| 186,6 → 186,80 |
|---|
| # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__) |
| #endif |
| |
| #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) |
| { |
| 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(); |
| } |
| } |
| |
| static __always_inline void __assign_once_size(volatile void *p, void *res, int size) |
| { |
| switch (size) { |
| 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(); |
| } |
| } |
| |
| /* |
| * Prevent the compiler from merging or refetching reads or writes. The |
| * compiler is also forbidden from reordering successive instances of |
| * READ_ONCE, ASSIGN_ONCE and ACCESS_ONCE (see below), 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, |
| * ASSIGN_ONCE or ACCESS_ONCE() in different C statements. |
| * |
| * In contrast to ACCESS_ONCE these two macros will also work on aggregate |
| * data types like structs or unions. If the size of the accessed data |
| * type exceeds the word size of the machine (e.g., 32 bits or 64 bits) |
| * READ_ONCE() and ASSIGN_ONCE() will fall back to memcpy and print a |
| * compile-time warning. |
| * |
| * 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. |
| */ |
| |
| #define READ_ONCE(x) \ |
| ({ typeof(x) __val; __read_once_size(&x, &__val, sizeof(__val)); __val; }) |
| |
| #define ASSIGN_ONCE(val, x) \ |
| ({ typeof(x) __val; __val = val; __assign_once_size(&x, &__val, sizeof(__val)); __val; }) |
| |
| #endif /* __KERNEL__ */ |
| |
| #endif /* __ASSEMBLY__ */ |