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/* Copyright (C) 1996 Free Software Foundation, Inc.
Contributed by David Mosberger (davidm@azstarnet.com).
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA. */
#include <sysdep.h>
/*
* This is for COMPATIBILITY with Linux/x86 only. Linux/Alpha system
* calls return an error indication in a3. This allows to return
* arbitrary 64bit values in v0 (because negative values are not
* mistaken as error numbers). However, C allows to return only one
* value 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)
bis a0, a0, v0 # Syscall number -> v0
bis a1, a1, a0 # arg1-arg5 -> a0-a4
bis a2, a2, a1
bis a3, a3, a2
bis a4, a4, a3
bis a5, 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
weak_alias(__syscall, syscall)
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