[PATCH v4 01/27] linkage: new macros for assembler symbols

[Jiri Slaby]

Introduce new C macros for annotations of functions and data in
assembly. There is a long-standing mess in macros like ENTRY, END,
ENDPROC and similar. They are used in different manners and sometimes
incorrectly.

So introduce macros with clear use to annotate assembly as follows:

a) Support macros for the ones below
   SYM_T_FUNC -- type used by assembler to mark functions
   SYM_T_OBJECT -- type used by assembler to mark data
   SYM_T_NONE -- type used by assembler to mark entries of unknown type

   They are defined as STT_FUNC, STT_OBJECT, and STT_NOTYPE
   respectively. According to the gas manual, this is the most portable
   way. I am not sure about other assemblers, so we can switch this back
   to %function and %object if this turns into a problem. Architectures
   can also override them by something like ", @function" if they need.

   SYM_A_ALIGN, SYM_A_NONE -- align the symbol?
   SYM_V_GLOBAL, SYM_V_WEAK, SYM_V_LOCAL -- visibility of symbols

b) Mostly internal annotations, used by the ones below
   SYM_ENTRY -- use only if you have to (for non-paired symbols)
   SYM_START -- use only if you have to (for paired symbols)
   SYM_END -- use only if you have to (for paired symbols)

c) Annotations for code
   SYM_FUNC_START_LOCAL_ALIAS -- use where there are two local names for
	one function
   SYM_FUNC_START_ALIAS -- use where there are two global names for one
	function
   SYM_FUNC_END_ALIAS -- the end of LOCAL_ALIASed or ALIASed function

   SYM_FUNC_START -- use for global functions
   SYM_FUNC_START_NOALIGN -- use for global functions, w/o alignment
   SYM_FUNC_START_LOCAL -- use for local functions
   SYM_FUNC_START_LOCAL_NOALIGN -- use for local functions, w/o
	alignment
   SYM_FUNC_START_WEAK -- use for weak functions
   SYM_FUNC_START_WEAK_NOALIGN -- use for weak functions, w/o alignment
   SYM_FUNC_END -- the end of SYM_FUNC_START_LOCAL, SYM_FUNC_START,
	SYM_FUNC_START_WEAK, ...

   SYM_FUNC_INNER_LABEL -- only for labels in the middle of functions
   SYM_FUNC_INNER_LABEL_NOALIGN -- only for labels in the middle of
	functions, w/o alignment

   For functions with special (non-C) calling conventions:
   SYM_CODE_START -- use for non-C (special) functions
   SYM_CODE_START_NOALIGN -- use for non-C (special) functions, w/o
	alignment
   SYM_CODE_START_LOCAL -- use for local non-C (special) functions
   SYM_CODE_START_LOCAL_NOALIGN -- use for local non-C (special)
	functions, w/o alignment
   SYM_CODE_END -- the end of SYM_CODE_START_LOCAL or SYM_CODE_START

   SYM_CODE_INNER_LABEL -- only for labels in the middle of code
   SYM_CODE_INNER_LABEL_NOALIGN -- only for labels in the middle of code

d) For data
   SYM_DATA_START -- global data symbol
   SYM_DATA_END -- the end of the SYM_DATA_START symbol
   SYM_DATA_END_LABEL -- the labeled end of SYM_DATA_START symbol
   SYM_DATA_SIMPLE -- start+end wrapper around simple global data
   SYM_DATA_SIMPLE_LOCAL -- start+end wrapper around simple local data

==========

The macros allow to pair starts and ends of functions and mark functions
correctly in the output ELF objects.

All users of the old macros in x86 are converted to use these in further
patches.

[v2]
* use SYM_ prefix and sane names
* add SYM_START and SYM_END and parametrize all the macros

[v3]
* add SYM_DATA_SIMPLE, SYM_DATA_SIMPLE_LOCAL, and SYM_DATA_END_LABEL

[v4]
* add _NOALIGN versions of some macros
* add _CODE_ derivates of _FUNC_ macros

Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: hpa@xxxxxxxxx
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: jpoimboe@xxxxxxxxxx
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Len Brown <len.brown@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-pm@xxxxxxxxxxxxxxx
Cc: mingo@xxxxxxxxxx
Cc: Pavel Machek <pavel@xxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Cc: x86@xxxxxxxxxx
---
 arch/x86/include/asm/linkage.h |  10 +-
 include/linux/linkage.h        | 257 +++++++++++++++++++++++++++++++++++++++--
 2 files changed, 257 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/linkage.h b/arch/x86/include/asm/linkage.h
index 0ccb26dda126..1d22926bb313 100644
--- a/arch/x86/include/asm/linkage.h
+++ b/arch/x86/include/asm/linkage.h
@@ -12,9 +12,13 @@
 
