From: Fangrui Song <maskray@google.com>
To: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
Cc: "H.J. Lu" <hjl.tools@gmail.com>,
Florian Weimer <fweimer@redhat.com>,
Wilco Dijkstra via Libc-alpha <libc-alpha@sourceware.org>
Subject: Re: [RESEND PATCH] Makeconfig: Set pie-ccflag to -fPIE by default
Date: Mon, 29 Aug 2022 12:57:03 -0700 [thread overview]
Message-ID: <20220829195703.tvrqhe7ggnaks3oo@google.com> (raw)
In-Reply-To: <CAMe9rOrwTuucuMEKrTizYSJ92B5JBf7n7rTNhgOWcLPUhKvCYA@mail.gmail.com>
On 2022-08-29, H.J. Lu via Libc-alpha wrote:
>On Mon, Aug 29, 2022 at 8:27 AM Wilco Dijkstra <Wilco.Dijkstra@arm.com> wrote:
>>
>> Hi Florian,
>>
>> * Wilco Dijkstra via Libc-alpha:
>> >> However this leads to the question is why aren't all symbols marked as
>> >> hidden in the static PIE build? Ie. are there any symbols that must be
>> >> shared with a DSO loaded by a dl_open?
>> >
>> > The static main executable does not have a dynamic symbol table, so such
>> > sharing cannot happen (except through function pointers being passed
>> > around, but symbol visibility of course does not matter there).
>>
>> Right, so it should be safe then to mark all symbols as hidden.
>>
>> We could also teach GCC to never emit GOT indirections with -fPIE -static
>> (the only reason to use a GOT indirection is to avoid copy relocations in
>> dynamically linked binaries).
>>
>
>But -static isn't passed to cc1.
With Clang, -fPIE -fno-direct-access-external-data can be used.
See https://maskray.me/blog/2021-01-09-copy-relocations-canonical-plt-entries-and-protected
GCC's x86 port went with -mdirect-extern-access.
next prev parent reply other threads:[~2022-08-29 19:57 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-26 18:39 Wilco Dijkstra
2022-08-26 19:02 ` H.J. Lu
2022-08-26 19:45 ` Richard Henderson
2022-08-26 20:11 ` H.J. Lu
2022-08-29 11:49 ` Wilco Dijkstra
2022-08-29 13:10 ` Florian Weimer
2022-08-29 15:27 ` Wilco Dijkstra
2022-08-29 15:27 ` Wilco Dijkstra
2022-08-29 19:43 ` H.J. Lu
2022-08-29 19:57 ` Fangrui Song [this message]
2022-09-05 8:58 ` Wilco Dijkstra
2022-09-15 21:45 ` Fangrui Song
2022-09-20 13:59 ` Wilco Dijkstra
2022-09-20 14:12 ` Florian Weimer
2022-09-20 16:00 ` Wilco Dijkstra
2022-09-20 22:02 ` Fangrui Song
-- strict thread matches above, loose matches on Subject: below --
2022-08-25 21:01 Richard Henderson
2022-08-26 12:32 ` Adhemerval Zanella Netto
2022-08-26 17:29 ` Richard Henderson
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