syscall.c

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/*
 * Copyright (C) 2005 Martin Decky
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <libc.h>

sysarg_t __syscall(const sysarg_t p1, const sysarg_t p2, 
                   const sysarg_t p3, const sysarg_t p4,
                   const syscall_t id)
{
        register sysarg_t __mips_reg_a0 asm("$4") = p1;
        register sysarg_t __mips_reg_a1 asm("$5") = p2;
        register sysarg_t __mips_reg_a2 asm("$6") = p3;
        register sysarg_t __mips_reg_a3 asm("$7") = p4;
        register sysarg_t __mips_reg_v0 asm("$2") = id;
        
        asm volatile (
                "syscall\n"
                : "=r" (__mips_reg_v0)
                : "r" (__mips_reg_a0),
                  "r" (__mips_reg_a1),
                  "r" (__mips_reg_a2),
                  "r" (__mips_reg_a3),
                  "r" (__mips_reg_v0)
                : "%ra" /* We are a function call, although C does not 
                         * know it */
        );
        
        return __mips_reg_v0;
}

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