From: "H.J. Lu" <hjl.tools@gmail.com>
To: Florian Weimer <fweimer@redhat.com>
Cc: Mark Wielaard <mark@klomp.org>,
x86-64-abi <x86-64-abi@googlegroups.com>,
Binutils <binutils@sourceware.org>,
GNU C Library <libc-alpha@sourceware.org>
Subject: Re: PT_NOTE alignment, NT_GNU_PROPERTY_TYPE_0, glibc and gold
Date: Fri, 17 Aug 2018 08:13:22 -0700 [thread overview]
Message-ID: <CAMe9rOqd8geYN0=yeqW++tYhMC8VCuPp35M1NGS5twHm0RE+XQ@mail.gmail.com> (raw)
In-Reply-To: <fc9da975-92ab-6597-b0ff-2653963f0869@redhat.com>
On Thu, Aug 16, 2018 at 11:20 PM, Florian Weimer <fweimer@redhat.com> wrote:
> On 08/16/2018 09:16 PM, Mark Wielaard wrote:
>>
>> On Thu, Aug 16, 2018 at 04:21:05PM +0200, Florian Weimer wrote:
>>>
>>> On 08/16/2018 03:39 PM, H.J. Lu wrote:
>>>>
>>>> glibc only discards 4-byte aligned NT_GNU_PROPERTY_TYPE_0 note
>>>> since NT_GNU_PROPERTY_TYPE_0 note follows gABI. If gold
>>>> generates 4 byte alignment, it is a gold bug.
>>>
>>>
>>> I filed: https://sourceware.org/bugzilla/show_bug.cgi?id=23535
>>
>>
>> I don't think this is a bug in gold, but one in ld:
>> https://sourceware.org/bugzilla/show_bug.cgi?id=22749
>>
>> In the GNU abi all ELF Notes are arrays of 32bit words
>> (and so 4-byte aligned). This is the same for most other
>> ELF systems. Making the ELF Notes fields 64bit words (and
>> so 8-byte aligned) in ELFCLASS64 would indeed be what gabi
>> literally says, but not what GNU systems, and others, follow.
>
>
> The binaries are already out there and will be around for a while, even if
> we reduce the alignment now. So generic ELF parsers need to cope with these
> binaries anyway.
>
>> Having a mix of 4-byte words and 8-byte words ELF Notes
>> in the same ELF file seems unnecessarily confusing and
>> introduces extra segments and sections.
>
>
> There are no 8-byte word ELF notes on GNU systems, that's an HP-UX feature.
> The new 8-byte-aligned notes still have a four-byte header.
>
> But like you, I don't yet see the value of the 8-byte alignment. We could
> decide that the current gold behavior is valid, fix glibc, and move on.
Gold didn't follow the spec and should be fixed.
--
H.J.
next prev parent reply other threads:[~2018-08-17 15:13 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAMe9rOrrayKnc_cPm4SmnDnUGLbBUmOYMBTMOM8KLAHVmb=rUQ@mail.gmail.com>
2018-08-16 13:00 ` PT_NOTE alignment, NT_GNU_PROPERTY_TYPE_0, glibc and gold (was: Re: [PATCH] Document GNU_PROPERTY_X86_ISA_1_[USED|NEEDED]) Florian Weimer
2018-08-16 13:19 ` H.J. Lu
2018-08-16 13:29 ` H.J. Lu
2018-08-16 13:31 ` PT_NOTE alignment, NT_GNU_PROPERTY_TYPE_0, glibc and gold Florian Weimer
2018-08-16 13:39 ` H.J. Lu
2018-08-16 14:01 ` Florian Weimer
2018-08-16 14:43 ` H.J. Lu
2018-08-16 14:21 ` Florian Weimer
2018-08-16 17:46 ` H.J. Lu
2018-08-16 19:16 ` Mark Wielaard
2018-08-16 19:36 ` H.J. Lu
2018-08-17 6:04 ` Mark Wielaard
2018-08-17 6:20 ` Florian Weimer
2018-08-17 6:41 ` Mark Wielaard
2018-08-17 15:10 ` H.J. Lu
2018-08-17 21:05 ` Mark Wielaard
2018-08-21 23:02 ` Cary Coutant
2018-08-22 9:39 ` Florian Weimer
2018-08-22 10:08 ` Mark Wielaard
2018-08-22 23:36 ` Cary Coutant
2018-08-24 18:39 ` Florian Weimer
2018-08-23 14:41 ` Michael Matz
2018-08-23 14:43 ` Florian Weimer
2018-08-17 15:13 ` H.J. Lu [this message]
2018-09-19 19:22 ` Florian Weimer
2018-09-21 12:55 ` Michael Matz
2018-09-21 13:04 ` Florian Weimer
2018-09-26 17:39 ` Cary Coutant
2018-09-26 18:36 ` H.J. Lu
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