[PATCH v3 64/64] livepatch: Introduce source code helpers for livepatch modules

[Josh Poimboeuf <jpoimboe@kernel.org>]

Add some helper macros which can be used by livepatch source .patch
files to register callbacks, convert static calls to regular calls where
needed, and patch syscalls.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 include/linux/livepatch_helpers.h | 79 +++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)
 create mode 100644 include/linux/livepatch_helpers.h

diff --git a/include/linux/livepatch_helpers.h b/include/linux/livepatch_helpers.h
new file mode 100644
index 000000000000..337bee91d7da
--- /dev/null
+++ b/include/linux/livepatch_helpers.h
@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_LIVEPATCH_HELPERS_H
+#define _LINUX_LIVEPATCH_HELPERS_H
+
+/*
+ * Interfaces for use by livepatch patches
+ */
+
+#include <linux/syscalls.h>
+#include <linux/livepatch.h>
+
+#ifdef MODULE
+#define KLP_OBJNAME __KBUILD_MODNAME
+#else
+#define KLP_OBJNAME vmlinux
+#endif
+
+/* Livepatch callback registration */
+
+#define KLP_CALLBACK_PTRS ".discard.klp_callback_ptrs"
+
+#define KLP_PRE_PATCH_CALLBACK(func)						\
+	klp_pre_patch_t __used __section(KLP_CALLBACK_PTRS)			\
+		__PASTE(__KLP_PRE_PATCH_PREFIX, KLP_OBJNAME) = func
+
+#define KLP_POST_PATCH_CALLBACK(func)						\
+	klp_post_patch_t __used __section(KLP_CALLBACK_PTRS)			\
+		__PASTE(__KLP_POST_PATCH_PREFIX, KLP_OBJNAME) = func
+
+#define KLP_PRE_UNPATCH_CALLBACK(func)						\
+	klp_pre_unpatch_t __used __section(KLP_CALLBACK_PTRS)			\
+		__PASTE(__KLP_PRE_UNPATCH_PREFIX, KLP_OBJNAME) = func
+
+#define KLP_POST_UNPATCH_CALLBACK(func)						\
+	klp_post_unpatch_t __used __section(KLP_CALLBACK_PTRS)			\
+		__PASTE(__KLP_POST_UNPATCH_PREFIX, KLP_OBJNAME) = func
+
+/*
+ * KLP_STATIC_CALL
+ *
+ * Replace static_call() usage with this macro when create-diff-object
+ * recommends it due to the original static call key living in a module.
+ *
+ * This converts the static call to a regular indirect call.
+ */
+#define KLP_STATIC_CALL(name) \
+	((typeof(STATIC_CALL_TRAMP(name))*)(STATIC_CALL_KEY(name).func))
+
+/* Syscall patching */
+
+#define KLP_SYSCALL_DEFINE1(name, ...) KLP_SYSCALL_DEFINEx(1, _##name, __VA_ARGS__)
+#define KLP_SYSCALL_DEFINE2(name, ...) KLP_SYSCALL_DEFINEx(2, _##name, __VA_ARGS__)
+#define KLP_SYSCALL_DEFINE3(name, ...) KLP_SYSCALL_DEFINEx(3, _##name, __VA_ARGS__)
+#define KLP_SYSCALL_DEFINE4(name, ...) KLP_SYSCALL_DEFINEx(4, _##name, __VA_ARGS__)
+#define KLP_SYSCALL_DEFINE5(name, ...) KLP_SYSCALL_DEFINEx(5, _##name, __VA_ARGS__)
+#define KLP_SYSCALL_DEFINE6(name, ...) KLP_SYSCALL_DEFINEx(6, _##name, __VA_ARGS__)
+
+#define KLP_SYSCALL_DEFINEx(x, sname, ...)				\
+	__KLP_SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
+
+#ifdef CONFIG_X86_64
+// TODO move this to arch/x86/include/asm/syscall_wrapper.h and share code
+#define __KLP_SYSCALL_DEFINEx(x, name, ...)			\
+	static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));	\
+	static inline long __klp_do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
+	__X64_SYS_STUBx(x, name, __VA_ARGS__)				\
+	__IA32_SYS_STUBx(x, name, __VA_ARGS__)				\
+	static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))	\
+	{								\
+		long ret = __klp_do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));\
+		__MAP(x,__SC_TEST,__VA_ARGS__);				\
+		__PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__));	\
+		return ret;						\
+	}								\
+	static inline long __klp_do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
+
+#endif
+
+#endif /* _LINUX_LIVEPATCH_HELPERS_H */
-- 
2.49.0