1 files changed, 51 insertions, 0 deletions

diff --git a/include/linux/indirect_call_wrapper.h b/include/linux/indirect_call_wrapper.h
new file mode 100644
index 000000000000..7c8b7f4948af
--- /dev/null
+++ b/include/linux/indirect_call_wrapper.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_INDIRECT_CALL_WRAPPER_H
+#define _LINUX_INDIRECT_CALL_WRAPPER_H
+
+#ifdef CONFIG_RETPOLINE
+
+/*
+ * INDIRECT_CALL_$NR - wrapper for indirect calls with $NR known builtin
+ *  @f: function pointer
+ *  @f$NR: builtin functions names, up to $NR of them
+ *  @__VA_ARGS__: arguments for @f
+ *
+ * Avoid retpoline overhead for known builtin, checking @f vs each of them and
+ * eventually invoking directly the builtin function. The functions are check
+ * in the given order. Fallback to the indirect call.
+ */
+#define INDIRECT_CALL_1(f, f1, ...)                                     \
+        ({                                                              \
+                likely(f == f1) ? f1(__VA_ARGS__) : f(__VA_ARGS__);     \
+        })
+#define INDIRECT_CALL_2(f, f2, f1, ...)                                 \
+        ({                                                              \
+                likely(f == f2) ? f2(__VA_ARGS__) :                     \
+                                  INDIRECT_CALL_1(f, f1, __VA_ARGS__);  \
+        })
+
+#define INDIRECT_CALLABLE_DECLARE(f)    f
+#define INDIRECT_CALLABLE_SCOPE
+
+#else
+#define INDIRECT_CALL_1(f, name, ...) f(__VA_ARGS__)
+#define INDIRECT_CALL_2(f, name, ...) f(__VA_ARGS__)
+#define INDIRECT_CALLABLE_DECLARE(f)
+#define INDIRECT_CALLABLE_SCOPE         static
+#endif
+
+/*
+ * We can use INDIRECT_CALL_$NR for ipv6 related functions only if ipv6 is
+ * builtin, this macro simplify dealing with indirect calls with only ipv4/ipv6
+ * alternatives
+ */
+#if IS_BUILTIN(CONFIG_IPV6)
+#define INDIRECT_CALL_INET(f, f2, f1, ...) \
+        INDIRECT_CALL_2(f, f2, f1, __VA_ARGS__)
+#elif IS_ENABLED(CONFIG_INET)
+#define INDIRECT_CALL_INET(f, f2, f1, ...) INDIRECT_CALL_1(f, f1, __VA_ARGS__)
+#else
+#define INDIRECT_CALL_INET(f, f2, f1, ...) f(__VA_ARGS__)
+#endif
+
+#endif