Merge branch 'objtool/core' of https://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux

This series introduces new objtool features and a klp-build script to
generate livepatch modules using a source .patch as input.

This builds on concepts from the longstanding out-of-tree kpatch [1]
project which began in 2012 and has been used for many years to generate
livepatch modules for production kernels.  However, this is a complete
rewrite which incorporates hard-earned lessons from 12+ years of
maintaining kpatch.

Key improvements compared to kpatch-build:

  - Integrated with objtool: Leverages objtool's existing control-flow
    graph analysis to help detect changed functions.

  - Works on vmlinux.o: Supports late-linked objects, making it
    compatible with LTO, IBT, and similar.

  - Simplified code base: ~3k fewer lines of code.

  - Upstream: No more out-of-tree #ifdef hacks, far less cruft.

  - Cleaner internals: Vastly simplified logic for symbol/section/reloc
    inclusion and special section extraction.

  - Robust __LINE__ macro handling: Avoids false positive binary diffs
    caused by the __LINE__ macro by introducing a fix-patch-lines script
    which injects #line directives into the source .patch to preserve
    the original line numbers at compile time.

The primary user interface is the klp-build script which does the
following:

  - Builds an original kernel with -function-sections and
    -fdata-sections, plus objtool function checksumming.

  - Applies the .patch file and rebuilds the kernel using the same
    options.

  - Runs 'objtool klp diff' to detect changed functions and generate
    intermediate binary diff objects.

  - Builds a kernel module which links the diff objects with some
    livepatch module init code (scripts/livepatch/init.c).

  - Finalizes the livepatch module (aka work around linker wreckage)
    using 'objtool klp post-link'.

I've tested with a variety of patches on defconfig and Fedora-config
kernels with both GCC and Clang.

