From: Alan Modra <amodra@gmail.com>
To: "Maciej W. Rozycki" <macro@orcam.me.uk>
Cc: YunQiang Su <wzssyqa@gmail.com>,
YunQiang Su <yunqiang.su@cipunited.com>,
binutils@sourceware.org, Nick Clifton <nickc@redhat.com>
Subject: Re: [PATCH v2] MIPS: Don't move __gnu_lto_slim to .scommon
Date: Thu, 20 Jul 2023 20:53:59 +0930 [thread overview]
Message-ID: <ZLkZT4fA7WTAOJEA@squeak.grove.modra.org> (raw)
In-Reply-To: <alpine.DEB.2.21.2307201019570.14315@angie.orcam.me.uk>
On Thu, Jul 20, 2023 at 10:34:43AM +0100, Maciej W. Rozycki wrote:
> On Thu, 20 Jul 2023, Alan Modra wrote:
>
> > I think the patch is OK, but the same should be applied to another
> > place to stop objcopy modifying __gnu_lto_slim.
> >
> > mips-linux-gnu testcase after running make check:
> > binutils/objcopy ld/tmpdir/pr15323a-r.o ld/tmpdir/xxx
> > then inspect ld/tmpdir/xxx with readelf.
> >
> > I'm going to apply the following to mainline, and will also apply to
> > the 2.41 branch tomorrow if no one objects.
>
> You are the author of this code, so I guess you know what's going on
> here. I still don't understand the circumstances that cause linker.c to
> reject this symbol if it's in an SHN_MIPS_SCOMMON rather than SHN_COMMON
> section, and the relevant git change descriptions (going back to commit
> b794fc1d1c3a ("Warn for ar/nm/ranlib/ld on lto objects without plugin"))
> do not explain it, so I'd appreciate if you got me enlightened.
It isn't anything in linker.c, I believe the problem occurs in the lto
plugin which processes object files using libiberty/simple-object*.
Code in libiberty/simple-object-elf.c removes SHN_COMMON symbols,
which for most architectures removes __gnu_lto_slim, but not on mips
if the symbol is moved to SHN_MIPS_SCOMMON. Then the symbol appears
in lto output files, resulting in linker errors like:
/tmp/ccg5JkW9.debug.temp.o: plugin needed to handle lto object
I haven't actually looked at this under gdb to see exactly what is
going on for mips, I'm relying on memory from doing so for powerpc a
while ago.
--
Alan Modra
Australia Development Lab, IBM
next prev parent reply other threads:[~2023-07-20 11:24 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-03 10:36 [PATCH] MIPS: Don't " YunQiang Su
2023-07-03 10:50 ` [PATCH v2] MIPS: Don't move " YunQiang Su
2023-07-05 1:42 ` YunQiang Su
2023-07-13 5:39 ` YunQiang Su
2023-07-19 14:55 ` Maciej W. Rozycki
2023-07-19 17:26 ` YunQiang Su
2023-07-20 9:05 ` Alan Modra
2023-07-20 9:34 ` Maciej W. Rozycki
2023-07-20 11:23 ` Alan Modra [this message]
2023-07-20 14:32 ` Maciej W. Rozycki
2023-07-20 22:44 ` Alan Modra
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