1/* $OpenBSD: tfork_thread.S,v 1.10 2020/10/18 14:28:17 deraadt Exp $ */ 2/*- 3 * Copyright (c) 2000 Peter Wemm <peter@FreeBSD.org> 4 * Copyright (c) 2003 Alan L. Cox <alc@cs.rice.edu> 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29#include <machine/asm.h> 30 31/* 32 * With thanks to John Dyson for the original version of this. 33 */ 34 35#include "SYS.h" 36 37/* 38 * %rdi %rsi %rdx %rcx 39 * __tfork_thread(param, psize, start_fnc, start_arg); 40 * 41 * param: Argument to pass to the actual kernel call. 42 * psize: Other argument to pass to the actual kernel call. 43 * start_fnc: Address of thread function to call in child. 44 * start_arg: Argument to pass to the thread function in child. 45 */ 46 47ENTRY(__tfork_thread) 48 .cfi_startproc 49 movq %rdx, %r8 50 movq %rcx, %r9 51 52 /* 53 * Prepare and execute the thread creation syscall 54 */ 55 movl $SYS___tfork, %eax 56 .cfi_endproc 57 syscall 58 jb 2f 59 60 /* 61 * Check to see if we are in the parent or child 62 */ 63 cmpl $0, %eax 64 jz 1f 65 ret 66 67 /* the retpoline we'll use to call the child's main */ 68 _ALIGN_TRAPS 69 .cfi_startproc 700: JMP_RETPOLINE(r8) 71 72 /* 73 * If we are in the child (new thread), then 74 * set-up the call to the internal subroutine. If it 75 * returns, then call __threxit. 76 */ 77 _ALIGN_TRAPS 781: 79 /* Mark top frame of new thread in CFI and with zero FP */ 80 .cfi_undefined rip 81 .cfi_undefined rsp 82 xorl %ebp, %ebp 83 movq %r9, %rdi 84 call 0b 85 86 /* 87 * Thread exit system call 88 */ 89 movl $SYS___threxit, %eax 90 xorl %edi, %edi 91 syscall 92 int3 93 94 /* 95 * Branch here if the thread creation fails: 96 */ 972: 98 SET_ERRNO 99 ret 100 .cfi_endproc 101END(__tfork_thread) 102