Switch x86 begin.c to asm; align ESP correctly
Every other architecture already uses an assembly file here.
The previous code aligned ESP incorrectly, but it doesn't really matter
because everything is built with Clang's -mstackrealign, which realigns
ESP in every function prologue.
Bug: http://b/73140672#comment4
Test: lunch aosp_x86-eng; m; emulator; device boots
Test: manual
Change-Id: I921fd7848cdc611b4f8f13d1176d1983ffea952d
diff --git a/linker/arch/x86/begin.S b/linker/arch/x86/begin.S
new file mode 100644
index 0000000..3812646
--- /dev/null
+++ b/linker/arch/x86/begin.S
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2018 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 <private/bionic_asm.h>
+
+ENTRY(_start)
+ // Force unwinds to end in this function.
+ .cfi_undefined %eip
+
+ movl %esp, %eax // %esp is aligned to 16 here.
+ subl $12, %esp
+ pushl %eax
+ call __linker_init // %esp is aligned to 16 before the call.
+ addl $16, %esp
+
+ /* linker init returns (%eax) the _entry address in the main image */
+ jmp *%eax
+END(_start)