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 $r0
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RET
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...
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*/
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/** Code: */
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SYS_exit = 1 /* Linux syscalls. */
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SYS_write = 4
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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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mov r7, $SYS_write /* System call function: write, in r7. */
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mov r0, $stdout /* 1st parameter: file descriptor, in r0. */
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add r1, pc, $(hello - here - 4) /* 2nd parameter: address, in r1. */
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here:
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mov r2, $(bye-hello) /* 3rd parameter: byte count r2. */
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swi 0 /* Call system. */
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mov r7,$SYS_exit /* System call function: exit, in r7. */
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mov r0,$0 /* 1st parameter: exit status, in r0. */
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swi 0 /* Call system. */
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wfi /* Should not be reached. */
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hello: .ascii "Hello, GNU Mes!\n"
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bye:
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