module: Sort exported symbols

This patch places every exported symbol in its own section
(i.e. "___ksymtab+printk").  Thus the linker will use its SORT() directive
to sort and finally merge all symbol in the right and final section
(i.e. "__ksymtab").

The symbol prefixed archs use an underscore as prefix for symbols.
To avoid collision we use a different character to create the temporary
section names.

This work was supported by a hardware donation from the CE Linux Forum.

Signed-off-by: Alessio Igor Bogani <abogani@kernel.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (folded in '+' fixup)
Tested-by: Dirk Behme <dirk.behme@googlemail.com>

3 files changed, 23 insertions, 12 deletions

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index bd297a20ab9..b27445e00b6 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -274,70 +274,70 @@
 	/* Kernel symbol table: Normal symbols */			\
 	__ksymtab         : AT(ADDR(__ksymtab) - LOAD_OFFSET) {		\
 		VMLINUX_SYMBOL(__start___ksymtab) = .;			\
-		*(__ksymtab)						\
+		*(SORT(___ksymtab+*))					\
 		VMLINUX_SYMBOL(__stop___ksymtab) = .;			\
 	}								\
 									\
 	/* Kernel symbol table: GPL-only symbols */			\
 	__ksymtab_gpl     : AT(ADDR(__ksymtab_gpl) - LOAD_OFFSET) {	\
 		VMLINUX_SYMBOL(__start___ksymtab_gpl) = .;		\
-		*(__ksymtab_gpl)					\
+		*(SORT(___ksymtab_gpl+*))				\
 		VMLINUX_SYMBOL(__stop___ksymtab_gpl) = .;		\
 	}								\
 									\
 	/* Kernel symbol table: Normal unused symbols */		\
 	__ksymtab_unused  : AT(ADDR(__ksymtab_unused) - LOAD_OFFSET) {	\
 		VMLINUX_SYMBOL(__start___ksymtab_unused) = .;		\
-		*(__ksymtab_unused)					\
+		*(SORT(___ksymtab_unused+*))				\
 		VMLINUX_SYMBOL(__stop___ksymtab_unused) = .;		\
 	}								\
 									\
 	/* Kernel symbol table: GPL-only unused symbols */		\
 	__ksymtab_unused_gpl : AT(ADDR(__ksymtab_unused_gpl) - LOAD_OFFSET) { \
 		VMLINUX_SYMBOL(__start___ksymtab_unused_gpl) = .;	\
-		*(__ksymtab_unused_gpl)					\
+		*(SORT(___ksymtab_unused_gpl+*))			\
 		VMLINUX_SYMBOL(__stop___ksymtab_unused_gpl) = .;	\
 	}								\
 									\
 	/* Kernel symbol table: GPL-future-only symbols */		\
 	__ksymtab_gpl_future : AT(ADDR(__ksymtab_gpl_future) - LOAD_OFFSET) { \
 		VMLINUX_SYMBOL(__start___ksymtab_gpl_future) = .;	\
-		*(__ksymtab_gpl_future)					\
+		*(SORT(___ksymtab_gpl_future+*))			\
 		VMLINUX_SYMBOL(__stop___ksymtab_gpl_future) = .;	\
 	}								\
 									\
 	/* Kernel symbol table: Normal symbols */			\
 	__kcrctab         : AT(ADDR(__kcrctab) - LOAD_OFFSET) {		\
 		VMLINUX_SYMBOL(__start___kcrctab) = .;			\
-		*(__kcrctab)						\
+		*(SORT(___kcrctab+*))					\
 		VMLINUX_SYMBOL(__stop___kcrctab) = .;			\
 	}								\
 									\
 	/* Kernel symbol table: GPL-only symbols */			\
 	__kcrctab_gpl     : AT(ADDR(__kcrctab_gpl) - LOAD_OFFSET) {	\
 		VMLINUX_SYMBOL(__start___kcrctab_gpl) = .;		\
-		*(__kcrctab_gpl)					\
+		*(SORT(___kcrctab_gpl+*))				\
 		VMLINUX_SYMBOL(__stop___kcrctab_gpl) = .;		\
 	}								\
 									\
 	/* Kernel symbol table: Normal unused symbols */		\
 	__kcrctab_unused  : AT(ADDR(__kcrctab_unused) - LOAD_OFFSET) {	\
 		VMLINUX_SYMBOL(__start___kcrctab_unused) = .;		\
-		*(__kcrctab_unused)					\
+		*(SORT(___kcrctab_unused+*))				\
 		VMLINUX_SYMBOL(__stop___kcrctab_unused) = .;		\
 	}								\
 									\
 	/* Kernel symbol table: GPL-only unused symbols */		\
 	__kcrctab_unused_gpl : AT(ADDR(__kcrctab_unused_gpl) - LOAD_OFFSET) { \
 		VMLINUX_SYMBOL(__start___kcrctab_unused_gpl) = .;	\
-		*(__kcrctab_unused_gpl)					\
+		*(SORT(___kcrctab_unused_gpl+*))			\
 		VMLINUX_SYMBOL(__stop___kcrctab_unused_gpl) = .;	\
 	}								\
 									\
 	/* Kernel symbol table: GPL-future-only symbols */		\
 	__kcrctab_gpl_future : AT(ADDR(__kcrctab_gpl_future) - LOAD_OFFSET) { \
 		VMLINUX_SYMBOL(__start___kcrctab_gpl_future) = .;	\
-		*(__kcrctab_gpl_future)					\
+		*(SORT(___kcrctab_gpl_future+*))			\
 		VMLINUX_SYMBOL(__stop___kcrctab_gpl_future) = .;	\
 	}								\
 									\
diff --git a/include/linux/module.h b/include/linux/module.h
index 49f4ad0ddec..d9ca2d5dc6d 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -224,7 +224,7 @@ struct module_use {
 	extern void *__crc_##sym __attribute__((weak));		\
 	static const unsigned long __kcrctab_##sym		\
 	__used							\
-	__attribute__((section("__kcrctab" sec), unused))	\
+	__attribute__((section("___kcrctab" sec "+" #sym), unused))	\
 	= (unsigned long) &__crc_##sym;
 #else
 #define __CRC_SYMBOL(sym, sec)
@@ -239,7 +239,7 @@ struct module_use {
 	= MODULE_SYMBOL_PREFIX #sym;                    	\
 	static const struct kernel_symbol __ksymtab_##sym	\
 	__used							\
-	__attribute__((section("__ksymtab" sec), unused))	\
+	__attribute__((section("___ksymtab" sec "+" #sym), unused))	\
 	= { (unsigned long)&sym, __kstrtab_##sym }
 
