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From: Mark Wielaard <mark@klomp.org>
To: Fangrui Song <maskray@google.com>,
	"H.J. Lu" <hjl.tools@gmail.com>,
		"Zhang, Annita" <annita.zhang@intel.com>
Cc: gnu-gabi <gnu-gabi@sourceware.org>, Binutils <binutils@sourceware.org>
Subject: Re: binutils ld and new PT_GNU_PROPERTY segment
Date: Wed, 01 Jan 2020 00:00:00 -0000	[thread overview]
Message-ID: <dadc7c7f28171eae1fe537d0be4fa4fbdaf4eaab.camel@klomp.org> (raw)
In-Reply-To: <20200219023120.gvr4ajolbjbqcfix@google.com>

Hi,

On Tue, 2020-02-18 at 18:31 -0800, Fangrui Song wrote:
>  From what I can see, neither the Linux kernel nor glibc uses
> PT_GNU_PROPERTY.
> glibc/sysdeps/x86/dl-prop.h parses PT_NOTE.

That is my impression too.

> I tend to agree with Cary
> (https://sourceware.org/ml/gnu-gabi/2018-q4/msg00036.html) that
> .note.gnu.property should have been designed as a different section
> type
> because its combining semantics are different from other notes
> (we could apply "Rules for Linking Unrecognized Sections" to all
> SHT_NOTE sections) but it is too late to change the section type.

Agreed.

> A separate segment type (PT_GNU_PROPERTY) looks fine to me.
> glibc should probably be updated to parse PT_GNU_PROPERTY instead.

I think it is confusing to now introduce a new segment type which
basically provides the same information as the PT_NOTE segement. It is
ill defined because it needs to be matched to a magic section name.
Which makes things harder for tools dealing with generic SHT_NOTE
sections (they would have to preserve the magic section name, might not
be able to merge notes, etc.)

> (Recently I read some ABI decisions and I noticed that I frequently see
> the term "it is too late". As a contributor of both lld and LLVM binary
> utilities (and the implementer of a bunch of GNU_PROPERTY changes), I
> hope that the LLVM community can be informed of such changes earlier.  A
> lot of people are not subscribed to any of the mailing lists (recently I
> visit the archives from time to time).

Yeah, we really need to do a better job coordinating and communicating.
Even though I am trying to keep up with these lists I am often
surprised by changes like this which seem to have just been added to
binutils without trying to get consensus with other GNU/ELF tool
implementations about the precise semantics or whether a feature is
simply redundant with existing practice.

Cheers,

Mark

  reply	other threads:[~2020-02-19 10:58 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-01  0:00 Mark Wielaard
2020-01-01  0:00 ` H.J. Lu
2020-01-01  0:00   ` Fangrui Song via gnu-gabi
2020-01-01  0:00     ` Mark Wielaard [this message]
2020-01-01  0:00       ` H.J. Lu
2020-01-01  0:00         ` Mark Wielaard
2020-01-01  0:00           ` H.J. Lu
2020-01-01  0:00             ` H.J. Lu
2020-01-01  0:00             ` Mark Wielaard
2020-01-01  0:00               ` H.J. Lu
2020-01-01  0:00                 ` Fangrui Song
2020-01-01  0:00                   ` H.J. Lu
2020-01-01  0:00                     ` Mark Wielaard
2020-01-01  0:00                       ` H.J. Lu
2020-01-01  0:00                         ` Mark Wielaard
2020-01-01  0:00                           ` H.J. Lu
2020-01-01  0:00                             ` Fangrui Song
2020-01-01  0:00                               ` H.J. Lu
2020-01-01  0:00                             ` Mark Wielaard
2020-01-01  0:00                               ` Fangrui Song
2020-04-01  8:46                                 ` Florian Weimer
2020-04-01  9:22                                   ` Szabolcs Nagy
2020-04-01  9:29                                     ` Florian Weimer
2020-04-01 10:10                                       ` Szabolcs Nagy
2020-04-01 10:21                                         ` Florian Weimer
2020-01-01  0:00     ` Zhang, Annita
2020-01-01  0:00   ` Mark Wielaard

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