59 lines
1.7 KiB
ArmAsm
59 lines
1.7 KiB
ArmAsm
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/*
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* GNU Mes --- Maxwell Equations of Software
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* Copyright © 2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
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*
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* This file is part of GNU Mes.
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*
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* GNU Mes is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or (at
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* your option) any later version.
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*
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* GNU Mes is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GNU Mes. If not, see <http://www.gnu.org/licenses/>.
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*/
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/** Commentary: */
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/* Using gdb, esp. GUD in GNU Emacs is recommended
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M-x gdb-display-disassembly-buffer
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M-x gdb-display-io-buffer
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set disassemble-next-line on
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break _start
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run
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info registers
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si
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p/x $rax
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RET
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...
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*/
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/** Code: */
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SYS_exit = 0x3c /* Linux syscalls. */
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SYS_write = 0x01
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stdout = 1 /* File discriptor */
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.globl _start /* Magic linker symbol: --entry-address. */
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.text /* Program text. */
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_start:
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movabs $SYS_write,%rax /* System call function: write, in %rax. */
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movabs $stdout,%rdi /* 1st parameter: file descriptor, in %rdi. */
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movabs $hello,%rsi /* 2nd parameter: address, in %rsi. */
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movabs $(bye-hello),%rdx /* 3rd parameter: byte count %rdx. */
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syscall /* Call system. */
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movabs $SYS_exit,%rax /* System call function: exit, in %rax. */
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movabs $0,%rdi /* 1st parameter: exit status, in %rdi. */
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syscall /* Call system. */
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hlt /* Should not be reached. */
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.data
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hello: .ascii "Hello, GNU Mes!\n"
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bye: .byte 0
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