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Date: Mon, 28 Sep 2020 15:48:54 -0700 From: Nathan Chancellor <natechancellor@...il.com> To: Kees Cook <keescook@...omium.org>, Ingo Molnar <mingo@...nel.org> Cc: Russell King <linux@...linux.org.uk>, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com, Nathan Chancellor <natechancellor@...il.com>, kernel test robot <lkp@...el.com> Subject: [PATCH] arm/build: Always handle .ARM.exidx and .ARM.extab sections After turning on warnings for orphan section placement, enabling CONFIG_UNWINDER_FRAME_POINTER instead of CONFIG_UNWINDER_ARM causes thousands of warnings when clang + ld.lld are used: $ scripts/config --file arch/arm/configs/multi_v7_defconfig \ -d CONFIG_UNWINDER_ARM \ -e CONFIG_UNWINDER_FRAME_POINTER $ make -skj"$(nproc)" ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- LLVM=1 defconfig zImage ld.lld: warning: init/built-in.a(main.o):(.ARM.extab) is being placed in '.ARM.extab' ld.lld: warning: init/built-in.a(main.o):(.ARM.extab.init.text) is being placed in '.ARM.extab.init.text' ld.lld: warning: init/built-in.a(main.o):(.ARM.extab.ref.text) is being placed in '.ARM.extab.ref.text' ld.lld: warning: init/built-in.a(do_mounts.o):(.ARM.extab.init.text) is being placed in '.ARM.extab.init.text' ld.lld: warning: init/built-in.a(do_mounts.o):(.ARM.extab) is being placed in '.ARM.extab' ld.lld: warning: init/built-in.a(do_mounts_rd.o):(.ARM.extab.init.text) is being placed in '.ARM.extab.init.text' ld.lld: warning: init/built-in.a(do_mounts_rd.o):(.ARM.extab) is being placed in '.ARM.extab' ld.lld: warning: init/built-in.a(do_mounts_initrd.o):(.ARM.extab.init.text) is being placed in '.ARM.extab.init.text' ld.lld: warning: init/built-in.a(initramfs.o):(.ARM.extab.init.text) is being placed in '.ARM.extab.init.text' ld.lld: warning: init/built-in.a(initramfs.o):(.ARM.extab) is being placed in '.ARM.extab' ld.lld: warning: init/built-in.a(calibrate.o):(.ARM.extab.init.text) is being placed in '.ARM.extab.init.text' ld.lld: warning: init/built-in.a(calibrate.o):(.ARM.extab) is being placed in '.ARM.extab' These sections are handled by the ARM_UNWIND_SECTIONS define, which is only added to the list of sections when CONFIG_ARM_UNWIND is set. CONFIG_ARM_UNWIND is a hidden symbol that is only selected when CONFIG_UNWINDER_ARM is set so CONFIG_UNWINDER_FRAME_POINTER never handles these sections. According to the help text of CONFIG_UNWINDER_ARM, these sections should be discarded so that the kernel image size is not affected. Fixes: 5a17850e251a ("arm/build: Warn on orphan section placement") Link: https://github.com/ClangBuiltLinux/linux/issues/1152 Reported-by: kernel test robot <lkp@...el.com> Signed-off-by: Nathan Chancellor <natechancellor@...il.com> --- arch/arm/kernel/vmlinux.lds.S | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S index 5f4922e858d0..a2c0d96b0580 100644 --- a/arch/arm/kernel/vmlinux.lds.S +++ b/arch/arm/kernel/vmlinux.lds.S @@ -40,6 +40,10 @@ SECTIONS ARM_DISCARD #ifndef CONFIG_SMP_ON_UP *(.alt.smp.init) +#endif +#ifndef CONFIG_ARM_UNWIND + *(.ARM.exidx*) + *(.ARM.extab*) #endif } base-commit: 6e0bf0e0e55000742a53c5f3b58f8669e0091a11 -- 2.28.0
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