78 lines
2.2 KiB
C
78 lines
2.2 KiB
C
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/* -*-comment-start: "//";comment-end:""-*-
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* GNU Mes --- Maxwell Equations of Software
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* Copyright © 2017,2018,2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
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* Copyright © 2019,2020 Danny Milosavljevic <dannym@scratchpost.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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#include <mes/lib-mini.h>
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//int main (int argc, char *argv[], char *envp[]);
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/* Note: GCC automatically emits a preable in order to set up the frame pointer:
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"push {fp}"
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"add fp, sp, 0"
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*/
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// *INDENT-OFF*
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void
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_start ()
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{
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asm (
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"mov r0,#0\n\t"
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"mov %0,r0\n"
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: "=r" (__stdin)
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: //no inputs ""
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);
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asm (
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"mov r0,#1\n\t"
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"mov %0,r0\n"
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: "=r" (__stdout)
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: //no inputs ""
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);
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asm (
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"mov r0,#2\n\t"
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"mov %0,r0\n"
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: "=r" (__stderr)
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: //no inputs ""
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);
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/* environ = argv + argc + 1 */
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asm (
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"ldr r0,[fp,#4]\n\t" /* r0 = argc */
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"add r1,fp,#8\n\t" /* r1 = &argv[0] */
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"add r2,r0,#1\n\t" /* r2 = r0 + 1 */
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"lsl r2,#2\n\t" /* r2 = (r0 + 1) << 2 */
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"add r2,r2,r1\n\t" /* r2 = ((r0 + 1) << 2) + r1 */
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"push {r2}\n\t" /* envp */
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"push {r1}\n\t" /* argv */
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"push {r0}\n\t" /* argc */
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"mov %0,r2\n\t"
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: "=r" (environ)
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: //no inputs ""
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);
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asm (
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"ldr r0,[sp]\n\t" /* argc */
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"ldr r1,[sp, #4]\n\t" /* argv */
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"ldr r2,[sp, #8]\n\t" /* envp */
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"bl main\n\t"
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"mov r7, #1\n\t"
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"swi #0\n\t"
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"wfi \n\t"
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);
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}
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