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/* Copyright (C) 1996-2021 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, see
<https://www.gnu.org/licenses/>. */
#include <sysdep.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, arg6)
*
* syscall_number = the index of the system call we're invoking
* arg1-arg6 = up to 6 integer arguments to the system call
*
* We need to do some arg shifting: the kernel expects the
* syscall number in v0 and the first six args in a0-a5.
*
*/
LEAF(__syscall, 0)
#ifdef PROF
ldgp gp, 0(pv)
.set noat
lda AT, _mcount
jsr AT, (AT), _mcount
.set at
.prologue 1
#else
.prologue 0
#endif
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
ldq a5,0(sp) /* arg6 -> a5 */
call_pal PAL_callsys /* Invoke system call */
bne a3, SYSCALL_ERROR_LABEL
ret
PSEUDO_END(__syscall)
weak_alias (__syscall, syscall)
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