Implement the "abort" stub in assembly for ARM.

So that we can always get the full stack trace regardless of gcc's handling
of the "noreturn" attribute associated with abort().

[cherry-picked from master]

BUG:6455193
Change-Id: I0102355f5bf20e636d3feab9d1424495f38e39e2

libc/Android.mk

@@ -350,6 +350,7 @@ libc_common_src_files += \
 	arch-arm/bionic/__get_sp.S \
 	arch-arm/bionic/_exit_with_stack_teardown.S \
 	arch-arm/bionic/_setjmp.S \
+	arch-arm/bionic/abort_arm.S \
 	arch-arm/bionic/atomics_arm.c \
 	arch-arm/bionic/clone.S \
 	arch-arm/bionic/eabi.c \

libc/arch-arm/bionic/abort_arm.S

@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2012 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.
+ */
+
+#include <machine/asm.h>
+
+/*
+ * Coding the abort function in assembly so that registers are guaranteed to
+ * be preserved properly regardless of GCC's assumption on the "noreturn"
+ * attribute. When the registers are not properly preserved we won't be able
+ * to unwind the stack all the way to the bottom to fully reveal the call
+ * sequence when the crash happens.
+ */
+ENTRY(abort)
+    .save   {r3, r14}
+    stmfd   sp!, {r3, r14}
+    blx     PIC_SYM(_C_LABEL(__libc_android_abort), PLT)
+END(abort)

libc/unistd/abort.c

@@ -102,29 +102,3 @@ abort(void)
 	(void)kill(getpid(), SIGABRT);
 	_exit(1);
 }
-
-#ifdef __arm__
-/*
- * abort() does not return, which gcc interprets to mean that it doesn't
- * need to preserve any of the callee-save registers.  Unfortunately this
- * includes the link register, so if LR is used there is no way to determine
- * which function called abort().
- *
- * We work around this by inserting a trivial stub that doesn't alter
- * any of the "interesting" registers and thus doesn't need to save them.
- * We can't just call __libc_android_abort from C because gcc uses "bl"
- * without first saving LR, so we use an asm statement.  This also has
- * the side-effect of replacing abort() with __libc_android_abort() in
- * the stack trace.
- *
- * Ideally __libc_android_abort would be static, but I haven't figured out
- * how to tell gcc to call a static function from an asm statement.
- */
-void
-abort(void)
-{
-    asm ("b __libc_android_abort");
-    _exit(1);       /* suppress gcc noreturn warnings */
-}
-#endif
-