1/* $NetBSD: x86_64.s,v 1.1 2022/10/14 19:41:18 ryo Exp $ */ 2 3/*- 4 * Copyright (c) 2022 The NetBSD Foundation, Inc. 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 NETBSD FOUNDATION, INC. AND CONTRIBUTORS 17 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 18 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 19 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 20 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 26 * POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29/* 30 * assemble & link: 31 * as -o x86_64.o x86_64.s 32 * ld -o hello -e _start x86_64.o 33 */ 34 35 /* ------------------------------------------------------------------ */ 36 37 /* 38 * This ELF section is used by the kernel to determine, among other 39 * things, the system call interface used by the binary. 40 * 41 * Normally, /usr/lib/crti.o is linked, but here it is written manually. 42 * 43 * SEE ALSO: 44 * - http://www.netbsd.org/docs/kernel/elf-notes.html 45 * - src/sys/sys/exec_elf.h 46 * - src/lib/csu/common/sysident.S 47 * - src/lib/csu/arch/x86_64/crti.S 48 */ 49 .section ".note.netbsd.ident", "a" 50 .p2align 2 51 .long 7 /* ELF_NOTE_NETBSD_NAMESZ */ 52 .long 4 /* ELF_NOTE_NETBSD_DESCSZ */ 53 .long 1 /* ELF_NOTE_TYPE_NETBSD_TAG */ 54 .ascii "NetBSD\0\0" /* ELF_NOTE_NETBSD_NAME */ 55 .long 999010000 /* __NetBSD_Version__ (sys/sys/param.h) */ 56 57 58 /* ------------------------------------------------------------------ */ 59 60 .section ".rodata" 61message: 62 .ascii "Hello, world!\n" 63 .set MESSAGE_SIZE, . - message 64 65 66 /* ------------------------------------------------------------------ */ 67 68 .section ".text" 69 .p2align 2 70 71 .global _start 72 .type _start, %function 73_start: 74 /* write(STDOUT_FILENO, message, MESSAGE_SIZE) */ 75 movl $1, %edi /* %edi: fd = STDOUT_FILENO */ 76 leaq message(%rip), %rsi /* %rsi: buf = message */ 77 movl $MESSAGE_SIZE, %edx /* %edx: nbytes = MESSAGE_SIZE */ 78 79 movl $4, %eax /* SYS_write */ 80 movq %rcx, %r10 81 syscall 82 83 /* exit(0) */ 84 xorl %edi, %edi /* %rdi: status = 0 */ 85 mov $1, %eax /* SYS_exit */ 86 movq %rcx, %r10 87 syscall 88 89 .size _start, . - _start 90