diff options
Diffstat (limited to 'include/linux/compiler.h')
| -rw-r--r-- | include/linux/compiler.h | 49 |
1 files changed, 24 insertions, 25 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 33063f872ee3..0e41ca0e5927 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -54,7 +54,11 @@ extern void __chk_io_ptr(const volatile void __iomem *); #include <linux/compiler-gcc.h> #endif +#ifdef CC_USING_HOTPATCH +#define notrace __attribute__((hotpatch(0,0))) +#else #define notrace __attribute__((no_instrument_function)) +#endif /* Intel compiler defines __GNUC__. So we will overwrite implementations * coming from above header files here @@ -188,29 +192,16 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect); #include <uapi/linux/types.h> -static __always_inline void data_access_exceeds_word_size(void) -#ifdef __compiletime_warning -__compiletime_warning("data access exceeds word size and won't be atomic") -#endif -; - -static __always_inline void data_access_exceeds_word_size(void) -{ -} - -static __always_inline void __read_once_size(volatile void *p, void *res, int size) +static __always_inline void __read_once_size(const volatile void *p, void *res, int size) { switch (size) { case 1: *(__u8 *)res = *(volatile __u8 *)p; break; case 2: *(__u16 *)res = *(volatile __u16 *)p; break; case 4: *(__u32 *)res = *(volatile __u32 *)p; break; -#ifdef CONFIG_64BIT case 8: *(__u64 *)res = *(volatile __u64 *)p; break; -#endif default: barrier(); __builtin_memcpy((void *)res, (const void *)p, size); - data_access_exceeds_word_size(); barrier(); } } @@ -221,13 +212,10 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s case 1: *(volatile __u8 *)p = *(__u8 *)res; break; case 2: *(volatile __u16 *)p = *(__u16 *)res; break; case 4: *(volatile __u32 *)p = *(__u32 *)res; break; -#ifdef CONFIG_64BIT case 8: *(volatile __u64 *)p = *(__u64 *)res; break; -#endif default: barrier(); __builtin_memcpy((void *)p, (const void *)res, size); - data_access_exceeds_word_size(); barrier(); } } @@ -255,10 +243,10 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s */ #define READ_ONCE(x) \ - ({ typeof(x) __val; __read_once_size(&x, &__val, sizeof(__val)); __val; }) + ({ union { typeof(x) __val; char __c[1]; } __u; __read_once_size(&(x), __u.__c, sizeof(x)); __u.__val; }) #define WRITE_ONCE(x, val) \ - ({ typeof(x) __val; __val = val; __write_once_size(&x, &__val, sizeof(__val)); __val; }) + ({ typeof(x) __val = (val); __write_once_size(&(x), &__val, sizeof(__val)); __val; }) #endif /* __KERNEL__ */ @@ -385,7 +373,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s /* Is this type a native word size -- useful for atomic operations */ #ifndef __native_word -# define __native_word(t) (sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long)) +# define __native_word(t) (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long)) #endif /* Compile time object size, -1 for unknown */ @@ -447,12 +435,23 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s * to make the compiler aware of ordering is to put the two invocations of * ACCESS_ONCE() in different C statements. * - * This macro does absolutely -nothing- to prevent the CPU from reordering, - * merging, or refetching absolutely anything at any time. Its main intended - * use is to mediate communication between process-level code and irq/NMI - * handlers, all running on the same CPU. + * ACCESS_ONCE will only work on scalar types. For union types, ACCESS_ONCE + * on a union member will work as long as the size of the member matches the + * size of the union and the size is smaller than word size. + * + * The major use cases of ACCESS_ONCE used to be (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. + * + * If possible use READ_ONCE/ASSIGN_ONCE instead. */ -#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x)) +#define __ACCESS_ONCE(x) ({ \ + __maybe_unused typeof(x) __var = (__force typeof(x)) 0; \ + (volatile typeof(x) *)&(x); }) +#define ACCESS_ONCE(x) (*__ACCESS_ONCE(x)) /* Ignore/forbid kprobes attach on very low level functions marked by this attribute: */ #ifdef CONFIG_KPROBES |