1/*-
2 * Copyright (c) 1990 The Regents of the University of California.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by the University of
16 *	California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 *
33 * $FreeBSD: src/sys/i386/i386/exception.s,v 1.65.2.3 2001/08/15 01:23:49 peter Exp $
34 */
35
36#include <machine/asmacros.h>
37#include <machine/segments.h>
38#include <machine/lock.h>
39#include <machine/psl.h>
40#include <machine/trap.h>
41
42#include "assym.s"
43
44	.text
45
46	.globl	lwkt_switch_return
47
48/*
49 * This function is what cpu_heavy_restore jumps to after a new process
50 * is created.  The LWKT subsystem switches while holding a critical
51 * section and we maintain that abstraction here (e.g. because
52 * cpu_heavy_restore needs it due to PCB_*() manipulation), then get out of
53 * it before calling the initial function (typically fork_return()) and/or
54 * returning to user mode.
55 *
56 * The MP lock is not held at any point but the critcount is bumped
57 * on entry to prevent interruption of the trampoline at a bad point.
58 *
59 * This is effectively what td->td_switch() returns to.  It 'returns' the
60 * old thread in %eax and since this is not returning to a td->td_switch()
61 * call from lwkt_switch() we must handle the cleanup for the old thread
62 * by calling lwkt_switch_return().
63 *
64 * fork_trampoline(%rax:otd, %rbp:func, %r12:arg)
65 */
66ENTRY(fork_trampoline)
67	movq	%rax,%rdi
68	call	lwkt_switch_return
69	movq	PCPU(curthread),%rax
70	decl	TD_CRITCOUNT(%rax)
71
72	/*
73	 * cpu_set_fork_handler intercepts this function call to
74	 * have this call a non-return function to stay in kernel mode.
75	 *
76	 * initproc has its own fork handler, start_init(), which DOES
77	 * return.
78	 *
79	 * %rbx - chaining function (typically fork_return)
80	 * %r12 -> %rdi (argument)
81	 * frame-> %rsi (trap frame)
82	 *
83	 *   void (func:rbx)(arg:rdi, trapframe:rsi)
84	 */
85	movq	%rsp, %rsi		/* pass trapframe by reference */
86	movq	%r12, %rdi		/* arg1 */
87	call	*%rbx			/* function */
88
89	/* cut from syscall */
90
91	call	splz
92
93	/*
94	 * Return via doreti to handle ASTs.
95	 *
96	 * trapframe is at the top of the stack.
97	 */
98	MEXITCOUNT
99	pushq	$0		/* if_vec */
100	movq	%rsp,%rdi	/* pass by reference */
101	call	go_user
102	/* NOT REACHED */
103