From 9ea4d5f3a852a03b5a2c5676da148a2779821518 Mon Sep 17 00:00:00 2001
From: Elliott Hughes <enh@google.com>
Date: Fri, 18 Oct 2013 18:21:11 -0700
Subject: [PATCH] Fix the x86_64 vfork implementation.

Change-Id: I599507f5058e6196dc2d5b5653d06d5135dd8ac1
---
 libc/SYSCALLS.TXT                 |  2 +-
 libc/arch-x86_64/bionic/vfork.S   | 48 +++++++++++++++++++++++++++++++
 libc/arch-x86_64/syscalls.mk      |  1 -
 libc/arch-x86_64/syscalls/vfork.S | 18 ------------
 libc/arch-x86_64/x86_64.mk        |  1 +
 5 files changed, 50 insertions(+), 20 deletions(-)
 create mode 100644 libc/arch-x86_64/bionic/vfork.S
 delete mode 100644 libc/arch-x86_64/syscalls/vfork.S

diff --git a/libc/SYSCALLS.TXT b/libc/SYSCALLS.TXT
index cb9af1c19..d9a250672 100644
--- a/libc/SYSCALLS.TXT
+++ b/libc/SYSCALLS.TXT
@@ -83,7 +83,7 @@ int     getrusage(int who, struct rusage*  r_usage)  all
 int     setgroups:setgroups32(int, const gid_t*)   arm,x86
 int     setgroups:setgroups(int, const gid_t*)     mips,x86_64
 int     setpgid(pid_t, pid_t)  all
-pid_t   vfork(void)  arm,x86_64
+pid_t   vfork(void)  arm
 int     setregid:setregid32(gid_t, gid_t)  arm,x86
 int     setregid:setregid(gid_t, gid_t)    mips,x86_64
 int     chroot(const char*)  all
diff --git a/libc/arch-x86_64/bionic/vfork.S b/libc/arch-x86_64/bionic/vfork.S
new file mode 100644
index 000000000..ad73cf68a
--- /dev/null
+++ b/libc/arch-x86_64/bionic/vfork.S
@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2013 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 <asm/unistd.h>
+#include <linux/err.h>
+#include <machine/asm.h>
+
+// This custom code preserves the return address across the system call.
+
+ENTRY(vfork)
+  popq    %rdi  // Grab the return address.
+  movl    $__NR_vfork, %eax
+  syscall
+  pushq   %rdi  // Restore the return address.
+  cmpq    $-MAX_ERRNO, %rax
+  jb      1f
+  negl    %eax
+  movl    %eax, %edi
+  call    __set_errno
+  orq     $-1, %rax
+1:
+  ret
+END(vfork)
diff --git a/libc/arch-x86_64/syscalls.mk b/libc/arch-x86_64/syscalls.mk
index beb4afa14..70cc3191c 100644
--- a/libc/arch-x86_64/syscalls.mk
+++ b/libc/arch-x86_64/syscalls.mk
@@ -198,7 +198,6 @@ syscall_src += arch-x86_64/syscalls/unlinkat.S
 syscall_src += arch-x86_64/syscalls/unshare.S
 syscall_src += arch-x86_64/syscalls/utimensat.S
 syscall_src += arch-x86_64/syscalls/utimes.S
-syscall_src += arch-x86_64/syscalls/vfork.S
 syscall_src += arch-x86_64/syscalls/wait4.S
 syscall_src += arch-x86_64/syscalls/write.S
 syscall_src += arch-x86_64/syscalls/writev.S
diff --git a/libc/arch-x86_64/syscalls/vfork.S b/libc/arch-x86_64/syscalls/vfork.S
deleted file mode 100644
index 18ee2f836..000000000
--- a/libc/arch-x86_64/syscalls/vfork.S
+++ /dev/null
@@ -1,18 +0,0 @@
-/* Generated by gensyscalls.py. Do not edit. */
-
-#include <asm/unistd.h>
-#include <linux/err.h>
-#include <machine/asm.h>
-
-ENTRY(vfork)
-    movl    $__NR_vfork, %eax
-    syscall
-    cmpq    $-MAX_ERRNO, %rax
-    jb      1f
-    negl    %eax
-    movl    %eax, %edi
-    call    __set_errno
-    orq     $-1, %rax
-1:
-    ret
-END(vfork)
diff --git a/libc/arch-x86_64/x86_64.mk b/libc/arch-x86_64/x86_64.mk
index b17b1384e..212eebe51 100644
--- a/libc/arch-x86_64/x86_64.mk
+++ b/libc/arch-x86_64/x86_64.mk
@@ -9,6 +9,7 @@ _LIBC_ARCH_COMMON_SRC_FILES := \
     arch-x86_64/bionic/__set_tls.c \
     arch-x86_64/bionic/sigsetjmp.S \
     arch-x86_64/bionic/syscall.S \
+    arch-x86_64/bionic/vfork.S \
     arch-x86_64/string/ffs.S \
     string/memcmp16.c \