 #ifdef __ASSEMBLY__
 
-#define GLOBAL(name)	\
-	.globl name;	\
-	name:
+/*
+ * GLOBAL is DEPRECATED
+ *
+ * use SYM_DATA_START, SYM_FUNC_START, SYM_FUNC_INNER_LABEL, SYM_CODE_START, or
+ * similar
+ */
+#define GLOBAL(name)	SYM_ENTRY(name, SYM_V_GLOBAL, SYM_A_NONE)
 
 #if defined(CONFIG_X86_64) || defined(CONFIG_X86_ALIGNMENT_16)
 #define __ALIGN		.p2align 4, 0x90
diff --git a/include/linux/linkage.h b/include/linux/linkage.h
index a6a42dd02466..05b5591b5cf7 100644
--- a/include/linux/linkage.h
+++ b/include/linux/linkage.h
@@ -74,25 +74,51 @@
 
 #ifdef __ASSEMBLY__
 
+/* SYM_T_FUNC -- type used by assembler to mark functions */
+#ifndef SYM_T_FUNC
+#define SYM_T_FUNC				STT_FUNC
+#endif
+
+/* SYM_T_OBJECT -- type used by assembler to mark data */
+#ifndef SYM_T_OBJECT
+#define SYM_T_OBJECT				STT_OBJECT
+#endif
+
+/* SYM_T_NONE -- type used by assembler to mark entries of unknown type */
+#ifndef SYM_T_NONE
+#define SYM_T_NONE				STT_NOTYPE
+#endif
+
+/* SYM_A_* -- align the symbol? */
+#define SYM_A_ALIGN				ALIGN
+#define SYM_A_NONE				/* nothing */
+
+/* SYM_V_* -- visibility of symbols */
+#define SYM_V_GLOBAL(name)			.globl name
+#define SYM_V_WEAK(name)			.weak name
+#define SYM_V_LOCAL(name)			/* nothing */
+
 #ifndef LINKER_SCRIPT
 #define ALIGN __ALIGN
 #define ALIGN_STR __ALIGN_STR
 
+/* === DEPRECATED annotations === */
+
 #ifndef ENTRY
+/* deprecated, use SYM_FUNC_START */
 #define ENTRY(name) \
-	.globl name ASM_NL \
-	ALIGN ASM_NL \
-	name:
+	SYM_FUNC_START(name)
 #endif
 #endif /* LINKER_SCRIPT */
 
 #ifndef WEAK
+/* deprecated, use SYM_FUNC_START_WEAK* */
 #define WEAK(name)	   \
-	.weak name ASM_NL   \
-	name:
+	SYM_FUNC_START_WEAK_NOALIGN(name)
 #endif
 
 #ifndef END
+/* deprecated, use SYM_FUNC_END, SYM_DATA_END, or SYM_END */
 #define END(name) \
 	.size name, .-name
 #endif
@@ -102,11 +128,228 @@
  * static analysis tools such as stack depth analyzer.
  */
 #ifndef ENDPROC
+/* deprecated, use SYM_FUNC_END */
 #define ENDPROC(name) \
-	.type name, @function ASM_NL \
-	END(name)
+	SYM_FUNC_END(name)
 #endif
 
+/* === generic annotations === */
+
+/* SYM_ENTRY -- use only if you have to for non-paired symbols */
+#ifndef SYM_ENTRY
+#define SYM_ENTRY(name, visibility, align...)		\
+	visibility(name) ASM_NL				\
+	align ASM_NL					\
+	name:
+#endif
+
+/* SYM_START -- use only if you have to */
+#ifndef SYM_START
+#define SYM_START(name, visibility, align...)		\
+	SYM_ENTRY(name, visibility, align)
 #endif
 
