From: "H.J. Lu" <hjl.tools@gmail.com>
To: Suprateeka R Hegde <hegdesmailbox@gmail.com>
Cc: "Carlos O'Donell" <carlos@redhat.com>, gnu-gabi@sourceware.org
Subject: Re: RFC: ABI support for special memory area
Date: Sun, 01 Jan 2017 00:00:00 -0000 [thread overview]
Message-ID: <CAMe9rOqt-9GCH=XdhBpwT0xK_Csu3PSYKAheCn-BnpCXamCjNQ@mail.gmail.com> (raw)
In-Reply-To: <96294553-8088-0a9a-3957-1006743619d5@gmail.com>
On Thu, Mar 30, 2017 at 9:02 AM, Suprateeka R Hegde
<hegdesmailbox@gmail.com> wrote:
> On 03/27/17 21:45, H.J. Lu wrote:
>>
>> There is a way to support GNU_MBIND segments without the glibc changes.
>> Instead, dl_iterate_phdr
>>
>> int dl_iterate_phdr (int (*callback) (struct dl_phdr_info *info,
>> size_t size, void *data),
>> void *data);
>>
>> is called via the .init_array section to process GNU_MBIND segments in
>> executable and shared objects:
>>
>> static int
>> callback (struct dl_phdr_info *info, size_t size, void *data)
>> {
>> Compute the load address of the current module.
>> if info->dlpi_addr == the load address of the current module
>> {
>> check ELF program headers and process GNU_MBIND segments
>> return 1;
>> }
>>
>> return 0;
>> }
>>
>> static void
>> call_gnu_mbind_setup (void)
>> {
>> dl_iterate_phdr (callback, NULL);
>> }
>>
>> static void (*init_array) (void)
>> __attribute__ ((section (".init_array"), used))
>> = &call_gnu_mbind_setup;
>
> This looks very ideal and perfect and matches my requirement too. Are
> you suggesting this dl_iterate_phdr(3) as the way in your proposal
> instead of the __gnu_mbind_setup?
Yes.
> Or are you suggesting that for all the implementations that need
> different arguments (like that of my NVM) compared to
> __gnu_mbind_setup_v1, we go with this dl_iterate_phdr(3) way?
__gnu_mbind_setup_v1 is removed so that it will work with
existing C libraries with dl_iterate_phdr.
> I am OK either way.
>
> However, I am just thinking that your earlier approach --
> __gnu_mbind_setup -- is better when shared libraries with GNU_MBIND
> segments are dlopen'ed. They dont have to iterate all over again to
> reach their PHDR. Or what is the recommendation for such dlopen'ed
> libraries?
It is true that dl_iterate_phdr is called by every shared object, dlopened or
not, to locate its own PHDR.
> And this dl_iterate_phdr(3) not being part of any standards, may change
> in a totally incompatible way in the future.
>
dl_iterate_phdr isn't in any standard. But it is in glibc. Given that my
proposal is a GNU extension, it isn't a major issue. Working with
existing glibc is a big plus.
--
H.J.
next prev parent reply other threads:[~2017-03-30 16:40 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-01 0:00 H.J. Lu
2017-01-01 0:00 ` Carlos O'Donell
2017-01-01 0:00 ` H.J. Lu
2017-01-01 0:00 ` Carlos O'Donell
2017-01-01 0:00 ` H.J. Lu
2017-01-01 0:00 ` Florian Weimer
2017-01-01 0:00 ` H.J. Lu
2017-01-01 0:00 ` Suprateeka R Hegde
2017-01-01 0:00 ` H.J. Lu
2017-01-01 0:00 ` Suprateeka R Hegde
2017-01-01 0:00 ` H.J. Lu
2017-01-01 0:00 ` Carlos O'Donell
2017-01-01 0:00 ` Suprateeka R Hegde
2017-01-01 0:00 ` H.J. Lu
2017-01-01 0:00 ` Suprateeka R Hegde
2017-01-01 0:00 ` H.J. Lu
2017-01-01 0:00 ` H.J. Lu
2017-01-01 0:00 ` Suprateeka R Hegde
2017-01-01 0:00 ` H.J. Lu
2017-01-01 0:00 ` Suprateeka R Hegde
2017-01-01 0:00 ` H.J. Lu
2017-01-01 0:00 ` Suprateeka R Hegde
2017-01-01 0:00 ` H.J. Lu
2017-01-01 0:00 ` Suprateeka R Hegde
2017-01-01 0:00 ` H.J. Lu [this message]
2017-01-01 0:00 ` Suprateeka R Hegde
2017-01-01 0:00 ` H.J. Lu
2017-01-01 0:00 ` Florian Weimer
2017-01-01 0:00 ` H.J. Lu
2017-01-01 0:00 ` Florian Weimer
2017-01-01 0:00 ` H.J. Lu
2017-01-01 0:00 ` Florian Weimer
2017-01-01 0:00 ` H.J. Lu
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