Revert "Replaces vfork() implementation with fork()"

We're getting cold feet on this one... let's put it back.

This reverts commit 210331d9762037afb9b5ed8413079c6f65872df9.

Change-Id: I6b0d3c2b1dbf7f1dc9566979a91b7504c2189269
diff --git a/libc/arch-mips64/bionic/vfork.S b/libc/arch-mips64/bionic/vfork.S
new file mode 100644
index 0000000..911a264
--- /dev/null
+++ b/libc/arch-mips64/bionic/vfork.S
@@ -0,0 +1,71 @@
+/*
+ * 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.
+ */
+
+#include <private/bionic_asm.h>
+#include <linux/sched.h>
+
+// TODO: mips' uapi signal.h is missing #ifndef __ASSEMBLY__.
+// #include <asm/signal.h>
+#define SIGCHLD 18
+
+	.text
+
+#if (_MIPS_SIM == _ABIO32) || (_MIPS_SIM == _ABI32)
+FRAMESZ		=	MKFSIZ(5,0)
+#else
+FRAMESZ		=	MKFSIZ(0,0)
+#endif
+
+LEAF(vfork,FRAMESZ)
+#if FRAMESZ!=0
+	PTR_SUBU sp, FRAMESZ
+#endif
+	SETUP_GP64(a5, vfork)
+	LI	a0, (CLONE_VM | CLONE_VFORK | SIGCHLD)
+	move	a1, $0
+	move	a2, $0
+	move	a3, $0
+#if (_MIPS_SIM == _ABIO32) || (_MIPS_SIM == _ABI32)
+	REG_S	$0, 4*REGSZ(sp)
+#else
+	move	a4, $0
+#endif
+	LI	v0, __NR_clone
+	syscall
+#if FRAMESZ!=0
+	PTR_ADDU sp,FRAMESZ
+#endif
+	move	a0, v0
+	bnez	a3, 1f
+	RESTORE_GP64
+	j	ra
+1:
+	LA	t9,__set_errno
+	RESTORE_GP64
+	j	t9
+	END(vfork)
diff --git a/libc/arch-mips64/mips64.mk b/libc/arch-mips64/mips64.mk
index 6f7a928..230cb26 100644
--- a/libc/arch-mips64/mips64.mk
+++ b/libc/arch-mips64/mips64.mk
@@ -46,6 +46,7 @@
     arch-mips64/bionic/setjmp.S \
     arch-mips64/bionic/sigsetjmp.S \
     arch-mips64/bionic/syscall.S \
+    arch-mips64/bionic/vfork.S \
 
 # FIXME TODO
 ## libc_bionic_src_files_mips64 += arch-mips64/string/memcpy.S