linux-kernel - [PATCH] kfence, kcsan: avoid passing -g for tests

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Date:   Thu, 16 Mar 2023 16:51:04 +0100
From:   Marco Elver <elver@...gle.com>
To:     elver@...gle.com, Andrew Morton <akpm@...ux-foundation.org>
Cc:     Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH] kfence, kcsan: avoid passing -g for tests

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@...nel.org>
Signed-off-by: Marco Elver <elver@...gle.com>
---
 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