# define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
#endif
-#include <uapi/linux/types.h>
+/*
+ * 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.
+ */
+#include <asm/barrier.h>
+#include <linux/kasan-checks.h>
+ #include <linux/kcsan-checks.h>
+
-#define __READ_ONCE_SIZE \
++/**
++ * data_race - mark an expression as containing intentional data races
++ *
++ * This data_race() macro is useful for situations in which data races
++ * should be forgiven. One example is diagnostic code that accesses
++ * shared variables but is not a part of the core synchronization design.
++ *
++ * This macro *does not* affect normal code generation, but is a hint
++ * to tooling that data races here are to be ignored.
++ */
++#define data_race(expr) \
+ ({ \
- 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(); \
- } \
++ __kcsan_disable_current(); \
++ ({ \
++ __unqual_scalar_typeof(({ expr; })) __v = ({ expr; }); \
++ __kcsan_enable_current(); \
++ __v; \
++ }); \
+ })
- __unqual_scalar_typeof(x) __x = __READ_ONCE(x); \
+/*
+ * 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) \
+({ \
- #define __WRITE_ONCE(x, val) \
- do { \
- *(volatile typeof(x) *)&(x) = (val); \
++ typeof(x) *__xp = &(x); \
++ __unqual_scalar_typeof(x) __x = data_race(__READ_ONCE(*__xp)); \
++ kcsan_check_atomic_read(__xp, sizeof(*__xp)); \
+ smp_read_barrier_depends(); \
+ (typeof(x))__x; \
+})
+
+#define READ_ONCE(x) \
+({ \
+ compiletime_assert_rwonce_type(x); \
+ __READ_ONCE_SCALAR(x); \
+})
+
- #define WRITE_ONCE(x, val) \
- do { \
- compiletime_assert_rwonce_type(x); \
- __WRITE_ONCE(x, val); \
++#define __WRITE_ONCE(x, val) \
++do { \
++ *(volatile typeof(x) *)&(x) = (val); \
++} while (0)
++
++#define __WRITE_ONCE_SCALAR(x, val) \
++do { \
++ typeof(x) *__xp = &(x); \
++ kcsan_check_atomic_write(__xp, sizeof(*__xp)); \
++ data_race(({ __WRITE_ONCE(*__xp, val); 0; })); \
+} while (0)
+
++#define WRITE_ONCE(x, val) \
++do { \
++ compiletime_assert_rwonce_type(x); \
++ __WRITE_ONCE_SCALAR(x, val); \
+} while (0)
+
#ifdef CONFIG_KASAN
/*
- * We can't declare function 'inline' because __no_sanitize_address confilcts
+ * 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
+ * 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
# define __no_kasan_or_inline __always_inline
#endif
- static __no_kasan_or_inline
+ #define __no_kcsan __no_sanitize_thread
+ #ifdef __SANITIZE_THREAD__
+ /*
+ * Rely on __SANITIZE_THREAD__ instead of CONFIG_KCSAN, to avoid not inlining in
+ * compilation units where instrumentation is disabled. The attribute 'noinline'
+ * is required for older compilers, where implicit inlining of very small
+ * functions renders __no_sanitize_thread ineffective.
+ */
+ # define __no_kcsan_or_inline __no_kcsan noinline notrace __maybe_unused
+ # define __no_sanitize_or_inline __no_kcsan_or_inline
+ #else
+ # define __no_kcsan_or_inline __always_inline
+ #endif
+
+ #ifndef __no_sanitize_or_inline
+ #define __no_sanitize_or_inline __always_inline
+ #endif
+
-static __no_kcsan_or_inline
-void __read_once_size(const volatile void *p, void *res, int size)
-{
- kcsan_check_atomic_read(p, size);
- __READ_ONCE_SIZE;
-}
-
+ static __no_sanitize_or_inline
-void __read_once_size_nocheck(const volatile void *p, void *res, int size)
+unsigned long __read_once_word_nocheck(const void *addr)
{
- __READ_ONCE_SIZE;
-}
-
-static __no_kcsan_or_inline
-void __write_once_size(volatile void *p, void *res, int size)
-{
- kcsan_check_atomic_write(p, 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();
- }
+ return __READ_ONCE(*(unsigned long *)addr);
}
/*
- * 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. 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.
- *
- * 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.
+ * 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.
++ * word from memory atomically but without telling KASAN/KCSAN. This is
++ * usually used by unwinding code when walking the stack of a running process.
*/
-#include <asm/barrier.h>
-#include <linux/kasan-checks.h>
-
-#define __READ_ONCE(x, check) \
+#define READ_ONCE_NOCHECK(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; \
+ 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; \
})
-#define READ_ONCE(x) __READ_ONCE(x, 1)
-
-/*
- * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
- * to hide memory access from KASAN.
- */
-#define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
static __no_kasan_or_inline
unsigned long read_word_at_a_time(const void *addr)
projects / kernel.git / commitdiff