public inbox for gnu-gabi@sourceware.org
 help / color / mirror / Atom feed
From: "H.J. Lu" <hjl.tools@gmail.com>
To: Fangrui Song <i@maskray.me>
Cc: Mark Wielaard <mark@klomp.org>, Cary Coutant <ccoutant@gmail.com>,
		"Zhang, Annita" <annita.zhang@intel.com>,
	"Liu, Hongtao" <hongtao.liu@intel.com>,
		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: <CAMe9rOrWFu9QUb_q6UjaH5Av_CMoBCaXCj1Z_chUTDqQ4YaY=g@mail.gmail.com> (raw)
In-Reply-To: <20200219182701.vrtzwhgtpelmpaub@google.com>

On Wed, Feb 19, 2020 at 10:27 AM Fangrui Song <i@maskray.me> wrote:
>
> On 2020-02-19, H.J. Lu wrote:
> >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.
>
> One way to make things follow the spirit of https://sourceware.org/ml/gnu-gabi/2018-q4/msg00036.html
>
> * Define SHT_GNU_PROPERTY
> * Set sh_type(.note.gnu.property) to SHT_GNU_PROPERTY
> * Place SHT_GNU_PROPERTY sections in a PT_GNU_PROPERTY segment
>
> The generated PT_NOTE will not include .note.gnu.property, so the scheme is compatible with old loaders (ld.so, gdb, Linux, etc).
> New loaders should interpret PT_GNU_PROPERTY, instead of PT_NOTE.
>    ( https://patchwork.kernel.org/patch/11285409/ needs no change)
>
> This way linkers can keep treating SHT_NOTE sections as opaque and apply "Rules for Linking Unrecognized Sections" (http://www.sco.com/developers/gabi/latest/ch4.sheader.html ) when combining SHT_NOTE sections. At least for lld, there will be no special rules for input SHT_NOTE sections.
>
> I will be happy to make changes to lld and LLVM binary utilities if this
> scheme reaches consensus.

It is kind of too late now.

-- 
H.J.

  reply	other threads:[~2020-02-19 19:29 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   ` Mark Wielaard
2020-01-01  0:00   ` Fangrui Song via gnu-gabi
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             ` 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 [this message]
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             ` H.J. Lu
2020-01-01  0:00     ` Zhang, Annita

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAMe9rOrWFu9QUb_q6UjaH5Av_CMoBCaXCj1Z_chUTDqQ4YaY=g@mail.gmail.com' \
    --to=hjl.tools@gmail.com \
    --cc=annita.zhang@intel.com \
    --cc=binutils@sourceware.org \
    --cc=ccoutant@gmail.com \
    --cc=gnu-gabi@sourceware.org \
    --cc=hongtao.liu@intel.com \
    --cc=i@maskray.me \
    --cc=mark@klomp.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).