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-rw-r--r--sysdeps/unix/bsd/i386/vfork.S39
1 files changed, 39 insertions, 0 deletions
diff --git a/sysdeps/unix/bsd/i386/vfork.S b/sysdeps/unix/bsd/i386/vfork.S
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+/* Copyright (C) 1993, 1994, 1995 Free Software Foundation, Inc.
+This file is part of the GNU C Library.
+
+The GNU C Library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Library General Public License as
+published by the Free Software Foundation; either version 2 of the
+License, or (at your option) any later version.
+
+The GNU C Library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with the GNU C Library; see the file COPYING.LIB.  If
+not, write to the Free Software Foundation, Inc., 675 Mass Ave,
+Cambridge, MA 02139, USA.  */
+
+#include <sysdep.h>
+
+/* Since vfork shares the address space between the parent and child,
+   we must take care to avoid the child unwinding the stack frame and
+   clobbering it for the parent.  */
+
+.text
+ENTRY (__vfork)
+	popl scratch		/* Save the return PC in a register.  */
+	DO_CALL (vfork, 0)	/* Do the system call.  */
+	pushl scratch		/* Put the return PC back on the stack.  */
+	jb syscall_error	/* Branch if error.  */
+	/* R1 is now 0 for the parent and 1 for the child.  Decrement it to
+	   make it -1 (all bits set) for the parent, and 0 (no bits set)
+	   for the child.  Then AND it with R0, so the parent gets
+	   R0&-1==R0, and the child gets R0&0==0.  */
+	decl r1
+	andl r1, r0
+	ret
+
+weak_alias (__vfork, vfork)