[PATCH] Add EXPORT_UNUSED_SYMBOL and EXPORT_UNUSED_SYMBOL_GPL

Temporarily add EXPORT_UNUSED_SYMBOL and EXPORT_UNUSED_SYMBOL_GPL.  These
will be used as a transition measure for symbols that aren't used in the
kernel and are on the way out.  When a module uses such a symbol, a warning
is printk'd at modprobe time.

The main reason for removing unused exports is size: eacho export takes
roughly between 100 and 150 bytes of kernel space in the binary.  This
patch gives users the option to immediately get this size gain via a config
option.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 48 insertions, 0 deletions

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 9d11550b4818..db5a3732f106 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -58,6 +58,20 @@
                 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)                                     \
+                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)                                 \
+                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) = .;       \
@@ -79,6 +93,20 @@
                 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)                                     \
+                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)                                 \
+                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) = .;       \
diff --git a/include/linux/module.h b/include/linux/module.h
index 9ebbb74b7b72..9e9dc7c24d95 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -203,6 +203,15 @@ void *__symbol_get_gpl(const char *symbol);
 #define EXPORT_SYMBOL_GPL_FUTURE(sym)                           \
         __EXPORT_SYMBOL(sym, "_gpl_future")
 
+
+#ifdef CONFIG_UNUSED_SYMBOLS
+#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)
+#endif
+
 #endif
 
 struct module_ref
@@ -261,6 +270,15 @@ struct module
         unsigned int num_gpl_syms;
         const unsigned long *gpl_crcs;
 
+        /* unused exported symbols. */
+        const struct kernel_symbol *unused_syms;
+        unsigned int num_unused_syms;
+        const unsigned long *unused_crcs;
+        /* GPL-only, unused exported symbols. */
+        const struct kernel_symbol *unused_gpl_syms;
+        unsigned int num_unused_gpl_syms;
+        const unsigned long *unused_gpl_crcs;
+
         /* symbols that will be GPL-only in the near future. */
         const struct kernel_symbol *gpl_future_syms;
         unsigned int num_gpl_future_syms;
@@ -456,6 +474,8 @@ void module_remove_driver(struct device_driver *);
 #define EXPORT_SYMBOL(sym)
 #define EXPORT_SYMBOL_GPL(sym)
 #define EXPORT_SYMBOL_GPL_FUTURE(sym)
+#define EXPORT_UNUSED_SYMBOL(sym)
+#define EXPORT_UNUSED_SYMBOL_GPL(sym)
 
 /* Given an address, look for it in the exception tables. */
 static inline const struct exception_table_entry *