From: "H.J. Lu" <hjl.tools@gmail.com>
To: Mark Wielaard <mark@klomp.org>
Cc: Generic System V Application Binary Interface
<generic-abi@googlegroups.com>,
Suprateeka R Hegde <hegdesmailbox@gmail.com>,
Cary Coutant <ccoutant@gmail.com>,
Mark Mentovai <mark@chromium.org>,
gnu-gabi@sourceware.org
Subject: Re: What integer type should ELF note header have?
Date: Sun, 01 Jan 2017 00:00:00 -0000 [thread overview]
Message-ID: <CAMe9rOoMVmtuMX_3+anbz6hZcW_PusNi4VeszkKgBKcQ9Yv3kA@mail.gmail.com> (raw)
In-Reply-To: <1513245995.15696.78.camel@klomp.org>
On Thu, Dec 14, 2017 at 2:06 AM, Mark Wielaard <mark@klomp.org> wrote:
> On Wed, 2017-12-13 at 10:09 -0800, H.J. Lu wrote:
>> On Wed, Dec 13, 2017 at 5:57 AM, Mark Wielaard <mark@klomp.org>
>> wrote:
>> > On Mon, 2017-12-11 at 04:11 -0800, H.J. Lu wrote:
>> > > Note segments/sections with 8 byte alignment should use Elf64_Nhdr64.
>> > > If we want to do it, we should do it now before
>> > > NT_GNU_PROPERTY_TYPE_0
>> > > notes with the existing Elf64_Nhdr are generated by GCC 8 with
>> > > -fcf-protection -mcet.
>> >
>> > Yes, I think having a new note type is the way to go, if we want to
>> > change the alignment requirements.
>> >
>> > BTW. What is the reason you need 8 byte aligned notes?
>>
>> NT_GNU_PROPERTY_TYPE_0 can have 64-bit integer properties
>> in 64-bit objects. They should be aligned to 8 bytes.
>
> Not necessarily. You can have not naturally aligned data in files. ELF
> files are cross architectures, so you have to account for different
64-bit integers in NT_GNU_PROPERTY_TYPE_0 note are naturally aligned
by design so that int64 can be used to access 64-bit integers in
NT_GNU_PROPERTY_TYPE_0 note on all architectures.
> alignments and endian issues anyway. Is there a specific property of
> these 64-bit integers that require them to be 8 byte aligned in the
> note descriptor data?
Currently it has GNU_PROPERTY_STACK_SIZE as 64-bit integer
in 64-bit objects. We may add more in the future.
--
H.J.
next prev parent reply other threads:[~2017-12-14 16:39 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAMe9rOoV5u263JotP=XpiYEzcnjCJOG3U-0X5bnK-WwZoOKTQA@mail.gmail.com>
[not found] ` <99c8440b-54d8-41bc-6e4d-cd1894536bb7@Oracle.COM>
[not found] ` <CAJimCsHE8cMY8MY=BYyQ+o4b14LtQKa2u+SiXWi1o4zBQB9t9Q@mail.gmail.com>
2017-01-01 0:00 ` Suprateeka R Hegde
2017-01-01 0:00 ` Ali Bahrami
2017-01-01 0:00 ` Ali Bahrami
2017-01-01 0:00 ` Mark Wielaard
2017-01-01 0:00 ` H.J. Lu
2017-01-01 0:00 ` Mark Wielaard
2017-01-01 0:00 ` H.J. Lu
2017-01-01 0:00 ` Mark Wielaard
[not found] ` <3704867e-58b8-3da1-2b29-959ad67a540d@Oracle.COM>
[not found] ` <1513355861.15696.95.camel@klomp.org>
[not found] ` <CAMe9rOrAFX5gPCB355A=vP0VpWQT1x8V3Hrttxm5ZRsvG1FXXw@mail.gmail.com>
2017-01-01 0:00 ` Mark Wielaard
[not found] ` <CAMe9rOosYw=9kF8eTUnxwQXNguvCrcK5GSaM=vbUUSA6+J49Zw@mail.gmail.com>
2017-01-01 0:00 ` Mark Wielaard
2017-01-01 0:00 ` H.J. Lu [this message]
2017-01-01 0:00 ` Mark Wielaard
2017-01-01 0:00 ` H.J. Lu
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