mes/lib/linux/riscv64-mes-gcc/crt1.c

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/* -*-comment-start: "//";comment-end:""-*-
* GNU Mes --- Maxwell Equations of Software
* Copyright © 2017,2018,2019,2020 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
* Copyright © 2019,2020 Danny Milosavljevic <dannym@scratchpost.org>
* Copyright © 2021 W. J. van der Laan <laanwj@protonmail.com>
*
* 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/>.
*/
#include <mes/lib-mini.h>
//int main (int argc, char *argv[], char *envp[]);
/* gcc will generate the following preamble:
addi sp,sp,-16
sd s0,8(sp)
addi s0,sp,16
*/
// *INDENT-OFF*
void
_start ()
{
asm (
".option push\n\t"
".option norelax\n\t"
"lla gp, __global_pointer$\n\t"
".option pop\n\t"
"andi sp, sp, ~15\n\t" // make sure sp conforms to ABI alignment
);
asm (
"li t0, 0\n\t"
"mv %0, t0\n"
: "=r" (__stdin)
: //no inputs ""
);
asm (
"li t0, 1\n\t"
"mv %0, t0\n"
: "=r" (__stdout)
: //no inputs ""
);
asm (
"li t0, 2\n\t"
"mv %0, t0\n"
: "=r" (__stderr)
: //no inputs ""
);
// environ is &argv[argc + 1]
asm (
"lw t0, 0(s0)\n\t"
"addi t1, s0, 8\n\t"
"addi t0, t0, 1\n\t"
"slli t0, t0, 3\n\t"
"add %0, t1, t0\n\t"
: "=r" (environ)
: //no inputs ""
);
asm (
"lw a0, 0(s0)\n\t" // a0 argc
"addi a1, s0, 8\n\t" // a1 argv
"mv a2, %0\n\t" // a2 envp
"jal main\n\t"
"li a7, 93\n\t" // SYS_exit
"ecall\n\t" // exit(return value from main)
"ebreak\n\t"
: //no outputs ""
: "r" (environ)
);
}