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From: Nathan Chancellor <natechancellor@gmail.com>
To: "Maciej W. Rozycki" <macro@linux-mips.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Masahiro Yamada <masahiroy@kernel.org>,
	linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org,
	clang-built-linux@googlegroups.com, linux-kbuild@vger.kernel.org,
	Nick Desaulniers <ndesaulniers@google.com>,
	Fangrui Song <maskray@google.com>,
	Sami Tolvanen <samitolvanen@google.com>,
	Dmitry Golovin <dima@golovin.in>,
	Sedat Dilek <sedat.dilek@gmail.com>
Subject: Re: [PATCH v4 4/5] MIPS: VDSO: Use $(LD) instead of $(CC) to link VDSO
Date: Sat, 2 May 2020 08:49:45 -0700	[thread overview]
Message-ID: <20200502154945.GA3361319@ubuntu-s3-xlarge-x86> (raw)
In-Reply-To: <alpine.LFD.2.21.2005021435100.3602499@eddie.linux-mips.org>

On Sat, May 02, 2020 at 02:50:34PM +0100, Maciej W. Rozycki wrote:
> On Tue, 28 Apr 2020, Nathan Chancellor wrote:
> 
> > Before this patch, LD=ld.lld did nothing:
> > 
> > $ llvm-readelf -p.comment arch/mips/vdso/vdso.so.dbg | sed 's/(.*//'
> > String dump of section '.comment':
> > [     0] ClangBuiltLinux clang version 11.0.0
> 
>  What does it mean "did nothing", is `arch/mips/vdso/vdso.so.dbg.raw' not 
> produced?  Where does `arch/mips/vdso/vdso.so.dbg' come from then?
> 
>   Maciej

A better wording might be "Before this patch, specifying a linker like
ld.lld via the LD variable was not respected by the MIPS VDSO". I should
also probably expand on the second paragraph, maybe something like:

When clang is built in a default configuration, it first attempts to use
the target triple's default linker then the system's default linker,
which is almost always ld.bfd. To use ld.lld, '-fuse-ld=lld' must be
passed to clang. However, we do not use -fuse-ld=lld because it can be
brittle and we have support for invoking $(LD) directly because we have
separate compilation and link steps. See commit fe00e50b2db8c ("ARM:
8858/1: vdso: use $(LD) instead of $(CC) to link VDSO") and
commit 691efbedc60d2 ("arm64: vdso: use $(LD) instead of $(CC) to link
VDSO") for examples of doing this in the VDSO.

  reply	other threads:[~2020-05-02 15:49 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-19 18:04 [PATCH 1/2] kbuild: add CONFIG_LD_IS_LLD Nathan Chancellor
2020-04-19 18:04 ` [PATCH 2/2] MIPS: VDSO: Do not disable VDSO when linking with ld.lld Nathan Chancellor
2020-04-19 18:17   ` Nathan Chancellor
2020-04-19 19:32     ` Masahiro Yamada
2020-04-19 20:05       ` Nathan Chancellor
2020-04-19 20:21 ` [PATCH v2 1/3] kbuild: add CONFIG_LD_IS_LLD Nathan Chancellor
2020-04-19 20:21   ` [PATCH v2 2/3] MIPS: VDSO: Move disabling the VDSO logic to Kconfig Nathan Chancellor
2020-04-20  9:53     ` Sedat Dilek
2020-04-21  2:42       ` Nathan Chancellor
2020-04-23 14:41         ` Masahiro Yamada
2020-04-19 20:21   ` [PATCH v2 3/3] MIPS: VDSO: Allow ld.lld to link the VDSO Nathan Chancellor
2020-04-23 14:38   ` [PATCH v2 1/3] kbuild: add CONFIG_LD_IS_LLD Masahiro Yamada
2020-04-23 17:18   ` [PATCH v3 1/4] " Nathan Chancellor
2020-04-23 17:18     ` [PATCH v3 2/4] MIPS: VDSO: Move disabling the VDSO logic to Kconfig Nathan Chancellor
2020-04-23 17:18     ` [PATCH v3 3/4] MIPS: VDSO: Use $(LD) instead of $(CC) to link VDSO Nathan Chancellor
2020-04-26 16:27       ` Thomas Bogendoerfer
2020-04-27  2:08         ` Nathan Chancellor
2020-04-27 16:22           ` Maciej W. Rozycki
2020-04-27 23:24             ` Nathan Chancellor
2020-04-29 17:46               ` Maciej W. Rozycki
2020-04-30  3:14                 ` Nathan Chancellor
2020-04-28  2:17         ` Nathan Chancellor
2020-04-23 17:18     ` [PATCH v3 4/4] MIPS: VDSO: Allow ld.lld to link the VDSO Nathan Chancellor
2020-04-28 22:14     ` [PATCH v5 0/5] Allow ld.lld to link the MIPS VDSO Nathan Chancellor
2020-04-28 22:14       ` [PATCH v4 1/5] kbuild: add CONFIG_LD_IS_LLD Nathan Chancellor
2020-04-29  7:13         ` Sedat Dilek
2020-04-30  3:05           ` Nathan Chancellor
2020-04-28 22:14       ` [PATCH v4 2/5] MIPS: VDSO: Move disabling the VDSO logic to Kconfig Nathan Chancellor
2020-04-28 22:14       ` [PATCH v4 3/5] MIPS: Unconditionally specify '-EB' or '-EL' Nathan Chancellor
2020-04-28 22:14       ` [PATCH v4 4/5] MIPS: VDSO: Use $(LD) instead of $(CC) to link VDSO Nathan Chancellor
2020-04-28 22:54         ` Fangrui Song
2020-04-29  0:44           ` Nathan Chancellor
2020-05-02 13:34           ` Maciej W. Rozycki
2020-05-02 13:50         ` Maciej W. Rozycki
2020-05-02 15:49           ` Nathan Chancellor [this message]
2020-04-28 22:14       ` [PATCH v4 5/5] MIPS: VDSO: Allow ld.lld to link the VDSO Nathan Chancellor
2020-04-29  7:04       ` [PATCH v5 0/5] Allow ld.lld to link the MIPS VDSO Sedat Dilek
2020-04-30  3:06         ` Nathan Chancellor
2020-05-12  8:05       ` Thomas Bogendoerfer
2020-05-12  8:28         ` Nathan Chancellor
2020-05-13 11:18           ` Thomas Bogendoerfer

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