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From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Wed, 19 Feb 2020 13:45:00 -0000
Message-ID: <CAMe9rOr7=hYan1h=4BmqZ9Ep8dou_E_BBg0UjXBavi6x4cTWZA@mail.gmail.com>
Subject: Re: binutils ld and new PT_GNU_PROPERTY segment
To: Mark Wielaard <mark@klomp.org>
Cc: Fangrui Song <maskray@google.com>, "Zhang, Annita" <annita.zhang@intel.com>, 	gnu-gabi <gnu-gabi@sourceware.org>, Binutils <binutils@sourceware.org>
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On Wed, Feb 19, 2020 at 5:17 AM Mark Wielaard <mark@klomp.org> wrote:
>
> On Wed, 2020-02-19 at 04:28 -0800, H.J. Lu wrote:
> > On Wed, Feb 19, 2020 at 4:02 AM Mark Wielaard <mark@klomp.org> wrote:
> > > > https://patchwork.kernel.org/patch/11285409/
> > > >
> > > > It is for both x86 and arm64.
> > >
> > > So that is not upstream in the mainline kernel? Why can't that patch
> > > use the existing PT_NOTE segment? That would make it compatible with
> > > existing binaries that don't have this PT_GNU_PROPERTY program header.
> >
> > Kernel loader is one of motivations of PT_GNU_PROPERTY.  Kernel loader
> > only wants to check PT_XXX.
>
> So they can check PT_NOTE because it provides the same information and
> is already available in existing binaries.
>

Please take a look at glibc note.gnu.property parser.  It is very complicated to
check for invalid .note.gnu.property sections generated by the older
linkers with
the new object.  Kernel loader doesn't want to do it.

-- 
H.J.