-#include <machine/asm.h>
-#include <asm/unistd.h>
-
-/* Get rid of the stack modifications (popl/ret) after vfork() success.
- * vfork is VERY sneaky. One has to be very careful about what can be done
- * between a successful vfork and a a subsequent execve()
+/*
+ * 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>
+
+// This custom code preserves the return address across the system call.
+
ENTRY(vfork)
- /* grab the return address */
- popl %ecx
- movl $__NR_vfork, %eax
- int $0x80
- cmpl $-129, %eax
- jb 1f
- negl %eax
- pushl %eax
- call __set_errno
- orl $-1, %eax
+ popl %ecx // Grab the return address.
+ movl $__NR_vfork, %eax
+ int $0x80
+ cmpl $-MAX_ERRNO, %eax
+ jb 1f
+ negl %eax
+ pushl %eax
+ call __set_errno
+ orl $-1, %eax
1:
- jmp *%ecx
+ jmp *%ecx // Jump to the stored return address.
END(vfork)