mes/lib/linux/x86_64-mes-gcc/crt1.c

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/* -*-comment-start: "//";comment-end:""-*-
* GNU Mes --- Maxwell Equations of Software
* Copyright © 2017,2018 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
*
* This file is part of GNU Mes.
*
* GNU Mes is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or (at
* your option) any later version.
*
* GNU Mes is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU Mes. If not, see <http://www.gnu.org/licenses/>.
*/
char **environ = 0;
int main (int argc, char *argv[]);
// gcc x86_64 calling convention:
// rdi, rsi, rdx, rcx, r8, r9, <stack0>, <stack1>
void
_start ()
{
asm (
"mov %%rbp,%%rax\n\t"
"add $8,%%rax\n\t"
"mov (%%rax),%%rax\n\t"
"add $3,%%rax\n\t"
"shl $3,%%rax\n\t"
"add %%rbp,%%rax\n\t"
"mov %%rax,%0\n\t"
"mov %%rax,%%rdx\n\t"
: "=r" (environ)
: //no inputs ""
);
asm (
"mov %rbp,%rax\n\t"
"add $16,%rax\n\t"
"mov %rax,%rsi\n\t"
"mov %rbp,%rax\n\t"
"add $8,%rax\n\t"
"mov (%rax),%rax\n\t"
"mov %rax,%rdi\n\t"
"call main\n\t"
"mov %rax,%rdi\n\t"
"mov $0x3c,%rax\n\t"
"syscall \n\t"
"hlt \n\t"
);
}