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