arm64: Do not include __READ_ONCE() block in assembly files
When building arm64 defconfig + CONFIG_LTO_CLANG_{FULL,THIN}=y after commit 558c303c ("arm64: Mitigate spectre style branch history side channels"), the following error occurs: <instantiation>:4:2: error: invalid fixup for movz/movk instruction mov w0, #ARM_SMCCC_ARCH_WORKAROUND_3 ^ Marc figured out that moving "#include <linux/init.h>" in include/linux/arm-smccc.h into a !__ASSEMBLY__ block resolves it. The full include chain with CONFIG_LTO=y from include/linux/arm-smccc.h: include/linux/init.h include/linux/compiler.h arch/arm64/include/asm/rwonce.h arch/arm64/include/asm/alternative-macros.h arch/arm64/include/asm/assembler.h The asm/alternative-macros.h include in asm/rwonce.h only happens when CONFIG_LTO is set, which ultimately casues asm/assembler.h to be included before the definition of ARM_SMCCC_ARCH_WORKAROUND_3. As a result, the preprocessor does not expand ARM_SMCCC_ARCH_WORKAROUND_3 in __mitigate_spectre_bhb_fw, which results in the error above. Avoid this problem by just avoiding the CONFIG_LTO=y __READ_ONCE() block in asm/rwonce.h with assembly files, as nothing in that block is useful to assembly files, which allows ARM_SMCCC_ARCH_WORKAROUND_3 to be properly expanded with CONFIG_LTO=y builds. Fixes: e35123d8 ("arm64: lto: Strengthen READ_ONCE() to acquire when CONFIG_LTO=y") Cc: <stable@vger.kernel.org> # 5.11.x Link: https://lore.kernel.org/r/20220309155716.3988480-1-maz@kernel.org/Reported-by: Marc Zyngier <maz@kernel.org> Acked-by: James Morse <james.morse@arm.com> Signed-off-by: Nathan Chancellor <nathan@kernel.org> Link: https://lore.kernel.org/r/20220309191633.2307110-1-nathan@kernel.orgSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>
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