/* $NetBSD: x86_64.s,v 1.1 2022/10/14 19:41:18 ryo Exp $ */
/*-
* Copyright (c) 2022 The NetBSD Foundation, Inc.
* 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
*/
/*
* assemble & link:
* as -o x86_64.o x86_64.s
* ld -o hello -e _start x86_64.o
*/
/* ------------------------------------------------------------------ */
/*
* This ELF section is used by the kernel to determine, among other
* things, the system call interface used by the binary.
*
* Normally, /usr/lib/crti.o is linked, but here it is written manually.
*
* SEE ALSO:
* -
http://www.netbsd.org/docs/kernel/elf-notes.html
* - src/sys/sys/exec_elf.h
* - src/lib/csu/common/sysident.S
* - src/lib/csu/arch/x86_64/crti.S
*/
.section ".note.netbsd.ident", "a"
.p2align 2
.long 7 /* ELF_NOTE_NETBSD_NAMESZ */
.long 4 /* ELF_NOTE_NETBSD_DESCSZ */
.long 1 /* ELF_NOTE_TYPE_NETBSD_TAG */
.ascii "NetBSD\0\0" /* ELF_NOTE_NETBSD_NAME */
.long 999010000 /* __NetBSD_Version__ (sys/sys/param.h) */
/* ------------------------------------------------------------------ */
.section ".rodata"
message:
.ascii "Hello, world!\n"
.set MESSAGE_SIZE, . - message
/* ------------------------------------------------------------------ */
.section ".text"
.p2align 2
.global _start
.type _start, %function
_start:
/* write(STDOUT_FILENO, message, MESSAGE_SIZE) */
movl $1, %edi /* %edi: fd = STDOUT_FILENO */
leaq message(%rip), %rsi /* %rsi: buf = message */
movl $MESSAGE_SIZE, %edx /* %edx: nbytes = MESSAGE_SIZE */
movl $4, %eax /* SYS_write */
movq %rcx, %r10
syscall
/* exit(0) */
xorl %edi, %edi /* %rdi: status = 0 */
mov $1, %eax /* SYS_exit */
movq %rcx, %r10
syscall
.size _start, . - _start
