add an optional config option for stripping all unnecessary symbol exports from the...
authorFelix Fietkau <nbd@openwrt.org>
Sat, 8 Aug 2009 14:22:04 +0000 (14:22 +0000)
committerFelix Fietkau <nbd@openwrt.org>
Sat, 8 Aug 2009 14:22:04 +0000 (14:22 +0000)
SVN-Revision: 17181

Config.in
include/kernel-build.mk
include/kernel-defaults.mk
target/linux/generic-2.6/patches-2.6.28/027-module_exports.patch [new file with mode: 0644]
target/linux/generic-2.6/patches-2.6.30/028-module_exports.patch [new file with mode: 0644]

index 9879c7d..4076479 100644 (file)
--- a/Config.in
+++ b/Config.in
@@ -134,6 +134,14 @@ config USE_MKLIBS
          Note that this will make the system libraries incompatible with most of the packages
          that are not selected during the build process
 
+config STRIP_KERNEL_EXPORTS
+       depends LINUX_2_6
+       bool "Strip unnecessary exports from the kernel image"
+       help
+         Reduces kernel size by stripping unused kernel exports from the kernel image
+         Note that this might make the kernel incompatible with any kernel modules that
+         were not selected at the time the kernel image was created
+
 comment "Package build options"
 
 config DEBUG
index d48f8b9..e3e446b 100644 (file)
@@ -54,6 +54,28 @@ define BuildKernel
        $(Kernel/Prepare)
        touch $$@
 
+  $(KERNEL_BUILD_DIR)/symtab.txt: FORCE
+       find $(LINUX_DIR) $(STAGING_DIR_ROOT)/lib/modules -name \*.ko | \
+               xargs $(TARGET_CROSS)nm | \
+               awk '$$$$1 == "U" { print $$$$2 } ' | \
+               sort -u > $$@
+
+  $(KERNEL_BUILD_DIR)/symtab.h: $(KERNEL_BUILD_DIR)/symtab.txt
+       ( \
+               echo '#define SYMTAB_KEEP \'; \
+               cat $(KERNEL_BUILD_DIR)/symtab.txt | \
+                       awk '{print "*(__ksymtab." $$$$1 ") \\" }'; \
+               echo; \
+               echo '#define SYMTAB_KEEP_GPL \'; \
+               cat $(KERNEL_BUILD_DIR)/symtab.txt | \
+                       awk '{print "*(__ksymtab_gpl." $$$$1 ") \\" }'; \
+               echo; \
+               echo '#define SYMTAB_KEEP_STR \'; \
+               cat $(KERNEL_BUILD_DIR)/symtab.txt | \
+                       awk '{print "*(__ksymtab_strings." $$$$1 ") \\" }'; \
+               echo; \
+       ) > $$@
+
   $(STAMP_CONFIGURED): $(STAMP_PREPARED) $(LINUX_CONFIG) $(GENERIC_LINUX_CONFIG) $(TOPDIR)/.config
        $(Kernel/Configure)
        touch $$@
@@ -62,7 +84,7 @@ define BuildKernel
        $(Kernel/CompileModules)
        touch $$@
 
-  $(LINUX_DIR)/.image: $(STAMP_CONFIGURED) FORCE
+  $(LINUX_DIR)/.image: $(STAMP_CONFIGURED) $(if $(CONFIG_STRIP_KERNEL_EXPORTS),$(KERNEL_BUILD_DIR)/symtab.h) FORCE
        $(Kernel/CompileImage)
        touch $$@
        
index f205553..0ba1e05 100644 (file)
@@ -22,6 +22,11 @@ KERNEL_MAKEOPTS := -C $(LINUX_DIR) \
        KBUILD_HAVE_NLS=no \
        CONFIG_SHELL="$(BASH)"
 
