export: avoid code duplication in include/linux/export.h

include/linux/export.h has lots of code duplication between
EXPORT_SYMBOL and EXPORT_SYMBOL_NS.

To improve the maintainability and readability, unify the
implementation.

When the symbol has no namespace, pass the empty string "" to
the 'ns' parameter.

The drawback of this change is, it grows the code size.
When the symbol has no namespace, sym->namespace was previously
NULL, but it is now an empty string "". So, it increases 1 byte
for every no namespace EXPORT_SYMBOL.

A typical kernel configuration has 10K exported symbols, so it
increases 10KB in rough estimation.

I did not come up with a good idea to refactor it without increasing
the code size.

I am not sure how big a deal it is, but at least include/linux/export.h
looks nicer.
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
[maennich: rebase on top of 3 fixes for the namespace feature]
Signed-off-by: Matthias Maennich <maennich@google.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>

include/linux/export.h

@@ -46,7 +46,7 @@ extern struct module __this_module;
  * absolute relocations that require runtime processing on relocatable
  * kernels.
  */
-#define __KSYMTAB_ENTRY_NS(sym, sec)					\
+#define __KSYMTAB_ENTRY(sym, sec)					\
 	__ADDRESSABLE(sym)						\
 	asm("	.section \"___ksymtab" sec "+" #sym "\", \"a\"	\n"	\
 	    "	.balign	4					\n"	\
@@ -56,33 +56,17 @@ extern struct module __this_module;
 	    "	.long	__kstrtabns_" #sym "- .			\n"	\
 	    "	.previous					\n")
 
-#define __KSYMTAB_ENTRY(sym, sec)					\
-	__ADDRESSABLE(sym)						\
-	asm("	.section \"___ksymtab" sec "+" #sym "\", \"a\"	\n"	\
-	    "	.balign 4					\n"	\
-	    "__ksymtab_" #sym ":				\n"	\
-	    "	.long	" #sym "- .				\n"	\
-	    "	.long	__kstrtab_" #sym "- .			\n"	\
-	    "	.long	0					\n"	\
-	    "	.previous					\n")
-
 struct kernel_symbol {
 	int value_offset;
 	int name_offset;
 	int namespace_offset;
 };
 #else
-#define __KSYMTAB_ENTRY_NS(sym, sec)					\
-	static const struct kernel_symbol __ksymtab_##sym		\
-	__attribute__((section("___ksymtab" sec "+" #sym), used))	\
-	__aligned(sizeof(void *))					\
-	= { (unsigned long)&sym, __kstrtab_##sym, __kstrtabns_##sym }
-
 #define __KSYMTAB_ENTRY(sym, sec)					\
 	static const struct kernel_symbol __ksymtab_##sym		\
 	__attribute__((section("___ksymtab" sec "+" #sym), used))	\
 	__aligned(sizeof(void *))					\
-	= { (unsigned long)&sym, __kstrtab_##sym, NULL }
+	= { (unsigned long)&sym, __kstrtab_##sym, __kstrtabns_##sym }
 
 struct kernel_symbol {
 	unsigned long value;
@@ -93,28 +77,20 @@ struct kernel_symbol {
 
 #ifdef __GENKSYMS__
 
-#define ___EXPORT_SYMBOL(sym,sec)	__GENKSYMS_EXPORT_SYMBOL(sym)
-#define ___EXPORT_SYMBOL_NS(sym,sec,ns)	__GENKSYMS_EXPORT_SYMBOL(sym)
+#define ___EXPORT_SYMBOL(sym, sec, ns)	__GENKSYMS_EXPORT_SYMBOL(sym)
 
 #else
 
-#define ___export_symbol_common(sym, sec)				\
+/* For every exported symbol, place a struct in the __ksymtab section */
+#define ___EXPORT_SYMBOL(sym, sec, ns)					\
 	extern typeof(sym) sym;						\
 	__CRC_SYMBOL(sym, sec);						\
 	static const char __kstrtab_##sym[]				\
 	__attribute__((section("__ksymtab_strings"), used, aligned(1)))	\
-	= #sym								\
-
-/* For every exported symbol, place a struct in the __ksymtab section */
-#define ___EXPORT_SYMBOL_NS(sym, sec, ns)				\
-	___export_symbol_common(sym, sec);				\
+	= #sym;								\
 	static const char __kstrtabns_##sym[]				\
 	__attribute__((section("__ksymtab_strings"), used, aligned(1)))	\
-	= #ns;								\
-	__KSYMTAB_ENTRY_NS(sym, sec)
-
-#define ___EXPORT_SYMBOL(sym, sec)					\
-	___export_symbol_common(sym, sec);				\
+	= ns;								\
 	__KSYMTAB_ENTRY(sym, sec)
 
 #endif
@@ -126,8 +102,7 @@ struct kernel_symbol {
  * be reused in other execution contexts such as the UEFI stub or the
  * decompressor.
  */
-#define __EXPORT_SYMBOL_NS(sym, sec, ns)
-#define __EXPORT_SYMBOL(sym, sec)
+#define __EXPORT_SYMBOL(sym, sec, ns)
 
 #elif defined(CONFIG_TRIM_UNUSED_KSYMS)
 
@@ -143,48 +118,38 @@ struct kernel_symbol {
 #define __ksym_marker(sym)	\
 	static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
 