 #define EXPORT_SYMBOL(sym)					\
diff --git a/scripts/module-common.lds b/scripts/module-common.lds
index 47a1f9ae0ed..0865b3e752b 100644
--- a/scripts/module-common.lds
+++ b/scripts/module-common.lds
@@ -5,4 +5,15 @@
  */
 SECTIONS {
 	/DISCARD/ : { *(.discard) }
+
+	__ksymtab		: { *(SORT(___ksymtab+*)) }
+	__ksymtab_gpl		: { *(SORT(___ksymtab_gpl+*)) }
+	__ksymtab_unused	: { *(SORT(___ksymtab_unused+*)) }
+	__ksymtab_unused_gpl	: { *(SORT(___ksymtab_unused_gpl+*)) }
+	__ksymtab_gpl_future	: { *(SORT(___ksymtab_gpl_future+*)) }
+	__kcrctab		: { *(SORT(___kcrctab+*)) }
+	__kcrctab_gpl		: { *(SORT(___kcrctab_gpl+*)) }
+	__kcrctab_unused	: { *(SORT(___kcrctab_unused+*)) }
+	__kcrctab_unused_gpl	: { *(SORT(___kcrctab_unused_gpl+*)) }
+	__kcrctab_gpl_future	: { *(SORT(___kcrctab_gpl_future+*)) }
 }