From: Will Deacon will@kernel.org
mainline inclusion from mainline-v5.11-rc1 commit e35123d83ee35c31f64ecfbdfabbe5142d3025b8 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I7LP2Z
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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When building with LTO, there is an increased risk of the compiler converting an address dependency headed by a READ_ONCE() invocation into a control dependency and consequently allowing for harmful reordering by the CPU.
Ensure that such transformations are harmless by overriding the generic READ_ONCE() definition with one that provides acquire semantics when building with LTO.
Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: Mark Rutland mark.rutland@arm.com Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Zeng Heng zengheng4@huawei.com --- arch/arm64/include/asm/rwonce.h | 73 +++++++++++++++++++++++++++++++ arch/arm64/kernel/vdso/Makefile | 2 +- arch/arm64/kernel/vdso32/Makefile | 2 +- arch/arm64/kernel/vmlinux.lds.S | 2 +- 4 files changed, 76 insertions(+), 3 deletions(-) create mode 100644 arch/arm64/include/asm/rwonce.h
diff --git a/arch/arm64/include/asm/rwonce.h b/arch/arm64/include/asm/rwonce.h new file mode 100644 index 000000000000..1bce62fa908a --- /dev/null +++ b/arch/arm64/include/asm/rwonce.h @@ -0,0 +1,73 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) 2020 Google LLC. + */ +#ifndef __ASM_RWONCE_H +#define __ASM_RWONCE_H + +#ifdef CONFIG_LTO + +#include <linux/compiler_types.h> +#include <asm/alternative-macros.h> + +#ifndef BUILD_VDSO + +#ifdef CONFIG_AS_HAS_LDAPR +#define __LOAD_RCPC(sfx, regs...) \ + ALTERNATIVE( \ + "ldar" #sfx "\t" #regs, \ + ".arch_extension rcpc\n" \ + "ldapr" #sfx "\t" #regs, \ + ARM64_HAS_LDAPR) +#else +#define __LOAD_RCPC(sfx, regs...) "ldar" #sfx "\t" #regs +#endif /* CONFIG_AS_HAS_LDAPR */ + +/* + * When building with LTO, there is an increased risk of the compiler + * converting an address dependency headed by a READ_ONCE() invocation + * into a control dependency and consequently allowing for harmful + * reordering by the CPU. + * + * Ensure that such transformations are harmless by overriding the generic + * READ_ONCE() definition with one that provides RCpc acquire semantics + * when building with LTO. + */ +#define __READ_ONCE(x) \ +({ \ + typeof(&(x)) __x = &(x); \ + int atomic = 1; \ + union { __unqual_scalar_typeof(*__x) __val; char __c[1]; } __u; \ + switch (sizeof(x)) { \ + case 1: \ + asm volatile(__LOAD_RCPC(b, %w0, %1) \ + : "=r" (*(__u8 *)__u.__c) \ + : "Q" (*__x) : "memory"); \ + break; \ + case 2: \ + asm volatile(__LOAD_RCPC(h, %w0, %1) \ + : "=r" (*(__u16 *)__u.__c) \ + : "Q" (*__x) : "memory"); \ + break; \ + case 4: \ + asm volatile(__LOAD_RCPC(, %w0, %1) \ + : "=r" (*(__u32 *)__u.__c) \ + : "Q" (*__x) : "memory"); \ + break; \ + case 8: \ + asm volatile(__LOAD_RCPC(, %0, %1) \ + : "=r" (*(__u64 *)__u.__c) \ + : "Q" (*__x) : "memory"); \ + break; \ + default: \ + atomic = 0; \ + } \ + atomic ? (typeof(*__x))__u.__val : (*(volatile typeof(__x))__x);\ +}) + +#endif /* !BUILD_VDSO */ +#endif /* CONFIG_LTO */ + +#include <asm-generic/rwonce.h> + +#endif /* __ASM_RWONCE_H */ diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile index d65f52264aba..a8f8e409e2bf 100644 --- a/arch/arm64/kernel/vdso/Makefile +++ b/arch/arm64/kernel/vdso/Makefile @@ -28,7 +28,7 @@ ldflags-y := -shared -nostdlib -soname=linux-vdso.so.1 --hash-style=sysv \ $(btildflags-y) -T
ccflags-y := -fno-common -fno-builtin -fno-stack-protector -ffixed-x18 -ccflags-y += -DDISABLE_BRANCH_PROFILING +ccflags-y += -DDISABLE_BRANCH_PROFILING -DBUILD_VDSO
CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS) $(GCC_PLUGINS_CFLAGS) KASAN_SANITIZE := n diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile index abad38c576e1..57b28f1e5d97 100644 --- a/arch/arm64/kernel/vdso32/Makefile +++ b/arch/arm64/kernel/vdso32/Makefile @@ -37,7 +37,7 @@ cc32-as-instr = $(call try-run,\ # As a result we set our own flags here.
# KBUILD_CPPFLAGS and NOSTDINC_FLAGS from top-level Makefile -VDSO_CPPFLAGS := -D__KERNEL__ -nostdinc +VDSO_CPPFLAGS := -DBUILD_VDSO -D__KERNEL__ -nostdinc VDSO_CPPFLAGS += -isystem $(shell $(CC_COMPAT) -print-file-name=include 2>/dev/null) VDSO_CPPFLAGS += $(LINUXINCLUDE)
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 71f4b5f24d15..31fdb55cd4e2 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -199,7 +199,7 @@ SECTIONS INIT_CALLS CON_INITCALL INIT_RAM_FS - *(.init.rodata.* .init.bss) /* from the EFI stub */ + *(.init.altinstructions .init.rodata.* .init.bss) /* from the EFI stub */ } .exit.data : { EXIT_DATA