Merge remote-tracking branch 's390/features'

[karo-tx-linux.git] / include / linux / compiler.h

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 449cb674c7fa0046851a1de87624b169348d4c1c..52a459ff75f4c2b88a8083338a2d173ce502f279 100644 (file)
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -198,19 +198,45 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
 
 #include <uapi/linux/types.h>
 
-static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
+#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)
 {
-       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();
-       }
+       __READ_ONCE_SIZE;
+}
+
+#ifdef CONFIG_KASAN
+/*
+ * This function is not '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.
+ */
+static __no_sanitize_address __maybe_unused
+void __read_once_size_nocheck(const volatile void *p, void *res, int size)
+{
+       __READ_ONCE_SIZE;
+}
+#else
+static __always_inline
+void __read_once_size_nocheck(const volatile void *p, void *res, int size)
+{
+       __READ_ONCE_SIZE;
 }
+#endif
 
 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
 {
@@ -248,8 +274,22 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
  * required ordering.
  */
 
-#define READ_ONCE(x) \
-       ({ union { typeof(x) __val; char __c[1]; } __u; __read_once_size(&(x), __u.__c, sizeof(x)); __u.__val; })
+#define __READ_ONCE(x, check)                                          \
+({                                                                     \
+       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));     \
+       __u.__val;                                                      \
+})
+#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)
 
 #define WRITE_ONCE(x, val) \
 ({                                                     \
@@ -259,22 +299,6 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
        __u.__val;                                      \
 })
 
-/**
- * READ_ONCE_CTRL - Read a value heading a control dependency
- * @x: The value to be read, heading the control dependency
- *
- * Control dependencies are tricky.  See Documentation/memory-barriers.txt
- * for important information on how to use them.  Note that in many cases,
- * use of smp_load_acquire() will be much simpler.  Control dependencies
- * should be avoided except on the hottest of hotpaths.
- */
-#define READ_ONCE_CTRL(x) \
-({ \
-       typeof(x) __val = READ_ONCE(x); \
-       smp_read_barrier_depends(); /* Enforce control dependency. */ \
-       __val; \
-})
-
 #endif /* __KERNEL__ */
 
 #endif /* __ASSEMBLY__ */