+ifdef CONFIG_STRIP_KERNEL_EXPORTS
+  KERNEL_MAKEOPTS += \
+       EXTRA_LDSFLAGS="-I$(KERNEL_BUILD_DIR) -include symtab.h"
+endif
+
 INITRAMFS_EXTRA_FILES ?= $(GENERIC_PLATFORM_DIR)/image/initramfs-base-files.txt
 
 ifneq (,$(KERNEL_CC))
diff --git a/target/linux/generic-2.6/patches-2.6.28/027-module_exports.patch b/target/linux/generic-2.6/patches-2.6.28/027-module_exports.patch
new file mode 100644 (file)
index 0000000..2a44832
--- /dev/null
@@ -0,0 +1,117 @@
+--- a/Makefile
++++ b/Makefile
+@@ -963,7 +963,7 @@ prepare: prepare0
+ # Leave this as default for preprocessing vmlinux.lds.S, which is now
+ # done in arch/$(ARCH)/kernel/Makefile
+-export CPPFLAGS_vmlinux.lds += -P -C -U$(ARCH)
++export CPPFLAGS_vmlinux.lds += -P -C -U$(ARCH) $(EXTRA_LDSFLAGS)
+ # The asm symlink changes when $(ARCH) changes.
+ # Detect this and ask user to run make mrproper
+--- a/include/asm-generic/vmlinux.lds.h
++++ b/include/asm-generic/vmlinux.lds.h
+@@ -2,6 +2,18 @@
+ #define LOAD_OFFSET 0
+ #endif
++#ifndef SYMTAB_KEEP_STR
++#define SYMTAB_KEEP_STR *(__ksymtab_strings.*)
++#endif
++
++#ifndef SYMTAB_KEEP
++#define SYMTAB_KEEP *(__ksymtab.*)
++#endif
++
++#ifndef SYMTAB_KEEP_GPL
++#define SYMTAB_KEEP_GPL *(__ksymtab_gpl.*)
++#endif
++
+ #ifndef VMLINUX_SYMBOL
+ #define VMLINUX_SYMBOL(_sym_) _sym_
+ #endif
+@@ -124,35 +136,35 @@
+       /* Kernel symbol table: Normal symbols */                       \
+       __ksymtab         : AT(ADDR(__ksymtab) - LOAD_OFFSET) {         \
+               VMLINUX_SYMBOL(__start___ksymtab) = .;                  \
+-              *(__ksymtab)                                            \
++              SYMTAB_KEEP                                             \
+               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)                                        \
++              SYMTAB_KEEP_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)                                     \
++              *(__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)                                 \
++              *(__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)                                 \
++              *(__ksymtab_gpl_future.*)                               \
+               VMLINUX_SYMBOL(__stop___ksymtab_gpl_future) = .;        \
+       }                                                               \
+                                                                       \
+@@ -193,7 +205,13 @@
+                                                                       \
+       /* Kernel symbol table: strings */                              \
+         __ksymtab_strings : AT(ADDR(__ksymtab_strings) - LOAD_OFFSET) {       \
+-              *(__ksymtab_strings)                                    \
++              SYMTAB_KEEP_STR                                         \
++      }                                                               \
++                                                                      \
++      /DISCARD/ : {                                                   \
++              *(__ksymtab.*)                                          \
++              *(__ksymtab_gpl.*)                                      \
++              *(__ksymtab_strings.*)                                  \
+       }                                                               \
+                                                                       \
+       /* __*init sections */                                          \
+--- a/include/linux/module.h
++++ b/include/linux/module.h
+@@ -187,16 +187,24 @@ void *__symbol_get_gpl(const char *symbo
+ #define __CRC_SYMBOL(sym, sec)
+ #endif
++#ifdef MODULE
++#define __EXPORT_SUFFIX(sym)
++#else
++#define __EXPORT_SUFFIX(sym) "." #sym
++#endif
++
+ /* For every exported symbol, place a struct in the __ksymtab section */
+ #define __EXPORT_SYMBOL(sym, sec)                             \
+       extern typeof(sym) sym;                                 \
+       __CRC_SYMBOL(sym, sec)                                  \
+       static const char __kstrtab_##sym[]                     \
+-      __attribute__((section("__ksymtab_strings"), aligned(1))) \
++      __attribute__((section("__ksymtab_strings"              \
++        __EXPORT_SUFFIX(sym)), aligned(1)))                   \
+       = MODULE_SYMBOL_PREFIX #sym;                            \
+       static const struct kernel_symbol __ksymtab_##sym       \
+       __used                                                  \
+-      __attribute__((section("__ksymtab" sec), unused))       \
++      __attribute__((section("__ksymtab" sec                  \
++        __EXPORT_SUFFIX(sym)), unused))                       \
