1 /* Copyright (C) 1996-2017 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by David Mosberger <davidm@azstarnet.com>, 1996.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library. If not, see
17 <http://www.gnu.org/licenses/>. */
22 * This is for COMPATIBILITY with Linux/x86 only. Linux/Alpha system
23 * calls return an error indication in a3. This allows arbitrary 64bit
24 * values to be returned in v0 (because negative values are not
25 * mistaken as error numbers). However, C allows only one value to
26 * be returned, so the interface below folds the error indication passed in
27 * a3 back into v0: it sets v0 to -errno if an error occurs. Thus,
28 * no negative 64bit numbers can be returned. To avoid this problem,
29 * use assembly stubs wherever possible/convenient.
33 * long syscall(syscall_number, arg1, arg2, arg3, arg4, arg5, arg6)
35 * syscall_number = the index of the system call we're invoking
36 * arg1-arg6 = up to 6 integer arguments to the system call
38 * We need to do some arg shifting: the kernel expects the
39 * syscall number in v0 and the first six args in a0-a5.
56 mov a0, v0 /* Syscall number -> v0 */
57 mov a1, a0 /* arg1-arg5 -> a0-a4 */
62 ldq a5,0(sp) /* arg6 -> a5 */
64 call_pal PAL_callsys /* Invoke system call */
65 bne a3, SYSCALL_ERROR_LABEL
70 weak_alias (__syscall, syscall)