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287d163322
While the GCC and Clang compilers already define __ASSEMBLER__ automatically when compiling assembly code, __ASSEMBLY__ is a macro that only gets defined by the Makefiles in the kernel. This can be very confusing when switching between userspace and kernelspace coding, or when dealing with uapi headers that rather should use __ASSEMBLER__ instead. So let's standardize now on the __ASSEMBLER__ macro that is provided by the compilers. This is a mostly mechanical patch (done with a simple "sed -i" statement), except for the following files where comments with mis-spelled macros were tweaked manually: arch/arm64/include/asm/stacktrace/frame.h arch/arm64/include/asm/kvm_ptrauth.h arch/arm64/include/asm/debug-monitors.h arch/arm64/include/asm/esr.h arch/arm64/include/asm/scs.h arch/arm64/include/asm/memory.h Signed-off-by: Thomas Huth <thuth@redhat.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
70 lines
1.8 KiB
C
70 lines
1.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Copyright (C) 2020 Google LLC.
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*/
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#ifndef __ASM_RWONCE_H
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#define __ASM_RWONCE_H
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#if defined(CONFIG_LTO) && !defined(__ASSEMBLER__)
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#include <linux/compiler_types.h>
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#include <asm/alternative-macros.h>
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#ifndef BUILD_VDSO
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#define __LOAD_RCPC(sfx, regs...) \
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ALTERNATIVE( \
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"ldar" #sfx "\t" #regs, \
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".arch_extension rcpc\n" \
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"ldapr" #sfx "\t" #regs, \
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ARM64_HAS_LDAPR)
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/*
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* When building with LTO, there is an increased risk of the compiler
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* converting an address dependency headed by a READ_ONCE() invocation
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* into a control dependency and consequently allowing for harmful
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* reordering by the CPU.
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*
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* Ensure that such transformations are harmless by overriding the generic
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* READ_ONCE() definition with one that provides RCpc acquire semantics
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* when building with LTO.
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*/
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#define __READ_ONCE(x) \
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({ \
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typeof(&(x)) __x = &(x); \
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int atomic = 1; \
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union { __unqual_scalar_typeof(*__x) __val; char __c[1]; } __u; \
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switch (sizeof(x)) { \
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case 1: \
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asm volatile(__LOAD_RCPC(b, %w0, %1) \
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: "=r" (*(__u8 *)__u.__c) \
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: "Q" (*__x) : "memory"); \
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break; \
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case 2: \
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asm volatile(__LOAD_RCPC(h, %w0, %1) \
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: "=r" (*(__u16 *)__u.__c) \
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: "Q" (*__x) : "memory"); \
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break; \
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case 4: \
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asm volatile(__LOAD_RCPC(, %w0, %1) \
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: "=r" (*(__u32 *)__u.__c) \
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: "Q" (*__x) : "memory"); \
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break; \
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case 8: \
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asm volatile(__LOAD_RCPC(, %0, %1) \
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: "=r" (*(__u64 *)__u.__c) \
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: "Q" (*__x) : "memory"); \
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break; \
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default: \
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atomic = 0; \
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} \
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atomic ? (typeof(*__x))__u.__val : (*(volatile typeof(__x))__x);\
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})
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#endif /* !BUILD_VDSO */
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#endif /* CONFIG_LTO && !__ASSEMBLER__ */
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#include <asm-generic/rwonce.h>
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#endif /* __ASM_RWONCE_H */
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