63 lines
1.8 KiB
C
63 lines
1.8 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 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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// no clue what crt0.o is and why gcc-2.6.3 needs it
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// instead of calling main, it seems to call either _main or ___main,
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// let's try _main first
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char **environ = 0;
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int main (int argc, char *argv[]);
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// gcc x86_64 calling convention:
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// rdi, rsi, rdx, rcx, r8, r9, <stack0>, <stack1>
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void
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_start ()
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{
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asm (
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"movq %%rbp,%%rax\n\t"
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"add $8,%%rax\n\t"
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"movq (%%rax),%%rax\n\t"
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"add $3,%%rax\n\t"
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"shl $3,%%rax\n\t"
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"add %%rbp,%%rax\n\t"
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"mov %%rax,%0\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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"mov %rbp,%rax\n\t"
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"add $16,%rax\n\t"
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"mov %rax,%rsi\n\t"
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"mov %rbp,%rax\n\t"
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"add $8,%rax\n\t"
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"mov (%rax),%rax\n\t"
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"mov %rax,%rdi\n\t"
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"call _main\n\t"
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"mov %rax,%rdi\n\t"
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"mov $0x3c,%rax\n\t"
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"syscall \n\t"
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"hlt \n\t"
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);
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}
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