From: Florian Weimer via Libc-alpha <libc-alpha@sourceware.org>
To: Carlos O'Donell via Libc-alpha <libc-alpha@sourceware.org>
Cc: Pedro Alves <palves@redhat.com>,
Conan C Huang <conhuang@cisco.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: Mon, 29 Jun 2020 10:51:06 +0200 [thread overview]
Message-ID: <87y2o61chx.fsf@oldenburg2.str.redhat.com> (raw)
In-Reply-To: <8a15bd93-e4cc-a3bc-f902-5b3e701ec4e3@redhat.com> (Carlos O'Donell via Libc-alpha's message of "Sun, 28 Jun 2020 08:34:32 -0400")
* 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
next prev parent reply other threads:[~2020-06-29 9:42 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 [this message]
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
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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