+/* SYM_END -- use only if you have to */
+#ifndef SYM_END
+#define SYM_END(name, sym_type)				\
+	.type name sym_type ASM_NL			\
+	.size name, .-name
 #endif
+
+/* === code annotations === */
+
+/*
+ * FUNC -- C-like functions (proper stack frame etc.)
+ * CODE -- non-C code (e.g. irq handlers with different, special stack etc.)
+ *
+ * Objtool validates stack for FUNC, but not for CODE.
+ * Objtool generates debug info for both FUNC & CODE, but needs special
+ * annotations for each CODE's start (to describe the actual stack frame).
+ *
+ * ALIAS -- does not generate debug info -- the aliased function will
+ */
+
+/*
+ * SYM_FUNC_START_LOCAL_ALIAS -- use where there are two local names for one
+ * function
+ */
+#ifndef SYM_FUNC_START_LOCAL_ALIAS
+#define SYM_FUNC_START_LOCAL_ALIAS(name)		\
+	SYM_START(name, SYM_V_LOCAL, SYM_A_ALIGN)
+#endif
+
+/*
+ * SYM_FUNC_START_ALIAS -- use where there are two global names for one
+ * function
+ */
+#ifndef SYM_FUNC_START_ALIAS
+#define SYM_FUNC_START_ALIAS(name)			\
+	SYM_START(name, SYM_V_GLOBAL, SYM_A_ALIGN)
+#endif
+
+/* SYM_FUNC_START -- use for global functions */
+#ifndef SYM_FUNC_START
+/*
+ * The same as SYM_FUNC_START_ALIAS, but we will need to distinguish these two
+ * later.
+ */
+#define SYM_FUNC_START(name)				\
+	SYM_START(name, SYM_V_GLOBAL, SYM_A_ALIGN)
+#endif
+
+/* SYM_FUNC_START_NOALIGN -- use for global functions, w/o alignment */
+#ifndef SYM_FUNC_START_NOALIGN
+#define SYM_FUNC_START_NOALIGN(name)			\
+	SYM_START(name, SYM_V_GLOBAL, SYM_A_NONE)
+#endif
+
+/* SYM_FUNC_START_LOCAL -- use for local functions */
+#ifndef SYM_FUNC_START_LOCAL
+/* the same as SYM_FUNC_START_LOCAL_ALIAS, see comment near SYM_FUNC_START */
+#define SYM_FUNC_START_LOCAL(name)			\
+	SYM_START(name, SYM_V_LOCAL, SYM_A_ALIGN)
+#endif
+
+/* SYM_FUNC_START_LOCAL_NOALIGN -- use for local functions, w/o alignment */
+#ifndef SYM_FUNC_START_LOCAL_NOALIGN
+#define SYM_FUNC_START_LOCAL_NOALIGN(name)		\
+	SYM_START(name, SYM_V_LOCAL, SYM_A_NONE)
+#endif
+
+/* SYM_FUNC_START_WEAK -- use for weak functions */
+#ifndef SYM_FUNC_START_WEAK
+#define SYM_FUNC_START_WEAK(name)			\
+	SYM_START(name, SYM_V_WEAK, SYM_A_ALIGN)
+#endif
+
+/* SYM_FUNC_START_WEAK_NOALIGN -- use for weak functions, w/o alignment */
+#ifndef SYM_FUNC_START_WEAK_NOALIGN
+#define SYM_FUNC_START_WEAK_NOALIGN(name)		\
+	SYM_START(name, SYM_V_WEAK, SYM_A_NONE)
+#endif
+
+/* SYM_FUNC_END_ALIAS -- the end of LOCAL_ALIASed or ALIASed function */
+#ifndef SYM_FUNC_END_ALIAS
+#define SYM_FUNC_END_ALIAS(name)			\
+	SYM_END(name, SYM_T_FUNC)
+#endif
+
+/*
+ * SYM_FUNC_END -- the end of SYM_FUNC_START_LOCAL, SYM_FUNC_START,
+ * SYM_FUNC_START_WEAK, ...
+ */
+#ifndef SYM_FUNC_END
+/* the same as SYM_FUNC_END_ALIAS, see comment near SYM_FUNC_START */
+#define SYM_FUNC_END(name)				\
+	SYM_END(name, SYM_T_FUNC)
+#endif
+
+/* SYM_FUNC_INNER_LABEL -- only for labels in the middle of functions */
+#ifndef SYM_FUNC_INNER_LABEL
+#define SYM_FUNC_INNER_LABEL(name, visibility)		\
+	.type name SYM_T_FUNC ASM_NL			\
+	SYM_ENTRY(name, visibility, SYM_A_ALIGN)
+#endif
+
