Enable functional DSO object destruction

Unfortunately, legacy .so files for ARM don't have a correct crtbegin file.
Consequently, we have to grandfather the old __dso_handle behaviour.
Add some ifdefs for ARM to allow it to use the old code until we can work
out a transition.

Change-Id: I6a28f368267d792c94e1d985d8344023bc632f6f
Author: H.J. Lu <hongjiu.lu@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
diff --git a/libc/arch-x86/bionic/atexit.S b/libc/arch-x86/bionic/atexit.S
new file mode 100644
index 0000000..b28f40b
--- /dev/null
+++ b/libc/arch-x86/bionic/atexit.S
@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+	.text
+	.p2align 4,,15
+	.globl	atexit
+	.hidden	atexit
+	.type	atexit, @function
+atexit:
+	pushl	%ebp
+	movl	%esp, %ebp
+	pushl	%ebx
+	call	__x86.get_pc_thunk.bx
+	addl	$_GLOBAL_OFFSET_TABLE_, %ebx
+	subl	$20, %esp
+	movl	$0, 4(%esp)
+	movl	__dso_handle@GOTOFF(%ebx), %eax
+	movl	%eax, 8(%esp)
+	movl	8(%ebp), %eax
+	movl	%eax, (%esp)
+	call	__cxa_atexit@PLT
+	addl	$20, %esp
+	popl	%ebx
+	popl	%ebp
+	ret
+	.size	atexit, .-atexit
+
+	.section	.text.__x86.get_pc_thunk.bx,"axG",@progbits,__x86.get_pc_thunk.bx,comdat
+	.globl	__x86.get_pc_thunk.bx
+	.hidden	__x86.get_pc_thunk.bx
+	.type	__x86.get_pc_thunk.bx, @function
+__x86.get_pc_thunk.bx:
+	nop
+	nop
+	nop
+	nop
+	nop
+	nop
+	nop
+	nop
+	movl	(%esp), %ebx
+	ret