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

2 files changed, 9 insertions, 23 deletions

diff --git a/libc/private/__dso_handle.S b/libc/private/__dso_handle.h
index 3e80128..e67ce7c 100644
--- a/libc/private/__dso_handle.S
+++ b/libc/private/__dso_handle.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2010 The Android Open Source Project
+ * Copyright (C) 2012 The Android Open Source Project
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -26,17 +26,9 @@
  * SUCH DAMAGE.
  */
 
-# The __dso_handle global variable is used by static
-# C++ constructors and destructors in the binary.
-# See http://www.codesourcery.com/public/cxx-abi/abi.html#dso-dtor
-#
-        .section .bss
-        .align 4
 
 #ifndef CRT_LEGACY_WORKAROUND
-	.hidden __dso_handle
+__attribute__ ((visibility ("hidden")))
 #endif
-
-        .globl __dso_handle
-__dso_handle:
-        .long 0
+__attribute__ ((section (".bss")))
+void *__dso_handle = (void *) 0;
diff --git a/libc/private/__dso_handle_so.S b/libc/private/__dso_handle_so.c
index 77a5d7f..198e64b 100644
--- a/libc/private/__dso_handle_so.S
+++ b/libc/private/__dso_handle_so.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2010 The Android Open Source Project
+ * Copyright (C) 2012 The Android Open Source Project
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -26,13 +26,7 @@
  * SUCH DAMAGE.
  */
 
-# The __dso_handle global variable is used by static
-# C++ constructors and destructors in the binary.
-# See http://www.codesourcery.com/public/cxx-abi/abi.html#dso-dtor
-#
-	.data
-        .align 4
-	.hidden __dso_handle
-        .globl __dso_handle
-__dso_handle:
-        .long __dso_handle
+
+__attribute__ ((visibility ("hidden")))
+__attribute__ ((section (".data")))
+void *__dso_handle;