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/* $OpenBSD: tfork_thread.S,v 1.10 2020/10/18 14:28:17 deraadt Exp $ */
/*-
* Copyright (c) 2000 Peter Wemm <peter@FreeBSD.org>
* Copyright (c) 2003 Alan L. Cox <alc@cs.rice.edu>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <machine/asm.h>
/*
* With thanks to John Dyson for the original version of this.
*/
#include "SYS.h"
/*
* %rdi %rsi %rdx %rcx
* __tfork_thread(param, psize, start_fnc, start_arg);
*
* param: Argument to pass to the actual kernel call.
* psize: Other argument to pass to the actual kernel call.
* start_fnc: Address of thread function to call in child.
* start_arg: Argument to pass to the thread function in child.
*/
ENTRY(__tfork_thread)
.cfi_startproc
movq %rdx, %r8
movq %rcx, %r9
/*
* Prepare and execute the thread creation syscall
*/
movl $SYS___tfork, %eax
.cfi_endproc
syscall
jb 2f
/*
* Check to see if we are in the parent or child
*/
cmpl $0, %eax
jz 1f
ret
/* the retpoline we'll use to call the child's main */
_ALIGN_TRAPS
.cfi_startproc
0: JMP_RETPOLINE(r8)
/*
* If we are in the child (new thread), then
* set-up the call to the internal subroutine. If it
* returns, then call __threxit.
*/
_ALIGN_TRAPS
1:
/* Mark top frame of new thread in CFI and with zero FP */
.cfi_undefined rip
.cfi_undefined rsp
xorl %ebp, %ebp
movq %r9, %rdi
call 0b
/*
* Thread exit system call
*/
movl $SYS___threxit, %eax
xorl %edi, %edi
syscall
int3
/*
* Branch here if the thread creation fails:
*/
2:
SET_ERRNO
ret
.cfi_endproc
END(__tfork_thread)
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