From: Alan Modra <amodra@gmail.com>
To: Fangrui Song <i@maskray.me>
Cc: Fangrui Song <maskray@google.com>, binutils@sourceware.org
Subject: Re: [PATCH] ld: Add -z start-stop-gc to let __start_/__stop_ not retain C identifier name sections
Date: Mon, 1 Mar 2021 17:58:29 +1030 [thread overview]
Message-ID: <20210301072829.GD6042@bubble.grove.modra.org> (raw)
In-Reply-To: <20210301070319.5pi24f4i7yrt5fmy@gmail.com>
On Sun, Feb 28, 2021 at 11:03:19PM -0800, Fangrui Song wrote:
> Here is another interesting test.
>
> .weak __start_xx
> .weak __stop_xx
>
> .global _start
> _start:
> movq __start_xx@gotpcrel(%rip), %rdi
> movq __stop_xx@gotpcrel(%rip), %rsi
>
> .section xx,"a",unique,0
> .byte 0
>
> .section xx,"a",unique,1
> .byte 1
>
> .section xx,"a",unique,2
> .byte 2
>
>
> ld-new a.o --gc-sections --print-gc-sections -pie -z start-stop-gc can discard 3 sections.
> ld-new a.o --gc-sections --print-gc-sections -shared -z start-stop-gc can only discard 2 - there may be a lurking bug somewhere.
I see
./ld-new: removing unused section 'xx' in file 'a.o'
./ld-new: removing unused section 'xx' in file 'a.o'
./ld-new: removing unused section 'xx' in file 'a.o'
./ld-new: a.o: relocation R_X86_64_PC32 against undefined protected symbol `__start_xx' can not be used when making a shared object
./ld-new: final link failed: bad value
I'm guessing that an x86 optimisation is being confused.
--
Alan Modra
Australia Development Lab, IBM
next prev parent reply other threads:[~2021-03-01 7:28 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-27 20:26 Fangrui Song
2021-02-27 23:47 ` H.J. Lu
2021-02-28 1:50 ` Fangrui Song
2021-02-28 2:49 ` H.J. Lu
2021-02-28 4:20 ` Alan Modra
2021-02-28 5:03 ` Fangrui Song
2021-03-01 3:59 ` Alan Modra
2021-03-01 7:03 ` Fangrui Song
2021-03-01 7:28 ` Alan Modra [this message]
2021-03-01 8:08 ` Fangrui Song
2021-03-01 4:04 ` Alan Modra
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