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build system: add PIE build option

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This commit is contained in:
Denis Vlasenko 2008-06-04 11:28:24 +00:00
parent 1e93f3c585
commit 1da86d2f40
5 changed files with 32 additions and 10 deletions
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8
Config.in
View File

@ -262,6 +262,14 @@ config STATIC
Most people will leave this set to 'N'.
config PIE
bool "Build BusyBox as a position independent executable"
default n
depends on !STATIC
help
(TODO: what is it and why/when is it useful?)
Most people will leave this set to 'N'.
config NOMMU
bool "Force NOMMU build"
default n

4
Makefile
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@ -315,6 +315,8 @@ AFLAGS_KERNEL =
# Use LINUXINCLUDE when you must reference the include/ directory.
# Needed to be compatible with the O= option
CFLAGS := $(CFLAGS)
# Added only to final link stage of busybox binary
CFLAGS_busybox := $(CFLAGS_busybox)
CPPFLAGS := $(CPPFLAGS)
AFLAGS := $(AFLAGS)
LDFLAGS := $(LDFLAGS)
@ -580,7 +582,7 @@ quiet_cmd_busybox__ ?= LINK $@
cmd_busybox__ ?= $(srctree)/scripts/trylink \
"$@" \
"$(CC)" \
"$(CFLAGS)" \
"$(CFLAGS) $(CFLAGS_busybox)" \
"$(LDFLAGS) $(EXTRA_LDFLAGS)" \
"$(core-y)" \
"$(libs-y)" \

20
Makefile.flags
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@ -50,17 +50,31 @@ ifeq ($(CONFIG_DEBUG),y)
CFLAGS += $(call cc-option,-g)
endif
# If arch/$(ARCH)/Makefile did not override it (with, say, -fPIC)...
ARCH_FPIC ?= -fpic
ARCH_FPIE ?= -fpie
ARCH_PIE ?= -pie
ifeq ($(CONFIG_BUILD_LIBBUSYBOX),y)
# on i386: 14% smaller libbusybox.so
# (code itself is 9% bigger, we save on relocs/PLT/GOT)
CFLAGS += -fpic
CFLAGS += $(ARCH_FPIC)
# and another 4% reduction of libbusybox.so:
# (external entry points must be marked EXTERNALLY_VISIBLE)
CFLAGS += $(call cc-option,-fvisibility=hidden)
endif
ifeq ($(CONFIG_STATIC),y)
LDFLAGS += -static
CFLAGS_busybox += -static
endif
ifeq ($(CONFIG_PIE),y)
CFLAGS_busybox += $(ARCH_PIE)
CFLAGS += $(ARCH_FPIE)
# No switch() jump tables. Code growth +1k, binary size down -12k
# due to reduced number of code pointers.
# (TODO: make overridable: some arches may want to not do this)
CFLAGS += $(call cc-option,-fno-jump-tables)
endif
LDLIBS += m crypt
@ -81,8 +95,6 @@ ifeq ($(CONFIG_DMALLOC),y)
LDLIBS += dmalloc
endif
#LDFLAGS += -nostdlib
LDFLAGS_ELF2FLT = -Wl,-elf2flt
ifneq (,$(findstring $(LDFLAGS_ELF2FLT),$(LDFLAGS)))
SKIP_STRIP = y

6
scripts/Makefile.IMA
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@ -45,8 +45,8 @@ STRIP = $(CROSS_COMPILE)strip
OBJCOPY = $(CROSS_COMPILE)objcopy
OBJDUMP = $(CROSS_COMPILE)objdump
CFLAGS := $(CFLAGS)
CPPFLAGS+= -D"KBUILD_STR(s)=\#s" #-Q
CFLAGS := $(CFLAGS)
CPPFLAGS += -D"KBUILD_STR(s)=\#s" #-Q
# We need some generic definitions
include $(srctree)/scripts/Kbuild.include
@ -180,7 +180,7 @@ busybox_unstripped.o: $(usage_stuff) include/applet_tables.h include/autoconf.h
busybox: busybox_unstripped.o
$(srctree)/scripts/trylink \
busybox_unstripped \
"$(CC)" \
"$(CC) $(CFLAGS_busybox)" \
"$(CFLAGS)" \
"$(LDFLAGS)" \
"busybox_unstripped.o" \

4
scripts/Makefile.build
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@ -251,8 +251,8 @@ ifdef builtin-target
quiet_cmd_link_o_target = LD $@
# If the list of objects to link is empty, just create an empty built-in.o
cmd_link_o_target = $(if $(strip $(obj-y)),\
$(LD) $(ld_flags) -r -o $@ $(filter $(obj-y), $^),\
rm -f $@; $(AR) rcs $@)
$(LD) $(ld_flags) -r -o $@ $(filter $(obj-y), $^),\
rm -f $@; $(AR) rcs $@)
$(builtin-target): $(obj-y) FORCE
$(call if_changed,link_o_target)