4 files changed, 95 insertions, 7 deletions

diff --git a/tools/include/linux/interval_tree_generic.h b/tools/include/linux/interval_tree_generic.h
index aaa8a0767aa3..c5a2fed49eb0 100644
--- a/tools/include/linux/interval_tree_generic.h
+++ b/tools/include/linux/interval_tree_generic.h
@@ -77,7 +77,7 @@ ITSTATIC void ITPREFIX ## _remove(ITSTRUCT *node,			      \
  *   Cond2: start <= ITLAST(node)					      \
  */									      \
 									      \
-static ITSTRUCT *							      \
+ITSTATIC ITSTRUCT *							      \
 ITPREFIX ## _subtree_search(ITSTRUCT *node, ITTYPE start, ITTYPE last)	      \
 {									      \
 	while (true) {							      \
@@ -104,12 +104,8 @@ ITPREFIX ## _subtree_search(ITSTRUCT *node, ITTYPE start, ITTYPE last)	      \
 		if (ITSTART(node) <= last) {		/* Cond1 */	      \
 			if (start <= ITLAST(node))	/* Cond2 */	      \
 				return node;	/* node is leftmost match */  \
-			if (node->ITRB.rb_right) {			      \
-				node = rb_entry(node->ITRB.rb_right,	      \
-						ITSTRUCT, ITRB);	      \
-				if (start <= node->ITSUBTREE)		      \
-					continue;			      \
-			}						      \
+			node = rb_entry(node->ITRB.rb_right, ITSTRUCT, ITRB); \
+			continue;					      \
 		}							      \
 		return NULL;	/* No match */				      \
 	}								      \
diff --git a/tools/include/linux/livepatch_external.h b/tools/include/linux/livepatch_external.h
new file mode 100644
index 000000000000..138af19b0f5c
--- /dev/null
+++ b/tools/include/linux/livepatch_external.h
@@ -0,0 +1,76 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * External livepatch interfaces for patch creation tooling
+ */
+
+#ifndef _LINUX_LIVEPATCH_EXTERNAL_H_
+#define _LINUX_LIVEPATCH_EXTERNAL_H_
+
+#include <linux/types.h>
+
+#define KLP_RELOC_SEC_PREFIX		".klp.rela."
+#define KLP_SYM_PREFIX			".klp.sym."
+
+#define __KLP_PRE_PATCH_PREFIX		__klp_pre_patch_callback_
+#define __KLP_POST_PATCH_PREFIX		__klp_post_patch_callback_
+#define __KLP_PRE_UNPATCH_PREFIX	__klp_pre_unpatch_callback_
+#define __KLP_POST_UNPATCH_PREFIX	__klp_post_unpatch_callback_
+
+#define KLP_PRE_PATCH_PREFIX		__stringify(__KLP_PRE_PATCH_PREFIX)
+#define KLP_POST_PATCH_PREFIX		__stringify(__KLP_POST_PATCH_PREFIX)
+#define KLP_PRE_UNPATCH_PREFIX		__stringify(__KLP_PRE_UNPATCH_PREFIX)
+#define KLP_POST_UNPATCH_PREFIX		__stringify(__KLP_POST_UNPATCH_PREFIX)
+
+struct klp_object;
+
+typedef int (*klp_pre_patch_t)(struct klp_object *obj);
+typedef void (*klp_post_patch_t)(struct klp_object *obj);
+typedef void (*klp_pre_unpatch_t)(struct klp_object *obj);
+typedef void (*klp_post_unpatch_t)(struct klp_object *obj);
+
+/**
+ * struct klp_callbacks - pre/post live-(un)patch callback structure
+ * @pre_patch:		executed before code patching
+ * @post_patch:		executed after code patching
+ * @pre_unpatch:	executed before code unpatching
+ * @post_unpatch:	executed after code unpatching
+ * @post_unpatch_enabled:	flag indicating if post-unpatch callback
+ *				should run
+ *
+ * All callbacks are optional.  Only the pre-patch callback, if provided,
+ * will be unconditionally executed.  If the parent klp_object fails to
+ * patch for any reason, including a non-zero error status returned from
+ * the pre-patch callback, no further callbacks will be executed.
+ */
+struct klp_callbacks {
+	klp_pre_patch_t		pre_patch;
+	klp_post_patch_t	post_patch;
+	klp_pre_unpatch_t	pre_unpatch;
+	klp_post_unpatch_t	post_unpatch;
+	bool post_unpatch_enabled;
+};
+
+/*
+ * 'struct klp_{func,object}_ext' are compact "external" representations of
+ * 'struct klp_{func,object}'.   They are used by objtool for livepatch
+ * generation.  The structs are then read by the livepatch module and converted
+ * to the real structs before calling klp_enable_patch().
+ *
+ * TODO make these the official API for klp_enable_patch().  That should
+ * simplify livepatch's interface as well as its data structure lifetime
+ * management.
+ */
+struct klp_func_ext {
+	const char *old_name;
+	void *new_func;
+	unsigned long sympos;
+};
+
+struct klp_object_ext {
+	const char *name;
+	struct klp_func_ext *funcs;
+	struct klp_callbacks callbacks;
+	unsigned int nr_funcs;
+};
+
+#endif /* _LINUX_LIVEPATCH_EXTERNAL_H_ */
diff --git a/tools/include/linux/objtool_types.h b/tools/include/linux/objtool_types.h
index aceac94632c8..c6def4049b1a 100644
--- a/tools/include/linux/objtool_types.h
+++ b/tools/include/linux/objtool_types.h
@@ -67,4 +67,6 @@ struct unwind_hint {
 #define ANNOTYPE_REACHABLE		8
 #define ANNOTYPE_NOCFI			9
 
+#define ANNOTYPE_DATA_SPECIAL		1
+
 #endif /* _LINUX_OBJTOOL_TYPES_H */
diff --git a/tools/include/linux/string.h b/tools/include/linux/string.h
index 8499f509f03e..51ad3cf4fa82 100644
--- a/tools/include/linux/string.h
+++ b/tools/include/linux/string.h
@@ -44,6 +44,20 @@ static inline bool strstarts(const char *str, const char *prefix)
 	return strncmp(str, prefix, strlen(prefix)) == 0;
 }
 
+/*
+ * Checks if a string ends with another.
+ */
+static inline bool str_ends_with(const char *str, const char *substr)
+{
+	size_t len = strlen(str);
+	size_t sublen = strlen(substr);
+
+	if (sublen > len)
+		return false;
+
+	return !strcmp(str + len - sublen, substr);
+}
+
 extern char * __must_check skip_spaces(const char *);
 
 extern char *strim(char *);