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/* Copyright (C) 1996 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by David Mosberger <davidm@azstarnet.com>, 1996.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#include <features.h>
#include <asm/regdef.h>
#include <asm/pal.h>
/*
* This is for COMPATIBILITY with Linux/x86 only. Linux/Alpha system
* calls return an error indication in a3. This allows arbitrary 64bit
* values to be returned in v0 (because negative values are not
* mistaken as error numbers). However, C allows only one value to
* be returned, so the interface below folds the error indication passed in
* a3 back into v0: it sets v0 to -errno if an error occurs. Thus,
* no negative 64bit numbers can be returned. To avoid this problem,
* use assembly stubs wherever possible/convenient.
*
* Usage:
*
* long syscall(syscall_number, arg1, arg2, arg3, arg4, arg5)
*
* syscall_number = the index of the system call we're invoking
* arg1-arg5 = up to 5 integer arguments to the system call
*
* We need to do some arg shifting: the kernel expects the
* syscall number in v0 and the first five args in a0-a4.
*
*/
.globl __syscall;
.align 4;
.ent __syscall, 0;
__syscall:
.frame sp, 0, ra
.prologue 0
mov a0, v0 /* Syscall number -> v0 */
mov a1, a0 /* arg1-arg5 -> a0-a4 */
mov a2, a1
mov a3, a2
mov a4, a3
mov a5, a4
call_pal PAL_callsys /* Invoke system call */
bne a3, $error
ret
$error:
br gp, 2f
2: ldgp gp, 0(gp)
jmp zero,__syscall_error
.end __syscall
weak_alias (__syscall, syscall)
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