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 * $DragonFly: src/sys/platform/vkernel/i386/fork_tramp.s,v 1.3 2007/01/22 19:37:04 corecode Exp $
35 */
36
37#include <machine/asmacros.h>
38#include <machine/segments.h>
39#include <machine/lock.h>
40#include <machine/psl.h>
41#include <machine/trap.h>
42
43#include "assym.s"
44
45	.text
46
47/*
48 * This function is what cpu_heavy_restore jumps to after a new process
49 * is created.  The LWKT subsystem switches while holding a critical
50 * section and we maintain that abstraction here (e.g. because
51 * cpu_heavy_restore needs it due to PCB_*() manipulation), then get out of
52 * it before calling the initial function (typically fork_return()) and/or
53 * returning to user mode.
54 *
55 * The MP lock is held on entry, but for processes fork_return(esi)
56 * releases it.  'doreti' always runs without the MP lock.
57 */
58ENTRY(fork_trampoline)
59	movq	PCPU(curthread),%rax
60	subl	$TDPRI_CRIT,TD_PRI(%rax)
61
62	/*
63	 * cpu_set_fork_handler intercepts this function call to
64	 * have this call a non-return function to stay in kernel mode.
65	 *
66	 * initproc has its own fork handler, start_init(), which DOES
67	 * return.
68	 *
69	 * %rbx - chaining function (typically fork_return)
70	 * %r12 -> %rdi (argument)
71	 * frame-> %rsi (trap frame)
72	 *
73	 *   void (func:rbx)(arg:rdi, trapframe:rsi)
74	 */
75	movq	%rsp, %rsi		/* pass trapframe by reference */
76	movq	%r12, %rdi		/* arg1 */
77	call	*%rbx			/* function */
78
79	/* cut from syscall */
80
81	call	splz
82
83#if defined(INVARIANTS) && defined(SMP)
84	movq	PCPU(curthread),%rax
85	cmpl	$0,TD_MPCOUNT(%rax)
86	je	1f
87	movq	$pmsg4, %rdi
88	movl	TD_MPCOUNT(%rax), %esi
89	movq	%rbx, %rdx
90	xorl	%eax, %eax
91	call	panic
92pmsg4:  .asciz	"fork_trampoline mpcount %d after calling %p"
93	/* JG what's the purpose of this alignment and is it enough on amd64? */
94	.p2align 2
951:
96#endif
97	/*
98	 * Return via doreti to handle ASTs.
99	 *
100	 * trapframe is at the top of the stack.
101	 */
102	MEXITCOUNT
103	pushq	$0		/* if_vec */
104	movq	%rsp,%rdi	/* pass by reference */
105	call	go_user
106	/* NOT REACHED */
107