From: Mark Rutland <mark.rutland@arm.com>
To: linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
clang-built-linux@googlegroups.com
Cc: Nathan Chancellor <natechancellor@gmail.com>,
Nick Desaulniers <ndesaulniers@google.com>
Subject: Enabling UBSAN breaks KCOV in clang (8.0.*) on arm64
Date: Mon, 19 Aug 2019 17:59:48 +0100 [thread overview]
Message-ID: <20190819165947.GA30292@lakrids.cambridge.arm.com> (raw)
Hi,
I found that when I enable both KCOV and UBSAN on arm64, clang fails to
emit any __sanitizer_cov_trace_*() calls in the resulting binary,
rendering KCOV useless.
For example, when building v5.3-rc3's arch/arm64/kernel/setup.o:
* With defconfig + CONFIG KCOV:
clang -Wp,-MD,arch/arm64/kernel/.setup.o.d -nostdinc -isystem
/mnt/data/opt/toolchain/llvm/8.0.0/clang+llvm-8.0.0-x86_64-linux-sles11.3/lib/clang/8.0.0/include
-I./arch/arm64/include -I./arch/arm64/include/generated -I./include
-I./arch/arm64/include/uapi -I./arch/arm64/include/generated/uapi
-I./include/uapi -I./include/generated/uapi -include
./include/linux/kconfig.h -include ./include/linux/compiler_types.h
-D__KERNEL__ -mlittle-endian -DKASAN_SHADOW_SCALE_SHIFT=3
-Qunused-arguments -Wall -Wundef -Werror=strict-prototypes
-Wno-trigraphs -fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE
-Werror=implicit-function-declaration -Werror=implicit-int
-Wno-format-security -std=gnu89 --target=aarch64-linux
--prefix=/mnt/data/opt/toolchain/kernel-org-crosstool/gcc-8.1.0-nolibc/aarch64-linux/bin/
--gcc-toolchain=/mnt/data/opt/toolchain/kernel-org-crosstool/gcc-8.1.0-nolibc/aarch64-linux
-no-integrated-as -Werror=unknown-warning-option -mgeneral-regs-only
-DCONFIG_AS_LSE=1 -fno-asynchronous-unwind-tables
-DKASAN_SHADOW_SCALE_SHIFT=3 -fno-delete-null-pointer-checks
-Wno-address-of-packed-member -O2 -Wframe-larger-than=2048
-fstack-protector-strong -Wno-format-invalid-specifier -Wno-gnu
-Wno-tautological-compare -mno-global-merge -Wno-unused-const-variable
-fno-omit-frame-pointer -fno-optimize-sibling-calls -g
-Wdeclaration-after-statement -Wvla -Wno-pointer-sign
-fno-strict-overflow -fno-merge-all-constants -fno-stack-check
-Werror=date-time -Werror=incompatible-pointer-types
-Wno-initializer-overrides -Wno-format -Wno-sign-compare
-Wno-format-zero-length -fsanitize-coverage=trace-pc
-DKBUILD_BASENAME='"setup"' -DKBUILD_MODNAME='"setup"' -c -o
arch/arm64/kernel/setup.o arch/arm64/kernel/setup.c
... and there are 44 calls to __sanitizer_cov_trace_pc in the
resulting setup.o
* with defconfig + CONFIG_KCOV + CONFIG_UBSAN:
clang -Wp,-MD,arch/arm64/kernel/.setup.o.d -nostdinc -isystem
/mnt/data/opt/toolchain/llvm/8.0.0/clang+llvm-8.0.0-x86_64-linux-sles11.3/lib/clang/8.0.0/include
-I./arch/arm64/include -I./arch/arm64/include/generated -I./include
-I./arch/arm64/include/uapi -I./arch/arm64/include/generated/uapi
-I./include/uapi -I./include/generated/uapi -include
./include/linux/kconfig.h -include ./include/linux/compiler_types.h
-D__KERNEL__ -mlittle-endian -DKASAN_SHADOW_SCALE_SHIFT=3
-Qunused-arguments -Wall -Wundef -Werror=strict-prototypes
-Wno-trigraphs -fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE
-Werror=implicit-function-declaration -Werror=implicit-int
-Wno-format-security -std=gnu89 --target=aarch64-linux
--prefix=/mnt/data/opt/toolchain/kernel-org-crosstool/gcc-8.1.0-nolibc/aarch64-linux/bin/
--gcc-toolchain=/mnt/data/opt/toolchain/kernel-org-crosstool/gcc-8.1.0-nolibc/aarch64-linux
-no-integrated-as -Werror=unknown-warning-option -mgeneral-regs-only
-DCONFIG_AS_LSE=1 -fno-asynchronous-unwind-tables
-DKASAN_SHADOW_SCALE_SHIFT=3 -fno-delete-null-pointer-checks
-Wno-address-of-packed-member -O2 -Wframe-larger-than=2048
-fstack-protector-strong -Wno-format-invalid-specifier -Wno-gnu
-Wno-tautological-compare -mno-global-merge -Wno-unused-const-variable
-fno-omit-frame-pointer -fno-optimize-sibling-calls -g
-Wdeclaration-after-statement -Wvla -Wno-pointer-sign
-fno-strict-overflow -fno-merge-all-constants -fno-stack-check
-Werror=date-time -Werror=incompatible-pointer-types
-Wno-initializer-overrides -Wno-format -Wno-sign-compare
-Wno-format-zero-length -fsanitize=shift
-fsanitize=integer-divide-by-zero -fsanitize=unreachable
-fsanitize=signed-integer-overflow -fsanitize=bounds
-fsanitize=object-size -fsanitize=bool -fsanitize=enum
-fsanitize-coverage=trace-pc -DKBUILD_BASENAME='"setup"'
-DKBUILD_MODNAME='"setup"' -c -o arch/arm64/kernel/setup.o
arch/arm64/kernel/setup.c
... and there are 0 calls to __sanitizer_cov_trace_pc in the resulting
setup.o, even though -fsanitize-coverage=trace-pc was passed to clang.
If I remove -fsanitize=bounds, there are 121 calls to
__sanitizer_cov_trace_pc in setup.o. Removing the other options enabled
by UBSAN didn't have any effect on setup.o.
I'm using the llvm.org 8.0.{0,1} binaries [1,2], along with the
kernel.org crosstool 8.1.0 binaries [3].
Any ideas as to what's going on?
Thanks,
Mark.
[1] http://releases.llvm.org/download.html#8.0.0
[2] http://releases.llvm.org/download.html#8.0.1
[3] https://mirrors.edge.kernel.org/pub/tools/crosstool/
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next reply other threads:[~2019-08-19 17:00 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-19 16:59 Mark Rutland [this message]
2019-08-20 7:28 ` Enabling UBSAN breaks KCOV in clang (8.0.*) on arm64 Nathan Chancellor
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