From 1da86d2f40f304d78b2ae4aac3b590b19adc7ce3 Mon Sep 17 00:00:00 2001
From: Denis Vlasenko <vda.linux@googlemail.com>
Date: Wed, 4 Jun 2008 11:28:24 +0000
Subject: build system: add PIE build option

---
 Makefile.flags | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

(limited to 'Makefile.flags')

diff --git a/Makefile.flags b/Makefile.flags
index 9525889c6..1cfda26ac 100644
--- a/Makefile.flags
+++ b/Makefile.flags
@@ -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
-- 
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