+       = { (unsigned long)&sym, __kstrtab_##sym }
+ #define EXPORT_SYMBOL(sym)                                    \
diff --git a/target/linux/generic-2.6/patches-2.6.30/028-module_exports.patch b/target/linux/generic-2.6/patches-2.6.30/028-module_exports.patch
new file mode 100644 (file)
index 0000000..ec037b3
--- /dev/null
@@ -0,0 +1,117 @@
+--- a/include/asm-generic/vmlinux.lds.h
++++ b/include/asm-generic/vmlinux.lds.h
+@@ -4,6 +4,18 @@
+ #define LOAD_OFFSET 0
+ #endif
++#ifndef SYMTAB_KEEP_STR
++#define SYMTAB_KEEP_STR *(__ksymtab_strings.*)
++#endif
++
++#ifndef SYMTAB_KEEP
++#define SYMTAB_KEEP *(__ksymtab.*)
++#endif
++
++#ifndef SYMTAB_KEEP_GPL
++#define SYMTAB_KEEP_GPL *(__ksymtab_gpl.*)
++#endif
++
+ #ifndef VMLINUX_SYMBOL
+ #define VMLINUX_SYMBOL(_sym_) _sym_
+ #endif
+@@ -176,35 +188,35 @@
+       /* Kernel symbol table: Normal symbols */                       \
+       __ksymtab         : AT(ADDR(__ksymtab) - LOAD_OFFSET) {         \
+               VMLINUX_SYMBOL(__start___ksymtab) = .;                  \
+-              *(__ksymtab)                                            \
++              SYMTAB_KEEP                                             \
+               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)                                        \
++              SYMTAB_KEEP_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)                                     \
++              *(__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)                                 \
++              *(__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)                                 \
++              *(__ksymtab_gpl_future.*)                               \
+               VMLINUX_SYMBOL(__stop___ksymtab_gpl_future) = .;        \
+       }                                                               \
+                                                                       \
+@@ -245,7 +257,13 @@
+                                                                       \
+       /* Kernel symbol table: strings */                              \
+         __ksymtab_strings : AT(ADDR(__ksymtab_strings) - LOAD_OFFSET) {       \
+-              *(__ksymtab_strings)                                    \
++              SYMTAB_KEEP_STR                                         \
++      }                                                               \
++                                                                      \
++      /DISCARD/ : {                                                   \
++              *(__ksymtab.*)                                          \
++              *(__ksymtab_gpl.*)                                      \
++              *(__ksymtab_strings.*)                                  \
+       }                                                               \
+                                                                       \
+       /* __*init sections */                                          \
+--- a/include/linux/module.h
++++ b/include/linux/module.h
+@@ -187,16 +187,24 @@ void *__symbol_get_gpl(const char *symbo
+ #define __CRC_SYMBOL(sym, sec)
+ #endif
++#ifdef MODULE
++#define __EXPORT_SUFFIX(sym)
++#else
++#define __EXPORT_SUFFIX(sym) "." #sym
++#endif
++
+ /* For every exported symbol, place a struct in the __ksymtab section */
+ #define __EXPORT_SYMBOL(sym, sec)                             \
+       extern typeof(sym) sym;                                 \
+       __CRC_SYMBOL(sym, sec)                                  \
+       static const char __kstrtab_##sym[]                     \
+-      __attribute__((section("__ksymtab_strings"), aligned(1))) \
++      __attribute__((section("__ksymtab_strings"              \
++        __EXPORT_SUFFIX(sym)), aligned(1)))                   \
+       = MODULE_SYMBOL_PREFIX #sym;                            \
+       static const struct kernel_symbol __ksymtab_##sym       \
+       __used                                                  \
+-      __attribute__((section("__ksymtab" sec), unused))       \
++      __attribute__((section("__ksymtab" sec                  \
++        __EXPORT_SUFFIX(sym)), unused))                       \
+       = { (unsigned long)&sym, __kstrtab_##sym }
+ #define EXPORT_SYMBOL(sym)                                    \
+--- a/Makefile
++++ b/Makefile
+@@ -994,7 +994,7 @@ prepare: prepare0
+ # Leave this as default for preprocessing vmlinux.lds.S, which is now
+ # done in arch/$(ARCH)/kernel/Makefile
+-export CPPFLAGS_vmlinux.lds += -P -C -U$(ARCH)
++export CPPFLAGS_vmlinux.lds += -P -C -U$(ARCH) $(EXTRA_LDSFLAGS)
+ # The asm symlink changes when $(ARCH) changes.
+ # Detect this and ask user to run make mrproper