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add an optional config option for stripping all unnecessary symbol exports from the kernel image

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SVN-Revision: 17181
This commit is contained in:
Felix Fietkau 2009-08-08 14:22:04 +00:00
parent 253c9fcf7d
commit bb5a40c64b
5 changed files with 270 additions and 1 deletions
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8
Config.in
View file

@ -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

24
include/kernel-build.mk
View 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 $$@

5
include/kernel-defaults.mk
View 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))

117
target/linux/generic-2.6/patches-2.6.28/027-module_exports.patch Normal file
View file

@ -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) \

117
target/linux/generic-2.6/patches-2.6.30/028-module_exports.patch Normal file
View file

@ -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