# define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
#endif
-#include <uapi/linux/types.h>
-
-#define __READ_ONCE_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; \
- case 8: *(__u64 *)res = *(volatile __u64 *)p; break; \
- default: \
- barrier(); \
- __builtin_memcpy((void *)res, (const void *)p, size); \
- barrier(); \
- } \
-})
-
-static __always_inline
-void __read_once_size(const volatile void *p, void *res, int size)
-{
- __READ_ONCE_SIZE;
-}
-
-#ifdef CONFIG_KASAN
-/*
- * We can't declare function 'inline' because __no_sanitize_address confilcts
- * with inlining. Attempt to inline it may cause a build failure.
- * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
- * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
- */
-# define __no_kasan_or_inline __no_sanitize_address notrace __maybe_unused
-#else
-# define __no_kasan_or_inline __always_inline
-#endif
-
-static __no_kasan_or_inline
-void __read_once_size_nocheck(const volatile void *p, void *res, int size)
-{
- __READ_ONCE_SIZE;
-}
-
-static __always_inline void __write_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;
- case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
- default:
- barrier();
- __builtin_memcpy((void *)p, (const void *)res, size);
- barrier();
- }
-}
-
/*
* Prevent the compiler from merging or refetching reads or writes. The
* compiler is also forbidden from reordering successive instances of
* statements.
*
* 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 WRITE_ONCE() will
- * fall back to memcpy(). There's at least two memcpy()s: one for the
- * __builtin_memcpy() and then one for the macro doing the copy of variable
- * - '__u' allocated on the stack.
+ * unions.
*
* Their two major use cases are: (1) Mediating communication between
* process-level code and irq/NMI handlers, all running on the same CPU,
#include <asm/barrier.h>
#include <linux/kasan-checks.h>
-#define __READ_ONCE(x, check) \
+/*
+ * Use __READ_ONCE() instead of READ_ONCE() if you do not require any
+ * atomicity or dependency ordering guarantees. Note that this may result
+ * in tears!
+ */
+#define __READ_ONCE(x) (*(const volatile __unqual_scalar_typeof(x) *)&(x))
+
+#define __READ_ONCE_SCALAR(x) \
({ \
- union { typeof(x) __val; char __c[1]; } __u; \
- if (check) \
- __read_once_size(&(x), __u.__c, sizeof(x)); \
- else \
- __read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \
- smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
- __u.__val; \
+ __unqual_scalar_typeof(x) __x = __READ_ONCE(x); \
+ smp_read_barrier_depends(); \
+ (typeof(x))__x; \
})
-#define READ_ONCE(x) __READ_ONCE(x, 1)
+#define READ_ONCE(x) \
+({ \
+ compiletime_assert_rwonce_type(x); \
+ __READ_ONCE_SCALAR(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)
+
+#ifdef CONFIG_KASAN
/*
- * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
- * to hide memory access from KASAN.
+ * We can't declare function 'inline' because __no_sanitize_address conflicts
+ * with inlining. Attempt to inline it may cause a build failure.
+ * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
+ * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
*/
-#define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
+# define __no_kasan_or_inline __no_sanitize_address notrace __maybe_unused
+#else
+# define __no_kasan_or_inline __always_inline
+#endif
+
+static __no_kasan_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. This is usually
+ * used by unwinding code when walking the stack of a running process.
+ */
+#define READ_ONCE_NOCHECK(x) \
+({ \
+ unsigned long __x; \
+ compiletime_assert(sizeof(x) == sizeof(__x), \
+ "Unsupported access size for READ_ONCE_NOCHECK()."); \
+ __x = __read_once_word_nocheck(&(x)); \
+ smp_read_barrier_depends(); \
+ (typeof(x))__x; \
+})
static __no_kasan_or_inline
unsigned long read_word_at_a_time(const void *addr)
return *(unsigned long *)addr;
}
-#define WRITE_ONCE(x, val) \
-({ \
- union { typeof(x) __val; char __c[1]; } __u = \
- { .__val = (__force typeof(x)) (val) }; \
- __write_once_size(&(x), __u.__c, sizeof(x)); \
- __u.__val; \
-})
-
#endif /* __KERNEL__ */
/*
compiletime_assert(__native_word(t), \
"Need native word sized stores/loads for atomicity.")
+/*
+ * 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().")
+
/* &a[0] degrades to a pointer: a different type from an array */
#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
projects / linux-2.6-microblaze.git / blobdiff