypasses the COPY relocation?
> > >
> > > How is this supposed to work if the dynamic linker does contain
> > > DT_DEBUG?
> > >
> > > I only observe DT_DEBUG in PIE binaries, but since the dynamic loader is
> > > mapped at a random address even for ET_EXEC main programs, there must be
> > > some other mechanism to locate it.
> > >
> > > Thanks,
> > > Florian
> > >
> >
> > I opened:
> >
> > https://gitlab.com/x86-psABIs/Linux-ABI/-/issues/2
> >
> > with a proposal to extend struct r_debug for libraries loaded with
> > dlmopen, I'd like to resolve it for the next releases of glibc, binutils
> > and GDB.
>
>
> I have an updated set of changes which add a new dynamic entry
> DT_DEBUG_DLMOPEN, which was recommended by Carlos. We're still testing the
> implementation. I'm open to support different implementations.
Let's work on it after glibc 2.34 is branched.
> I found while working on this project that the clang linker adds 3 proprietary new
> dynamic entries. So there is demand to make adding to the table easier.
>
> Daniel
--
H.J.
next prev parent reply other threads:[~2021-07-27 18:15 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-26 19:32 [RFC PATCH 3/3] add r_debug multiple namespaces support Daniel Walker via Libc-alpha
2020-06-26 21:05 ` Florian Weimer via Libc-alpha
2020-06-26 21:19 ` Carlos O'Donell via Libc-alpha
2020-06-26 21:24 ` Florian Weimer via Libc-alpha
2020-06-26 21:44 ` Carlos O'Donell via Libc-alpha
2020-06-27 9:34 ` Florian Weimer
2020-06-28 12:34 ` Carlos O'Donell via Libc-alpha
2020-06-29 8:51 ` Florian Weimer via Libc-alpha
2021-07-23 23:38 ` H.J. Lu via Libc-alpha
2021-07-27 17:39 ` Daniel Walker via Libc-alpha
2021-07-27 18:14 ` H.J. Lu via Libc-alpha [this message]
2021-07-28 15:15 ` H.J. Lu via Libc-alpha
2021-07-28 15:44 ` Daniel Walker via Libc-alpha
2021-07-28 17:14 ` H.J. Lu via Libc-alpha
2021-07-28 19:02 ` Daniel Walker via Libc-alpha
2021-07-28 20:04 ` H.J. Lu via Libc-alpha
2021-08-02 4:24 ` RFC: Add DT_GNU_DEBUG H.J. Lu via Libc-alpha
2021-08-02 5:22 ` Florian Weimer via Libc-alpha
2021-08-02 13:10 ` H.J. Lu via Libc-alpha
2021-08-03 16:39 ` Daniel Walker via Libc-alpha
2021-08-03 18:08 ` H.J. Lu via Libc-alpha
2021-08-03 20:04 ` Daniel Walker via Libc-alpha
2021-08-03 18:12 ` Florian Weimer via Libc-alpha
2021-08-03 18:23 ` H.J. Lu via Libc-alpha
2021-08-03 20:13 ` Florian Weimer via Libc-alpha
2021-08-03 20:21 ` H.J. Lu via Libc-alpha
2021-08-09 14:32 ` RFC: 2 choices of DT_XXX for dlmopen H.J. Lu via Libc-alpha
2021-08-09 17:16 ` Daniel Walker via Libc-alpha
2021-08-15 0:33 ` [PATCH] Extend struct r_debug to support multiple namespaces H.J. Lu via Libc-alpha
2021-08-16 16:20 ` Daniel Walker via Libc-alpha
2021-08-17 1:07 ` H.J. Lu via Libc-alpha
2020-06-27 1:21 ` [RFC PATCH 3/3] add r_debug multiple namespaces support Daniel Walker (danielwa) via Libc-alpha
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