-#define __EXPORT_SYMBOL(sym, sec)				\
-	__ksym_marker(sym);					\
-	__cond_export_sym(sym, sec, __is_defined(__KSYM_##sym))
-#define __cond_export_sym(sym, sec, conf)			\
-	___cond_export_sym(sym, sec, conf)
-#define ___cond_export_sym(sym, sec, enabled)			\
-	__cond_export_sym_##enabled(sym, sec)
-#define __cond_export_sym_1(sym, sec) ___EXPORT_SYMBOL(sym, sec)
-#define __cond_export_sym_0(sym, sec) /* nothing */
-
-#define __EXPORT_SYMBOL_NS(sym, sec, ns)				\
+#define __EXPORT_SYMBOL(sym, sec, ns)					\
 	__ksym_marker(sym);						\
-	__cond_export_ns_sym(sym, sec, ns, __is_defined(__KSYM_##sym))
-#define __cond_export_ns_sym(sym, sec, ns, conf)			\
-	___cond_export_ns_sym(sym, sec, ns, conf)
-#define ___cond_export_ns_sym(sym, sec, ns, enabled)			\
-	__cond_export_ns_sym_##enabled(sym, sec, ns)
-#define __cond_export_ns_sym_1(sym, sec, ns) ___EXPORT_SYMBOL_NS(sym, sec, ns)
-#define __cond_export_ns_sym_0(sym, sec, ns) /* nothing */
+	__cond_export_sym(sym, sec, ns, __is_defined(__KSYM_##sym))
+#define __cond_export_sym(sym, sec, ns, conf)				\
+	___cond_export_sym(sym, sec, ns, conf)
+#define ___cond_export_sym(sym, sec, ns, enabled)			\
+	__cond_export_sym_##enabled(sym, sec, ns)
+#define __cond_export_sym_1(sym, sec, ns) ___EXPORT_SYMBOL(sym, sec, ns)
+#define __cond_export_sym_0(sym, sec, ns) /* nothing */
 
 #else
 
-#define __EXPORT_SYMBOL_NS(sym,sec,ns)	___EXPORT_SYMBOL_NS(sym,sec,ns)
-#define __EXPORT_SYMBOL(sym,sec)	___EXPORT_SYMBOL(sym,sec)
+#define __EXPORT_SYMBOL(sym, sec, ns)	___EXPORT_SYMBOL(sym, sec, ns)
 
 #endif /* CONFIG_MODULES */
 
 #ifdef DEFAULT_SYMBOL_NAMESPACE
-#undef __EXPORT_SYMBOL
-#define __EXPORT_SYMBOL(sym, sec)				\
-	__EXPORT_SYMBOL_NS(sym, sec, DEFAULT_SYMBOL_NAMESPACE)
+#include <linux/stringify.h>
+#define _EXPORT_SYMBOL(sym, sec)	__EXPORT_SYMBOL(sym, sec, __stringify(DEFAULT_SYMBOL_NAMESPACE))
+#else
+#define _EXPORT_SYMBOL(sym, sec)	__EXPORT_SYMBOL(sym, sec, "")
 #endif
 
-#define EXPORT_SYMBOL(sym)		__EXPORT_SYMBOL(sym, "")
-#define EXPORT_SYMBOL_GPL(sym)		__EXPORT_SYMBOL(sym, "_gpl")
-#define EXPORT_SYMBOL_GPL_FUTURE(sym)	__EXPORT_SYMBOL(sym, "_gpl_future")
-#define EXPORT_SYMBOL_NS(sym, ns)	__EXPORT_SYMBOL_NS(sym, "", ns)
-#define EXPORT_SYMBOL_NS_GPL(sym, ns)	__EXPORT_SYMBOL_NS(sym, "_gpl", ns)
+#define EXPORT_SYMBOL(sym)		_EXPORT_SYMBOL(sym, "")
+#define EXPORT_SYMBOL_GPL(sym)		_EXPORT_SYMBOL(sym, "_gpl")
+#define EXPORT_SYMBOL_GPL_FUTURE(sym)	_EXPORT_SYMBOL(sym, "_gpl_future")
+#define EXPORT_SYMBOL_NS(sym, ns)	__EXPORT_SYMBOL(sym, "", #ns)
+#define EXPORT_SYMBOL_NS_GPL(sym, ns)	__EXPORT_SYMBOL(sym, "_gpl", #ns)
 
 #ifdef CONFIG_UNUSED_SYMBOLS
-#define EXPORT_UNUSED_SYMBOL(sym)	__EXPORT_SYMBOL(sym, "_unused")
-#define EXPORT_UNUSED_SYMBOL_GPL(sym)	__EXPORT_SYMBOL(sym, "_unused_gpl")
+#define EXPORT_UNUSED_SYMBOL(sym)	_EXPORT_SYMBOL(sym, "_unused")
+#define EXPORT_UNUSED_SYMBOL_GPL(sym)	_EXPORT_SYMBOL(sym, "_unused_gpl")
 #else
 #define EXPORT_UNUSED_SYMBOL(sym)
 #define EXPORT_UNUSED_SYMBOL_GPL(sym)

kernel/module.c

@@ -1400,7 +1400,7 @@ static int verify_namespace_is_imported(const struct load_info *info,
 	char *imported_namespace;
 
 	namespace = kernel_symbol_namespace(sym);
-	if (namespace) {
+	if (namespace && namespace[0]) {
 		imported_namespace = get_modinfo(info, "import_ns");
 		while (imported_namespace) {
 			if (strcmp(namespace, imported_namespace) == 0)