objtool: Add ANNOTATE_DATA_SPECIAL

In preparation for the objtool klp diff subcommand, add an
ANNOTATE_DATA_SPECIAL macro which annotates special section entries so
that objtool can determine their size and location and extract them
when needed.

Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

include/linux/annotate.h

@@ -8,34 +8,52 @@
 
 #ifndef __ASSEMBLY__
 
-#define __ASM_ANNOTATE(label, type)					\
-	".pushsection .discard.annotate_insn,\"M\",@progbits,8\n\t"	\
+#define __ASM_ANNOTATE(section, label, type)				\
+	".pushsection " section ",\"M\", @progbits, 8\n\t"		\
 	".long " __stringify(label) " - .\n\t"				\
 	".long " __stringify(type) "\n\t"				\
 	".popsection\n\t"
 
+#define ASM_ANNOTATE_LABEL(label, type)					\
+	__ASM_ANNOTATE(".discard.annotate_insn", label, type)
+
 #define ASM_ANNOTATE(type)						\
 	"911:\n\t"							\
-	__ASM_ANNOTATE(911b, type)
+	ASM_ANNOTATE_LABEL(911b, type)
+
+#define ASM_ANNOTATE_DATA(type)						\
+	"912:\n\t"							\
+	__ASM_ANNOTATE(".discard.annotate_data", 912b, type)
 
 #else /* __ASSEMBLY__ */
 
-.macro ANNOTATE type:req
+.macro __ANNOTATE section, type
 .Lhere_\@:
-	.pushsection .discard.annotate_insn,"M",@progbits,8
+	.pushsection \section, "M", @progbits, 8
 	.long	.Lhere_\@ - .
 	.long	\type
 	.popsection
 .endm
 
+.macro ANNOTATE type
+	__ANNOTATE ".discard.annotate_insn", \type
+.endm
+
+.macro ANNOTATE_DATA type
+	__ANNOTATE ".discard.annotate_data", \type
+.endm
+
 #endif /* __ASSEMBLY__ */
 
 #else /* !CONFIG_OBJTOOL */
 #ifndef __ASSEMBLY__
-#define __ASM_ANNOTATE(label, type) ""
+#define ASM_ANNOTATE_LABEL(label, type) ""
 #define ASM_ANNOTATE(type)
+#define ASM_ANNOTATE_DATA(type)
 #else /* __ASSEMBLY__ */
-.macro ANNOTATE type:req
+.macro ANNOTATE type
+.endm
+.macro ANNOTATE_DATA type
 .endm
 #endif /* __ASSEMBLY__ */
 #endif /* !CONFIG_OBJTOOL */
@@ -47,7 +65,7 @@
  * these relocations will never be used for indirect calls.
  */
 #define ANNOTATE_NOENDBR		ASM_ANNOTATE(ANNOTYPE_NOENDBR)
-#define ANNOTATE_NOENDBR_SYM(sym)	asm(__ASM_ANNOTATE(sym, ANNOTYPE_NOENDBR))
+#define ANNOTATE_NOENDBR_SYM(sym)	asm(ASM_ANNOTATE_LABEL(sym, ANNOTYPE_NOENDBR))
 
 /*
  * This should be used immediately before an indirect jump/call. It tells
@@ -58,8 +76,8 @@
 /*
  * See linux/instrumentation.h
  */
-#define ANNOTATE_INSTR_BEGIN(label)	__ASM_ANNOTATE(label, ANNOTYPE_INSTR_BEGIN)
-#define ANNOTATE_INSTR_END(label)	__ASM_ANNOTATE(label, ANNOTYPE_INSTR_END)
+#define ANNOTATE_INSTR_BEGIN(label)	ASM_ANNOTATE_LABEL(label, ANNOTYPE_INSTR_BEGIN)
+#define ANNOTATE_INSTR_END(label)	ASM_ANNOTATE_LABEL(label, ANNOTYPE_INSTR_END)
 /*
  * objtool annotation to ignore the alternatives and only consider the original
  * instruction(s).
@@ -83,7 +101,7 @@
  * terminating, like a noreturn CALL or UD2 when we know they are not -- eg
  * WARN using UD2.
  */
-#define ANNOTATE_REACHABLE(label)	__ASM_ANNOTATE(label, ANNOTYPE_REACHABLE)
+#define ANNOTATE_REACHABLE(label)	ASM_ANNOTATE_LABEL(label, ANNOTYPE_REACHABLE)
 /*
  * This should not be used; it annotates away CFI violations. There are a few
  * valid use cases like kexec handover to the next kernel image, and there is
@@ -92,7 +110,13 @@
  * There are also a few real issues annotated away, like EFI because we can't
  * control the EFI code.
  */
-#define ANNOTATE_NOCFI_SYM(sym)		asm(__ASM_ANNOTATE(sym, ANNOTYPE_NOCFI))
+#define ANNOTATE_NOCFI_SYM(sym)		asm(ASM_ANNOTATE_LABEL(sym, ANNOTYPE_NOCFI))
+
+/*
+ * Annotate a special section entry.  This emables livepatch module generation
+ * to find and extract individual special section entries as needed.
+ */
+#define ANNOTATE_DATA_SPECIAL		ASM_ANNOTATE_DATA(ANNOTYPE_DATA_SPECIAL)
 
 #else /* __ASSEMBLY__ */
 #define ANNOTATE_NOENDBR		ANNOTATE type=ANNOTYPE_NOENDBR
@@ -104,6 +128,7 @@
 #define ANNOTATE_UNRET_BEGIN		ANNOTATE type=ANNOTYPE_UNRET_BEGIN
 #define ANNOTATE_REACHABLE		ANNOTATE type=ANNOTYPE_REACHABLE
 #define ANNOTATE_NOCFI_SYM		ANNOTATE type=ANNOTYPE_NOCFI
+#define ANNOTATE_DATA_SPECIAL		ANNOTATE_DATA type=ANNOTYPE_DATA_SPECIAL
 #endif /* __ASSEMBLY__ */
 
 #endif /* _LINUX_ANNOTATE_H */

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 */

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 */