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glibc/sysdeps/unix/sysv/linux/alpha/syscall.S
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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 <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) | |
* | |
* 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. | |
* | |
*/ | |
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 | |
call_pal PAL_callsys /* Invoke system call */ | |
bne a3, $error | |
ret | |
$error: | |
#ifndef PROF | |
br gp, 2f | |
2: ldgp gp, 0(gp) | |
#endif | |
SYSCALL_ERROR_HANDLER | |
END(__syscall) | |
weak_alias (__syscall, syscall) |