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