commit 9d40326830c2bd407427889c554adeb915ee6b4a
author Nick Kralevich <nnk@google.com> Thu May 31 11:40:10 2012 -0700
committer Nick Kralevich <nnk@google.com> Fri Jun 01 14:41:27 2012 -0700
tree 17c901c0eb9768711be1c299178cbd891624281b
parent 857fc9eab912fbb3f27913c3582ed2268420bce9

arm: rewrite crtbegin* as C files.

Rewrite
 crtbegin.S     -> crtbegin.c
 crtbegin_so.S  -> crtbegin_so.c

This change allows us to generate PIC code without relying
on text relocations.

As a consequence of this rewrite, also rewrite
  __dso_handle.S    -> __dso_handle.c
  __dso_handle_so.S -> __dso_handle_so.c
  atexit.S          -> atexit.c

In crtbegin.c _start, place the __PREINIT_ARRAY__, __INIT_ARRAY__,
__FINI_ARRAY__, and __CTOR_LIST__ variables onto the stack, instead of
passing a pointer to the text section of the binary.

This change appears sorta wonky, as I attempted to preserve,
as much as possible, the structure of the original assembly.
As a result, you have C files including other C files, and other
programming uglyness.

Result: This change reduces the number of files with text-relocations
from 315 to 19 on my Android build.

Before:
  $ scanelf -aR $OUT/system | grep TEXTREL | wc -l
  315

After:
  $ scanelf -aR $OUT/system | grep TEXTREL | wc -l
  19

Change-Id: Ib9f98107c0eeabcb606e1ddc7ed7fc4eba01c9c4

libc/Android.mk

diff --git a/libc/Android.mk b/libc/Android.mk
index 77da9c8..9887589 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -515,8 +515,8 @@
     libc_common_cflags += -DANDROID_SMP=0
 endif
 
-# Needed to access private/__dso_handle.S from
-# crtbegin_xxx.S and crtend_xxx.S
+# Needed to access private/__dso_handle.h from
+# crtbegin_xxx.c and crtend_xxx.c
 #
 libc_crt_target_cflags += -I$(LOCAL_PATH)/private
 
@@ -531,9 +531,8 @@
 		$(LOCAL_PATH)/string  \
 		$(LOCAL_PATH)/stdio
 
-# Needed to access private/__dso_handle.S from
+# Needed to access private/__dso_handle.h from
 # crtbegin_xxx.S and crtend_xxx.S
-# and machine/asm.h
 #
 libc_crt_target_cflags += -I$(LOCAL_PATH)/private -I$(LOCAL_PATH)/arch-$(TARGET_ARCH)/include
 
@@ -555,12 +554,16 @@
 #
 
 libc_crt_target_so_cflags := $(libc_crt_target_cflags)
+libc_crt_target_crtstart_file := $(LOCAL_PATH)/arch-$(TARGET_ARCH)/bionic/crtbegin.c
+libc_crt_target_crtstart_so_file := $(LOCAL_PATH)/arch-$(TARGET_ARCH)/bionic/crtbegin_so.c
 ifeq ($(TARGET_ARCH),x86)
     # This flag must be added for x86 targets, but not for ARM
     libc_crt_target_so_cflags += -fPIC
+    libc_crt_target_crtstart_file := $(LOCAL_PATH)/arch-$(TARGET_ARCH)/bionic/crtbegin.S
+    libc_crt_target_crtstart_so_file := $(LOCAL_PATH)/arch-$(TARGET_ARCH)/bionic/crtbegin_so.S
 endif
 GEN := $(TARGET_OUT_INTERMEDIATE_LIBRARIES)/crtbegin_so.o
-$(GEN): $(LOCAL_PATH)/arch-$(TARGET_ARCH)/bionic/crtbegin_so.S
+$(GEN): $(libc_crt_target_crtstart_so_file)
 	@mkdir -p $(dir $@)
 	$(TARGET_CC) $(libc_crt_target_so_cflags) -o $@ -c $<
 ALL_GENERATED_SOURCES += $(GEN)
@@ -574,13 +577,13 @@
 
 
 GEN := $(TARGET_OUT_INTERMEDIATE_LIBRARIES)/crtbegin_static.o
-$(GEN): $(LOCAL_PATH)/arch-$(TARGET_ARCH)/bionic/crtbegin.S
+$(GEN): $(libc_crt_target_crtstart_file)
 	@mkdir -p $(dir $@)
 	$(TARGET_CC) $(libc_crt_target_cflags) -o $@ -c $<
 ALL_GENERATED_SOURCES += $(GEN)
 
 GEN := $(TARGET_OUT_INTERMEDIATE_LIBRARIES)/crtbegin_dynamic.o
-$(GEN): $(LOCAL_PATH)/arch-$(TARGET_ARCH)/bionic/crtbegin.S
+$(GEN): $(libc_crt_target_crtstart_file)
 	@mkdir -p $(dir $@)
 	$(TARGET_CC) $(libc_crt_target_cflags) -o $@ -c $<
 ALL_GENERATED_SOURCES += $(GEN)