diff options
Diffstat (limited to 'include/asm-generic')
| -rw-r--r-- | include/asm-generic/Kbuild | 1 | ||||
| -rw-r--r-- | include/asm-generic/barrier.h | 19 | ||||
| -rw-r--r-- | include/asm-generic/rwonce.h | 90 |
3 files changed, 92 insertions, 18 deletions
diff --git a/include/asm-generic/Kbuild b/include/asm-generic/Kbuild index 44ec80e70518..74b0612601dd 100644 --- a/include/asm-generic/Kbuild +++ b/include/asm-generic/Kbuild @@ -45,6 +45,7 @@ mandatory-y += pci.h mandatory-y += percpu.h mandatory-y += pgalloc.h mandatory-y += preempt.h +mandatory-y += rwonce.h mandatory-y += sections.h mandatory-y += serial.h mandatory-y += shmparam.h diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h index 2eacaf7d62f6..fec97dc34de7 100644 --- a/include/asm-generic/barrier.h +++ b/include/asm-generic/barrier.h @@ -13,7 +13,7 @@ #ifndef __ASSEMBLY__ -#include <linux/compiler.h> +#include <asm/rwonce.h> #ifndef nop #define nop() asm volatile ("nop") @@ -46,10 +46,6 @@ #define dma_wmb() wmb() #endif -#ifndef read_barrier_depends -#define read_barrier_depends() do { } while (0) -#endif - #ifndef __smp_mb #define __smp_mb() mb() #endif @@ -62,10 +58,6 @@ #define __smp_wmb() wmb() #endif -#ifndef __smp_read_barrier_depends -#define __smp_read_barrier_depends() read_barrier_depends() -#endif - #ifdef CONFIG_SMP #ifndef smp_mb @@ -80,10 +72,6 @@ #define smp_wmb() __smp_wmb() #endif -#ifndef smp_read_barrier_depends -#define smp_read_barrier_depends() __smp_read_barrier_depends() -#endif - #else /* !CONFIG_SMP */ #ifndef smp_mb @@ -98,10 +86,6 @@ #define smp_wmb() barrier() #endif -#ifndef smp_read_barrier_depends -#define smp_read_barrier_depends() do { } while (0) -#endif - #endif /* CONFIG_SMP */ #ifndef __smp_store_mb @@ -196,7 +180,6 @@ do { \ #define virt_mb() __smp_mb() #define virt_rmb() __smp_rmb() #define virt_wmb() __smp_wmb() -#define virt_read_barrier_depends() __smp_read_barrier_depends() #define virt_store_mb(var, value) __smp_store_mb(var, value) #define virt_mb__before_atomic() __smp_mb__before_atomic() #define virt_mb__after_atomic() __smp_mb__after_atomic() diff --git a/include/asm-generic/rwonce.h b/include/asm-generic/rwonce.h new file mode 100644 index 000000000000..8d0a6280e982 --- /dev/null +++ b/include/asm-generic/rwonce.h @@ -0,0 +1,90 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Prevent the compiler from merging or refetching reads or writes. The + * compiler is also forbidden from reordering successive instances of + * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some + * particular ordering. One way to make the compiler aware of ordering is to + * put the two invocations of READ_ONCE or WRITE_ONCE in different C + * statements. + * + * These two macros will also work on aggregate data types like structs or + * unions. + * + * Their two major use cases are: (1) Mediating communication between + * process-level code and irq/NMI handlers, all running on the same CPU, + * and (2) Ensuring that the compiler does not fold, spindle, or otherwise + * mutilate accesses that either do not require ordering or that interact + * with an explicit memory barrier or atomic instruction that provides the + * required ordering. + */ +#ifndef __ASM_GENERIC_RWONCE_H +#define __ASM_GENERIC_RWONCE_H + +#ifndef __ASSEMBLY__ + +#include <linux/compiler_types.h> +#include <linux/kasan-checks.h> +#include <linux/kcsan-checks.h> + +/* + * Yes, this permits 64-bit accesses on 32-bit architectures. These will + * actually be atomic in some cases (namely Armv7 + LPAE), but for others we + * rely on the access being split into 2x32-bit accesses for a 32-bit quantity + * (e.g. a virtual address) and a strong prevailing wind. + */ +#define compiletime_assert_rwonce_type(t) \ + compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \ + "Unsupported access size for {READ,WRITE}_ONCE().") + +/* + * Use __READ_ONCE() instead of READ_ONCE() if you do not require any + * atomicity. Note that this may result in tears! + */ +#ifndef __READ_ONCE +#define __READ_ONCE(x) (*(const volatile __unqual_scalar_typeof(x) *)&(x)) +#endif + +#define READ_ONCE(x) \ +({ \ + compiletime_assert_rwonce_type(x); \ + __READ_ONCE(x); \ +}) + +#define __WRITE_ONCE(x, val) \ +do { \ + *(volatile typeof(x) *)&(x) = (val); \ +} while (0) + +#define WRITE_ONCE(x, val) \ +do { \ + compiletime_assert_rwonce_type(x); \ + __WRITE_ONCE(x, val); \ +} while (0) + +static __no_sanitize_or_inline +unsigned long __read_once_word_nocheck(const void *addr) +{ + return __READ_ONCE(*(unsigned long *)addr); +} + +/* + * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need to load a + * word from memory atomically but without telling KASAN/KCSAN. This is + * usually used by unwinding code when walking the stack of a running process. + */ +#define READ_ONCE_NOCHECK(x) \ +({ \ + compiletime_assert(sizeof(x) == sizeof(unsigned long), \ + "Unsupported access size for READ_ONCE_NOCHECK()."); \ + (typeof(x))__read_once_word_nocheck(&(x)); \ +}) + +static __no_kasan_or_inline +unsigned long read_word_at_a_time(const void *addr) +{ + kasan_check_read(addr, 1); + return *(unsigned long *)addr; +} + +#endif /* __ASSEMBLY__ */ +#endif /* __ASM_GENERIC_RWONCE_H */ |