From: Matthias Kaehlcke <mka@chromium.org>
To: Nathan Chancellor <natechancellor@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
Nick Desaulniers <ndesaulniers@google.com>,
Russell King <linux@armlinux.org.uk>,
Stefan Agner <stefan@agner.ch>,
linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] ARM: Emit __gnu_mcount_nc when using Clang 10.0.0 or newer
Date: Thu, 29 Aug 2019 09:20:38 -0700 [thread overview]
Message-ID: <20190829162038.GC70797@google.com> (raw)
In-Reply-To: <20190829062635.45609-1-natechancellor@gmail.com>
On Wed, Aug 28, 2019 at 11:26:35PM -0700, Nathan Chancellor wrote:
> Currently, multi_v7_defconfig + CONFIG_FUNCTION_TRACER fails to build
> with clang:
>
> arm-linux-gnueabi-ld: kernel/softirq.o: in function `_local_bh_enable':
> softirq.c:(.text+0x504): undefined reference to `mcount'
> arm-linux-gnueabi-ld: kernel/softirq.o: in function `__local_bh_enable_ip':
> softirq.c:(.text+0x58c): undefined reference to `mcount'
> arm-linux-gnueabi-ld: kernel/softirq.o: in function `do_softirq':
> softirq.c:(.text+0x6c8): undefined reference to `mcount'
> arm-linux-gnueabi-ld: kernel/softirq.o: in function `irq_enter':
> softirq.c:(.text+0x75c): undefined reference to `mcount'
> arm-linux-gnueabi-ld: kernel/softirq.o: in function `irq_exit':
> softirq.c:(.text+0x840): undefined reference to `mcount'
> arm-linux-gnueabi-ld: kernel/softirq.o:softirq.c:(.text+0xa50): more undefined references to `mcount' follow
>
> clang can emit a working mcount symbol, __gnu_mcount_nc, when
> '-meabi gnu' is passed to it. Until r369147 in LLVM, this was
> broken and caused the kernel not to boot because the calling
> convention was not correct. Now that it is fixed, add this to
> the command line when clang is 10.0.0 or newer so everything
> works properly.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/35
> Link: https://bugs.llvm.org/show_bug.cgi?id=33845
> Link: https://github.com/llvm/llvm-project/commit/16fa8b09702378bacfa3d07081afe6b353b99e60
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
> arch/arm/Makefile | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/arch/arm/Makefile b/arch/arm/Makefile
> index c3624ca6c0bc..7b5a26a866fc 100644
> --- a/arch/arm/Makefile
> +++ b/arch/arm/Makefile
> @@ -112,6 +112,12 @@ ifeq ($(CONFIG_ARM_UNWIND),y)
> CFLAGS_ABI +=-funwind-tables
> endif
>
> +ifeq ($(CONFIG_CC_IS_CLANG),y)
> +ifeq ($(shell test $(CONFIG_CLANG_VERSION) -ge 100000; echo $$?),0)
> +CFLAGS_ABI +=-meabi gnu
> +endif
> +endif
Is this also correct/needed when CONFIG_AEABI is not set?
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next prev parent reply other threads:[~2019-08-29 16:20 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-29 6:26 [PATCH] ARM: Emit __gnu_mcount_nc when using Clang 10.0.0 or newer Nathan Chancellor
2019-08-29 7:57 ` Stefan Agner
2019-08-29 16:20 ` Matthias Kaehlcke [this message]
2019-08-29 17:55 ` Nick Desaulniers
2019-08-29 19:34 ` Nathan Chancellor
2019-08-29 20:21 ` Stefan Agner
2019-08-29 20:57 ` Nick Desaulniers
2019-08-30 17:28 ` Nathan Chancellor
2019-08-30 21:13 ` Nick Desaulniers
2019-08-30 21:15 ` Nick Desaulniers
2019-08-31 6:05 ` [PATCH v2] " Nathan Chancellor
2019-09-03 18:48 ` Matthias Kaehlcke
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