1 files changed, 45 insertions, 7 deletions

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 547ea1ff806e..6f1ca49306d2 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -2,6 +2,15 @@
 #ifndef __LINUX_COMPILER_TYPES_H
 #define __LINUX_COMPILER_TYPES_H
 
+/*
+ * __has_builtin is supported on gcc >= 10, clang >= 3 and icc >= 21.
+ * In the meantime, to support gcc < 10, we implement __has_builtin
+ * by hand.
+ */
+#ifndef __has_builtin
+#define __has_builtin(x) (0)
+#endif
+
 #ifndef __ASSEMBLY__
 
 /*
@@ -106,15 +115,32 @@ static inline void __chk_io_ptr(const volatile void __iomem *ptr) { }
 #define __cold
 #endif
 
-/* Builtins */
-
 /*
- * __has_builtin is supported on gcc >= 10, clang >= 3 and icc >= 21.
- * In the meantime, to support gcc < 10, we implement __has_builtin
- * by hand.
+ * On x86-64 and arm64 targets, __preserve_most changes the calling convention
+ * of a function to make the code in the caller as unintrusive as possible. This
+ * convention behaves identically to the C calling convention on how arguments
+ * and return values are passed, but uses a different set of caller- and callee-
+ * saved registers.
+ *
+ * The purpose is to alleviates the burden of saving and recovering a large
+ * register set before and after the call in the caller.  This is beneficial for
+ * rarely taken slow paths, such as error-reporting functions that may be called
+ * from hot paths.
+ *
+ * Note: This may conflict with instrumentation inserted on function entry which
+ * does not use __preserve_most or equivalent convention (if in assembly). Since
+ * function tracing assumes the normal C calling convention, where the attribute
+ * is supported, __preserve_most implies notrace.  It is recommended to restrict
+ * use of the attribute to functions that should or already disable tracing.
+ *
+ * Optional: not supported by gcc.
+ *
+ * clang: https://clang.llvm.org/docs/AttributeReference.html#preserve-most
  */
-#ifndef __has_builtin
-#define __has_builtin(x) (0)
+#if __has_attribute(__preserve_most__) && (defined(CONFIG_X86_64) || defined(CONFIG_ARM64))
+# define __preserve_most notrace __attribute__((__preserve_most__))
+#else
+# define __preserve_most
 #endif
 
 /* Compiler specific macros. */
@@ -324,6 +350,18 @@ struct ftrace_likely_data {
 # define __realloc_size(x, ...)
 #endif
 
+/*
+ * When the size of an allocated object is needed, use the best available
+ * mechanism to find it. (For cases where sizeof() cannot be used.)
+ */
+#if __has_builtin(__builtin_dynamic_object_size)
+#define __struct_size(p)	__builtin_dynamic_object_size(p, 0)
+#define __member_size(p)	__builtin_dynamic_object_size(p, 1)
+#else
+#define __struct_size(p)	__builtin_object_size(p, 0)
+#define __member_size(p)	__builtin_object_size(p, 1)
+#endif
+
 #ifndef asm_volatile_goto
 #define asm_volatile_goto(x...) asm goto(x)
 #endif