1/* Copyright (C) 1996-2022 Free Software Foundation, Inc.
2   This file is part of the GNU C Library.
3
4   The GNU C Library is free software; you can redistribute it and/or
5   modify it under the terms of the GNU Lesser General Public
6   License as published by the Free Software Foundation; either
7   version 2.1 of the License, or (at your option) any later version.
8
9   The GNU C Library is distributed in the hope that it will be useful,
10   but WITHOUT ANY WARRANTY; without even the implied warranty of
11   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12   Lesser General Public License for more details.
13
14   You should have received a copy of the GNU Lesser General Public
15   License along with the GNU C Library.  If not, see
16   <https://www.gnu.org/licenses/>.  */
17
18#include <sysdep.h>
19
20/*
21 * This is for COMPATIBILITY with Linux/x86 only.  Linux/Alpha system
22 * calls return an error indication in a3.  This allows arbitrary 64bit
23 * values to be returned in v0 (because negative values are not
24 * mistaken as error numbers).  However, C allows only one value to
25 * be returned, so the interface below folds the error indication passed in
26 * a3 back into v0: it sets v0 to -errno if an error occurs.  Thus,
27 * no negative 64bit numbers can be returned.  To avoid this problem,
28 * use assembly stubs wherever possible/convenient.
29 *
30 * Usage:
31 *
32 * long	syscall(syscall_number, arg1, arg2, arg3, arg4, arg5, arg6)
33 *
34 * syscall_number = the index of the system call we're invoking
35 * arg1-arg6 = up to 6 integer arguments to the system call
36 *
37 * We need to do some arg shifting: the kernel expects the
38 * syscall number in v0 and the first six args in a0-a5.
39 *
40 */
41
42
43LEAF(__syscall, 0)
44#ifdef PROF
45	ldgp	gp, 0(pv)
46	.set noat
47	lda	AT, _mcount
48	jsr	AT, (AT), _mcount
49	.set at
50	.prologue 1
51#else
52	.prologue 0
53#endif
54
55	mov	a0, v0		/* Syscall number -> v0 */
56	mov	a1, a0		/* arg1-arg5 -> a0-a4 */
57	mov	a2, a1
58	mov	a3, a2
59	mov	a4, a3
60	mov	a5, a4
61	ldq	a5,0(sp)	/* arg6 -> a5 */
62
63	call_pal PAL_callsys	/* Invoke system call */
64	bne	a3, SYSCALL_ERROR_LABEL
65	ret
66
67PSEUDO_END(__syscall)
68
69weak_alias (__syscall, syscall)
70