Date:   Thu, 16 Mar 2023 09:05:23 -0700
From:   Nathan Chancellor <nathan@kernel.org>
To:     Marco Elver <elver@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>, kasan-dev@googlegroups.com,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] kfence, kcsan: avoid passing -g for tests
Message-ID: <20230316160523.GA90073@dev-arch.thelio-3990X>
References: <20230316155104.594662-1-elver@google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20230316155104.594662-1-elver@google.com>
Precedence: bulk

On Thu, Mar 16, 2023 at 04:51:04PM +0100, Marco Elver wrote:
> Nathan reported that when building with GNU as and a version of clang
> that defaults to DWARF5:
> 
>   $ make -skj"$(nproc)" ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- \
> 			LLVM=1 LLVM_IAS=0 O=build \
> 			mrproper allmodconfig mm/kfence/kfence_test.o
>   /tmp/kfence_test-08a0a0.s: Assembler messages:
>   /tmp/kfence_test-08a0a0.s:14627: Error: non-constant .uleb128 is not supported
>   /tmp/kfence_test-08a0a0.s:14628: Error: non-constant .uleb128 is not supported
>   /tmp/kfence_test-08a0a0.s:14632: Error: non-constant .uleb128 is not supported
>   /tmp/kfence_test-08a0a0.s:14633: Error: non-constant .uleb128 is not supported
>   /tmp/kfence_test-08a0a0.s:14639: Error: non-constant .uleb128 is not supported
>   ...
> 
> This is because `-g` defaults to the compiler debug info default. If the
> assembler does not support some of the directives used, the above errors
> occur. To fix, remove the explicit passing of `-g`.
> 
> All these tests want is that stack traces print valid function names,
> and debug info is not required for that. I currently cannot recall why I
> added the explicit `-g`.
> 
> Reported-by: Nathan Chancellor <nathan@kernel.org>
> Signed-off-by: Marco Elver <elver@google.com>

Thanks for the quick patch!

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

> ---
>  kernel/kcsan/Makefile | 2 +-
>  mm/kfence/Makefile    | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/kcsan/Makefile b/kernel/kcsan/Makefile
> index 8cf70f068d92..a45f3dfc8d14 100644
> --- a/kernel/kcsan/Makefile
> +++ b/kernel/kcsan/Makefile
> @@ -16,6 +16,6 @@ obj-y := core.o debugfs.o report.o
>  KCSAN_INSTRUMENT_BARRIERS_selftest.o := y
>  obj-$(CONFIG_KCSAN_SELFTEST) += selftest.o
>  
> -CFLAGS_kcsan_test.o := $(CFLAGS_KCSAN) -g -fno-omit-frame-pointer
> +CFLAGS_kcsan_test.o := $(CFLAGS_KCSAN) -fno-omit-frame-pointer
>  CFLAGS_kcsan_test.o += $(DISABLE_STRUCTLEAK_PLUGIN)
>  obj-$(CONFIG_KCSAN_KUNIT_TEST) += kcsan_test.o
> diff --git a/mm/kfence/Makefile b/mm/kfence/Makefile
> index 0bb95728a784..2de2a58d11a1 100644
> --- a/mm/kfence/Makefile
> +++ b/mm/kfence/Makefile
> @@ -2,5 +2,5 @@
>  
>  obj-y := core.o report.o
>  
> -CFLAGS_kfence_test.o := -g -fno-omit-frame-pointer -fno-optimize-sibling-calls
> +CFLAGS_kfence_test.o := -fno-omit-frame-pointer -fno-optimize-sibling-calls
>  obj-$(CONFIG_KFENCE_KUNIT_TEST) += kfence_test.o
> -- 
> 2.40.0.rc1.284.g88254d51c5-goog
>