From: "H.J. Lu" <hjl.tools@gmail.com>
To: Fangrui Song <i@maskray.me>
Cc: Binutils <binutils@sourceware.org>
Subject: Re: [PATCH] x86: Keep __patchable_function_entries sections with --gc-sections
Date: Sat, 01 Feb 2020 17:43:00 -0000 [thread overview]
Message-ID: <CAMe9rOp0cFJLxW1K=av9F1HmS0q-CmmdFcx9LwTQiOddf=417g@mail.gmail.com> (raw)
In-Reply-To: <20200201173429.ep5siwkbhz5osehk@google.com>
On Sat, Feb 1, 2020 at 9:34 AM Fangrui Song <i@maskray.me> wrote:
>
> On 2020-02-01, H.J. Lu wrote:
> >After all text sections have been garbage collected, if a
> >__patchable_function_entries section references a section which
> >wasn't marked, mark it with SEC_EXCLUDE and return NULL. Otherwise,
> >keep it.
> >
> >Should it be handled in _bfd_elf_gc_mark_extra_sections?
>
> Thanks for paying attention to these feature requests.
>
> I referenced GNU as and ld requests at
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93492#c2
> If we
>
> * implement SHF_LINK_ORDER
I am not sure if overloading (abusing?) SHF_LINK_ORDER is a good idea.
> * allow multiple sections with the same name ("unique")
This is orthogonal to this. I have a question on assembly syntax:
https://sourceware.org/bugzilla/show_bug.cgi?id=25380#c1
> * teach GCC to use SHF_LINK_ORDER and "unique" (see https://gcc.gnu.org/ml/gcc/2020-01/msg00067.html)
>
> An ad-hoc gc marking will be unnecessary.
We need to scan relocations in _patchable_function_entries section for
references to garbage collected sections. We can either check section
name or a SHF_XXX. But I don't know if SHF_LINK_ORDER is a good
approach.
> SHF_LINK_ORDER has been used in a few sanitizers. Now we know
> __patchable_function_entries can benefit from it. In the future, they
> may be instances. We really need a general solution.
--
H.J.
next prev parent reply other threads:[~2020-02-01 17:43 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-01 16:26 H.J. Lu
2020-02-01 17:19 ` H.J. Lu
2020-02-01 17:34 ` Fangrui Song
2020-02-01 17:43 ` H.J. Lu [this message]
2020-02-01 18:21 ` Fangrui Song
2020-02-02 23:44 ` [PATCH] Issue an error for GC on __patchable_function_entries section H.J. Lu
2020-02-03 0:57 ` Fangrui Song
2020-02-03 1:18 ` H.J. Lu
2020-02-07 2:23 ` [PATCH] ld: " H.J. Lu
2020-02-07 3:28 ` Alan Modra
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