From: "H.J. Lu" <hjl.tools@gmail.com>
To: Cary Coutant <ccoutant@gmail.com>
Cc: "Carlos O'Donell" <carlos@redhat.com>,
Florian Weimer <fweimer@redhat.com>,
Szabolcs Nagy <nsz@port70.net>, Jan Beulich <JBeulich@suse.com>,
Rich Felker <dalias@libc.org>,
Binutils <binutils@sourceware.org>,
gnu-gabi@sourceware.org
Subject: Re: RFC: Add SHT_GNU_PHDRS
Date: Mon, 01 Jan 2018 00:00:00 -0000 [thread overview]
Message-ID: <CAMe9rOpqH6E1-c8bYE5R-x5aErey8ornx9eWp9eDdpuQhS9zow@mail.gmail.com> (raw)
In-Reply-To: <CAJimCsG0SSDPHhHapZfK97CU45AQsXgkdH02mHcM1H1S9ic8ug@mail.gmail.com>
On Thu, Sep 27, 2018 at 3:34 PM, Cary Coutant <ccoutant@gmail.com> wrote:
>> > I'm now under the impression that the bits that are PT_LOAD'ed all need
>> > to be covered by (allocated) sections. A zero-sized section doesn't
>> > cover anything, so it doesn't address this requirement of the ELF
>> > specification.
>>
>> I agree. What we did in the past by relying on phdrs to be accidentally
>> in the first PT_LOAD segment always irked me as bad design.
>>
>> If we need access to program header we need clear semantics for doing so,
>> not hackish kludges to force the linker to get it onto a page that also
>> happened to be mapped. This is just poor engineering on our part.
>
> It seems to me that the kernel loader should make the program headers
> available to the dynamic loader through the aux vector, whether
> they're part of a PT_LOAD segment or not. That should be part of the
> psABI. The gABI clearly requires that the dynamic loader has access to
> the program headers (e.g., it needs to find PT_DYNAMIC), but it
> doesn't care how the implementation accomplishes that.
>
Dynamic loader has no problem. The problem is kernel passes
AT_PHDR to main, which points to the unmmaped address. We can
ask for kernel change or make kernel happy.
My current .note.gnu.property patch only works for x86. We can
add
#define GNU_PROPERTY_PHDRS 3
so that it can be used for all targets.
--
H.J.
next prev parent reply other threads:[~2018-09-28 13:43 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-01 0:00 H.J. Lu
[not found] ` <CAORpzuOWtHeqBLEE+MMN4-TZyp6Z1r-MdmyNv7Zj-BhxMstr=g@mail.gmail.com>
2018-01-01 0:00 ` H.J. Lu
2018-01-01 0:00 ` Florian Weimer
2018-01-01 0:00 ` Jan Beulich
2018-01-01 0:00 ` Florian Weimer
2018-01-01 0:00 ` Szabolcs Nagy
2018-01-01 0:00 ` H.J. Lu
2018-01-01 0:00 ` Florian Weimer
2018-01-01 0:00 ` H.J. Lu
2018-01-01 0:00 ` Florian Weimer
2018-01-01 0:00 ` Michael Matz
2018-01-01 0:00 ` Florian Weimer
2018-01-01 0:00 ` Michael Matz
2018-01-01 0:00 ` Carlos O'Donell
2018-01-01 0:00 ` Cary Coutant
2018-01-01 0:00 ` H.J. Lu [this message]
2018-01-01 0:00 ` Rich Felker
2018-01-01 0:00 ` H.J. Lu
2018-01-01 0:00 ` Carlos O'Donell
2018-01-01 0:00 ` H.J. Lu
2018-01-01 0:00 ` Carlos O'Donell
2018-01-01 0:00 ` Florian Weimer
2018-01-01 0:00 ` Cary Coutant
2018-01-01 0:00 ` Carlos O'Donell
2018-01-01 0:00 ` H.J. Lu
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