+/* SYM_FUNC_INNER_LABEL_NOALIGN -- only for labels in the middle of functions */
+#ifndef SYM_FUNC_INNER_LABEL_NOALIGN
+#define SYM_FUNC_INNER_LABEL_NOALIGN(name, visibility)	\
+	.type name SYM_T_FUNC ASM_NL			\
+	SYM_ENTRY(name, visibility, SYM_A_NONE)
+#endif
+
+/* SYM_CODE_START -- use for non-C (special) functions */
+#ifndef SYM_CODE_START
+#define SYM_CODE_START(name)				\
+	SYM_START(name, SYM_V_GLOBAL, SYM_A_ALIGN)
+#endif
+
+/* SYM_CODE_START_NOALIGN -- use for non-C (special) functions, w/o alignment */
+#ifndef SYM_CODE_START_NOALIGN
+#define SYM_CODE_START_NOALIGN(name)			\
+	SYM_START(name, SYM_V_GLOBAL, SYM_A_NONE)
+#endif
+
+/* SYM_CODE_START_LOCAL -- use for local non-C (special) functions */
+#ifndef SYM_CODE_START_LOCAL
+#define SYM_CODE_START_LOCAL(name)			\
+	SYM_START(name, SYM_V_LOCAL, SYM_A_ALIGN)
+#endif
+
+/*
+ * SYM_CODE_START_LOCAL_NOALIGN -- use for local non-C (special) functions,
+ * w/o alignment
+ */
+#ifndef SYM_CODE_START_LOCAL_NOALIGN
+#define SYM_CODE_START_LOCAL_NOALIGN(name)		\
+	SYM_START(name, SYM_V_LOCAL, SYM_A_NONE)
+#endif
+
+/* SYM_CODE_END -- the end of SYM_CODE_START_LOCAL, SYM_CODE_START, ... */
+#ifndef SYM_CODE_END
+#define SYM_CODE_END(name)				\
+	SYM_END(name, SYM_T_NONE)
+#endif
+
+/* SYM_CODE_INNER_LABEL -- only for labels in the middle of code */
+#ifndef SYM_CODE_INNER_LABEL
+#define SYM_CODE_INNER_LABEL(name, visibility)		\
+	.type name SYM_T_NONE ASM_NL			\
+	SYM_ENTRY(name, visibility, SYM_A_ALIGN)
+#endif
+
+/* SYM_CODE_INNER_LABEL_NOALIGN -- only for labels in the middle of code */
+#ifndef SYM_CODE_INNER_LABEL_NOALIGN
+#define SYM_CODE_INNER_LABEL_NOALIGN(name, visibility)	\
+	.type name SYM_T_NONE ASM_NL			\
+	SYM_ENTRY(name, visibility, SYM_A_NONE)
+#endif
+
+/* === data annotations === */
+
+/* SYM_DATA_START -- global data symbol */
+#ifndef SYM_DATA_START
+#define SYM_DATA_START(name)				\
+	SYM_START(name, SYM_V_GLOBAL, SYM_A_NONE)
+#endif
+
+/* SYM_DATA_START -- local data symbol */
+#ifndef SYM_DATA_START_LOCAL
+#define SYM_DATA_START_LOCAL(name)			\
+	SYM_START(name, SYM_V_LOCAL, SYM_A_NONE)
+#endif
+
+/* SYM_DATA_END -- the end of SYM_DATA_START symbol */
+#ifndef SYM_DATA_END
+#define SYM_DATA_END(name)				\
+	SYM_END(name, SYM_T_OBJECT)
+#endif
+
+/* SYM_DATA_END_LABEL -- the labeled end of SYM_DATA_START symbol */
+#ifndef SYM_DATA_END_LABEL
+#define SYM_DATA_END_LABEL(name, visibility, label)	\
+	visibility(label) ASM_NL			\
+	.type label SYM_T_OBJECT ASM_NL			\
+	label:						\
+	SYM_END(name, SYM_T_OBJECT)
+#endif
+
+/* SYM_DATA_SIMPLE -- start+end wrapper around simple global data */
+#ifndef SYM_DATA_SIMPLE
+#define SYM_DATA_SIMPLE(name, data)				\
+	SYM_DATA_START(name) ASM_NL				\
+	data ASM_NL						\
+	SYM_DATA_END(name)
+#endif
+
+/* SYM_DATA_SIMPLE_LOCAL -- start+end wrapper around simple local data */
+#ifndef SYM_DATA_SIMPLE_LOCAL
+#define SYM_DATA_SIMPLE_LOCAL(name, data...)			\
+	SYM_DATA_START_LOCAL(name) ASM_NL			\
+	data ASM_NL						\
+	SYM_DATA_END(name)
+#endif
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* _LINUX_LINKAGE_H */
-- 
2.14.2