From: Kaylee Blake <klkblake@gmail.com>
To: binutils@sourceware.org
Subject: Re: RFC: [PATCH] ELF: Don't require section header on ELF objects
Date: Tue, 10 Mar 2020 00:24:51 +1030 [thread overview]
Message-ID: <871cf36a-5690-a8a7-68af-2cf0f54c5b5d@gmail.com> (raw)
In-Reply-To: <20200309134427.GO5384@bubble.grove.modra.org>
On 10/3/20 12:14 am, Alan Modra wrote:
> On Mon, Mar 09, 2020 at 11:24:44PM +1030, Kaylee Blake wrote:
>> On 9/3/20 6:43 pm, Florian Weimer wrote:
>>> In my opinion, it should NOT be possible to link against objects
>>> without section headers. Lack of section headers clearly marks the
>>> object as a run-time only object. This is useful if you want to
>>> prevent developers to create DT_NEEDED dependencies on internal
>>> libraries, for example.
>
> I agree.
>
>> For shared objects without debug symbols, the section header table is
>> ~2kB on average of redundant data. I'm also not a fan of the
>> inconsistency of having shared libraries that the dynamic linker is
>> perfectly happy to load, but ld can't link against, especially since
>> this seems like an oversight rather than an intended design decision.
>
> The ELF spec designed things that way. See figure 4.1 which I'll try
> to represent in text.
>
> Figure 4-1: Object File Format
>
> |----------------------| |----------------------|
> | ELF Header | | ELF Header |
> |----------------------| |----------------------|
> | Program header table | | Program header table |
> | optional | | required |
> |----------------------| |----------------------|
> | Section 1 | | Segment 1 |
> |----------------------| |----------------------|
> | ... | | Segment 2 |
> |----------------------| |----------------------|
> | Section n | | Segment 3 |
> |----------------------| |----------------------|
> | ... | | ... |
> |----------------------| |----------------------|
> | Section header table | | Section header table |
> | required | | optional |
> |----------------------| |----------------------|
> Linking View Execution View
>
I had interpreted that table in combination to various other references
to which things are required vs optional in shared objects as meaning
that the "execution view" applied to executables and shared objects, and
the "linking view" applied to relocatable objects. You're saying that
that table should be interpreted as saying that if a shared object is to
be linkable, the spec is requiring it to have both sets of headers?
--
Kaylee Blake <klkblake@gmail.com>
C is the worst language, except for all the others.
next prev parent reply other threads:[~2020-03-09 13:54 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-08 17:59 H.J. Lu
2020-03-08 18:06 ` H.J. Lu
2020-03-08 23:35 ` Alan Modra
2020-03-08 23:46 ` H.J. Lu
2020-03-09 0:02 ` H.J. Lu
2020-03-09 0:02 ` Kaylee Blake
2020-03-09 0:05 ` Alan Modra
2020-03-09 1:36 ` H.J. Lu
2020-03-09 1:59 ` Kaylee Blake
2020-03-09 2:23 ` Alan Modra
2020-03-09 2:35 ` H.J. Lu
2020-03-09 4:14 ` H.J. Lu
2020-03-09 4:59 ` Kaylee Blake
2020-03-09 11:56 ` Alan Modra
2020-03-08 23:24 ` Kaylee Blake
2020-03-08 23:29 ` H.J. Lu
2020-03-08 23:38 ` Alan Modra
2020-03-08 23:45 ` H.J. Lu
2020-03-12 2:14 ` Fangrui Song
2020-03-09 8:13 ` Florian Weimer
2020-03-09 12:54 ` Kaylee Blake
2020-03-09 13:06 ` Florian Weimer
2020-03-09 13:14 ` Kaylee Blake
2020-03-09 13:16 ` Florian Weimer
2020-03-09 13:28 ` Kaylee Blake
2020-03-09 13:29 ` Florian Weimer
2020-03-09 13:45 ` Kaylee Blake
2020-03-09 13:54 ` H.J. Lu
2020-03-09 14:02 ` Kaylee Blake
2020-03-09 14:52 ` Florian Weimer
2020-03-09 15:07 ` Kaylee Blake
2020-03-09 15:29 ` Florian Weimer
2020-03-09 13:44 ` Alan Modra
2020-03-09 13:54 ` Kaylee Blake [this message]
2020-03-09 22:34 ` Alan Modra
2020-03-10 0:14 ` H.J. Lu
2020-03-09 14:34 ` Michael Matz
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